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Optically Active Helical Substituted Polyacetylenes Showing Reversible Helix Inversion in Emulsion and Solution State
AbstractThis Communication reports two substituted polyacetylenes that can adopt helical structures of preferential screw sense in both emulsion (nanoparticle) and solution; however, the handedness of the macromolecular helices is just opposite in the two states. More interestingly, the helical screw sense of the polymers demonstrated a reversible transition between the two states. The unprecedented findings are of significant importance for acquiring new insights into helical polymers and for developing novel advanced chiral materials.  Substituted acetylene monomers undergo catalytic emulsion polymerization in aqueous media providing stable emulsion constituted by helical substituted polyactetylenes. Such helical polymers in emulsion demonstrate the opposite helicity when compared with the corresponding polymer solution.
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Zinc Ion Uniquely Induced Triple Shape Memory Effect of DipoleāDipole Reinforced Ultra-High Strength Hydrogels
AbstractIn this study, we demonstrate that dipoleādipole interaction can be employed to not only tremendously enhance the mechanical properties of hydrogel, but also impart the gel to an amazing ability to memorize two temporary shapes. Cross-linked hydrogels synthesized by copolymerization of acrylonitrile, a dipoleādipole containing monomer and hydrophilic comonomer are shown to exhibit triple shape memory (SM) triggered by the dynamic association and dissociation of dipoleādipole pairing between cynao groups uniquely responding to zinc ion species and concentration. This approach contributes to design and fabrication of novel SM hydrogels in a distinct way from conventional SM materials.  Acrylonitrile is not just for fiber: A dipoleādipole reinforced (DDR) ultrahigh strength hydrogel exhibiting triple shape memory effect has been fabricated for the first time by copolymerizing acrylonitrile with hydrophilic monomer. This strategy contributes to the discovery of a new type of shape memory hydrogels driven by Zn2+-responsive dynamic change of dipoleādipole interaction.
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Learning From Nature: Synthesis and Characterization of Longitudinal Polymer Gradient Materials Inspired by Mussel Byssus Threads
AbstractMarine mussels use their threads for attachment to any substratum and these biopolymer gradient fibers show an excellent combination of stiff and soft mechanical properties. A straightforward approach for the preparation of macroscopic longitudinal polymer gradient materials on the centimeter scale based on a poly(dimethyl siloxane) system is presented. Compositional gradients are realized by using three syringe pumps feeding different prepolymers capable to undergo thermal cross-linking. Within the gradient samples, the stiffness between the hard and soft part can be varied up to a factor of four. The gradients are analyzed by UVāVis spectroscopy as well as compressive and tensile modulus testing.  A straightforward approach is presented for the preparation of bioinspired, macroscopic polymer gradient materials. Compositional gradients are realized using three syringe pumps feeding different prepolymers capable of cross-linking. The stiffness within the gradient sample can be varied up to a factor of four. By addition of a dye to one component, the gradient structure can be visualized.
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Tuning Fluorescent Response of Nanoscale Film With Polymer Grafting
AbstractAn effective method for tuning fluorescent response of an ultrathin (5 nm) polymer film, which can be used for generation of sensing arrays, is reported. This method is distinctive in that the modification of the optical response is achieved with polymer grafting of a non-fluorescent polymer to a fluorescent film. Using this approach, a number of films demonstrating different fluorescent emission when exposed to solvent vapors were synthesized.  An effective method for tuning fluorescent response of an ultrathin (5 nm) polymer film is reported. The ultrathin fluorescent polymer film anchored to a solid surface changes its fluorescence response if a non-fluorescent polymer of another nature is attached to its surface via covalent grafting.
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A Facile Route to Reassemble Titania Nanoparticles Into Ordered Chain-like Networks on Substrate
AbstractA facile route to reassemble titania nanoparticles within the titania-block copolymer composite films has been developed. The titania nanoparticles templated by the amphiphilic block copolymer of poly(styrene)-block-poly (ethylene oxide) (PS-b-PEO) were frozen in the continuous PS matrix. Upon UV exposure, the PS matrix was partially degraded, allowing the titania nanoparticles to rearrange into chain-like networks exhibiting a closer packing. The local structures of the Titania chain-like networks were investigated by both AFM and SEM; the lateral structures and vertical structures of the films were studied by GISAXS and X-ray reflectivity respectively. Both the image analysis and X-ray scattering characterization prove the reassembly of the titania nanoparticles after UV exposure. The mechanism of the nanoparticle assembly is discussed.  Titania nanoaparticles within the PS-b-PEO block copolymer composite films are reassembled into chain-like networks by simple UV exposure. The titania nanoparticles are frozen in the polymer matrix composed of the PS block after film deposition. Upon UV treatment, the PS matrix is partially removed, allowing the nanoparticles to move close to each other and pack close together.
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Live Monitoring of Cargo Release From Peptide-Based Hybrid Nanocapsules Induced by Enzyme Cleavage
AbstractThe miniemulsion process is used as a new route for the preparation of enzyme-responsive nanocapsules with payload-release properties. Peptide-based hybrid nanocapsules are prepared via interfacial polyaddition containing a water-soluble dye that is efficiently encapsulated inside. The influence of the synthetic parameters as the functionality of the peptide and the nature of the dispersed phase on the structure of the nanocapsules were investigated. After redispersion in water, the enzymatic cleavage of the peptide sequence and the release of the fluorescent dye are both monitored in real time. This is evidenced because of the quenching FRET system framing the recognition site in the peptide sequence, and the fluorescence recovery of the self-quenched encapsulated dye respectively.  Preparation of peptide-based hybrid nanocapsules is achieved via interfacial polyaddition in miniemulsion. A fluorescent dye is encapsulated at concentrations at which self-quenching occurs and is released after enzymatic cleavage of the peptide. The degradation of the capsules and release of the dye are monitored in real time with optical means (FRET) and fluorescence recovery.
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Functionalized Nanoporous Thin Films From Photocleavable Block Copolymers
AbstractA polystyrene-block-poly(ethylene oxide) block copolymer bearing a photocleavable junction between the blocks is used to form nanoporous thin films with carboxylic acid functions homogeneously distributed on the pore walls. The presence of the carboxylic acid groups is evidenced by fluorescence spectroscopy after their reaction with a diazomethane functionalized fluorescent dye. In addition, the initial light-responsive thin film, acting as a photoresist, can be easily patterned to selectively generate porosity in predetermined areas. In that way, fluorescent patterns can be obtained as evidenced by fluorescent microscopy.  A PS-b-PEO block copolymer bearing a photocleavable junction between the blocks is used to form nanoporous thin films with carboxylic acid functions homogeneously distributed on the pore walls. The initial light-responsive thin film, acting as a photoresist, can be easily patterned to selectively generate porosity in predetermined areas.
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Synthesis of High Molecular Weight Polyesters via In Vacuo Dehydrogenation Polymerization of Diols
AbstractThe Milstein catalyst has proven to be highly effective for the conversion of alcohols to esters, as well as alcohols and amines to amides and polyamides. We have recently found that the catalyst's range can be extended to very efficient in vacuo dehydrogenation polymerization of Ī±,Ļ-diols to generate polyesters. The gaseous hydrogen byproduct that is produced is easily removed to drive the equilibrium toward product, which leads to the formation of high molecular weight polymer ( up to 145 000 g molā1). This optimized methodology works well to polymerize diols with a spacer of six carbons or more. Diols with fewer carbons are cyclized to lactone; the dividing point is the dehydrogenation of 1,5-pentanediol, which leads to a mixture of polyester and lactone. Reported herein is the synthesis and characterization of five aliphatic polyesters prepared via this novel dehydrogenation polymerization approach.  Ī±,Ļ-Diols with a spacer of six or more carbons are effectively converted to high molecular weight polyesters through a dehydrogenative polymerization catalyzed by the Milstein catalyst. Performing the reaction in vacuo yields higher molecular weight polymer than that produced by purging the polymerization with inert gas. Number- averaged molecular weights approaching 150 000 g molā1 are accessible using this polycondensation.
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Photodegradable Polymers for Biotechnological Applications
AbstractPhotodegradable polymers constitute an emerging class of materials that finds numerous applications in biotechnology, biomedicine, and nanoscience. This article highlights some of the emerging applications of photodegradable polymers in the form of homopolymers, particles and self-assembled constructs in solution, hydrogels for tissue engineering, and photolabile polymers for biopatterning applications. Novel photochemistries have been combined with controlled polymerization methods, which result in well-defined photodegradable materials that exhibit light mediated and often controlled fragmentation processes.  Let there be light. Photodegradable polymers in the form of self-assembled constructs, polymer networks, and surfaces are discussed with regards to their potential uses in biotechnological applications such as controlled drug delivery, photolithography, and biopatterning.
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Macromol. Rapid Commun. 3/2012
Back Cover: Micelles from thermoresponsive P(S-b-NIPAM-b-S) triblock copolymers show a decrease of their radius and subsequent aggregation when heated above the cloud point of PNIPAM. Time-resolved small-angle neutron scattering during a temperature jump unravels the kinetics of these processes and allows a quantitative description of the collapse and the aggregation. Further details can be found in the article by J. Adelsberger, E. Metwalli, A. Diethert, I. Grillo, A. M. Bivigou-Koumba, A. Laschewsky, P. MĆ¼ller-Buschbaum, and C. M. Papadakis* on page 254. |
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Living Polymerization via Anionic Initiation for the Synthesis of Well-Defined PPV Materials
AbstractThe anionic polymerization of PPV via the sulfinyl precursor route is further investigated. When LHMDS is employed as the base to form the actively propagating quinodimethane system and THF as the solvent, anionic polymerizations can be observed. With the use of tert- butyl-substituted anionic initiators, specific functional groups can be built in the polymer chain and the chain length can be efficiently controlled, which is demonstrated here for the first time. With introduction of branched side chains on the aromatic core, soluble conjugated PPV material can be obtained with molecular weights in the range of 5000ā16 000 g molā1.  A synthesis route for well-defined poly(p- phenylene vinylene) (PPV) materials is presented. Anionic polymerization conditions are achieved via selection of reaction conditions and the molecular weight is efficiently controlled by introduction of dedicated anionic initiators. Soluble PPVs with comparatively narrow molecular weight distributions in the weight range of 6 to 20 kDa were obtained.
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Macromol. Rapid Commun. 3/2012
Front Cover: Marine mussels use their threads for attachment to any substratum and these biopolymer gradient fibers show an excellent combination of stiff and soft mechanical properties. A straightforward approach is presented for the preparation of bioinspired macroscopic longitudinal polymer gradient materials on the centimeter scale based on a poly(dimethyl siloxane) system. Fur-ther details can be found in the article by K. U. Claussen, R. Giesa, T. Scheibel, and H.-W. Schmidt* on page 206. Cover image courtesy of Genevieve Anderson. |
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Beyond Orientation: The Impact of Electric Fields on Block Copolymers
AbstractSince the first report on electric field-induced alignment of block copolymers (BCPs) in 1991, electric fields have been shown not only to direct the orientation of BCP nanostructures in bulk, solution, and thin films, but also to reversibly induce orderāorder transitions, affect the orderādisorder transition temperature, and control morphologies' dimensions with nanometer precision. Theoretical and experimental results of the past years in this very interesting field of research are summarized and future perspectives are outlined.  Since 1991, electric fields have been shown to strongly affect block copolymer structures. Aside from alignment, morphological distortions, orderāorder, and orderādisorder transitions have been described both in bulk and thin films. Important findings of the last two decades are summarized and perspectives for future progress in the field of block copolymers in electric fields are outlined.
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Preparation and Characterization of Anisotropic Submicron Particles From Semicrystalline Polymers
AbstractThe synthesis of colloidally stable submicron particles of syndiotactic polystyrene (sPS) and isotactic polystyrene (iPS) is reported. Model particles based on poly-L-lactic acid (PLLA), atactic polystyrene (aPS), sPS, and iPS are prepared by the evaporation of a solvent present in miniemulsion droplets. The degree of crystallinity of the particles is found to decrease with their size, as shown by DSC and WAXS measurements. Remarkably, nonspherical particles can be formed in the dispersed state with sPS and iPS, whereas PLLA and aPS particles always display spherical morphologies.  Syndiotactic polystyrene particles with significant anisotropy are prepared from a miniemulsionāsolvent evaporation process. The crystallinity increases with increasing particle diameter. For PLLA, it is possible to control the crystallinity of the particles by a thermal treatment of the dispersions.
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Nanoporous Gold Film Prepared by the Epoxidation of Poly(styrene-b-butadiene) Diblock Copolymer Templated Micelles
AbstractA new approach is developed for the preparation of nanoporous gold (Au) films using diblock copolymer micelles as templates. Stable Au nanoparticles (NPs) with a narrow distribution are prepared by modifying NPs functionalized with 4-(dimethylamino)pyridine ligands (DMAP Au NPs) and a spherical micelle formed through the epoxidation of poly(styrene-b-butadiene) diblock copolymer to produce poly(styrene-b-vinyl oxirane) (PS-b-PBO) in tetrahydrofuranāacetonitrile solution. The exchange reaction of 4-aminothiophenol of PS-b-PBO diblock copolymer micelles with DMAP Au NPs can produce block copolymerāAu NPs composite films. After the pyrolysis of the diblock copolymer templates at a specific temperature to avoid the collapse of the Au NPs, a nanoporous Au film is prepared.  A new approach is developedfor the preparation of nanoporous gold (Au) films using diblock copolymer (PS-b-PBO) micelles as templates. After the pyrolysis of the diblock copolymer templates at a specific temperature to avoid the collapse of the gold nanoparticles, a nanoporous Au film is prepared.
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Thermotropic Mesomorphism via Self-Assembly of Cationic Dendritic Polymers with an Anionic Polar Carboxylic Acid
AbstractThe synthesis and characterization of ionic liquid crystalline dendritic polymers based on the ammonium salts of commercially available poly(propylene imine) (PPI), poly(amidoamine) (PAMAM), poly(ethyleneimine) (PEI), and the fully methylated PEI (PEIMe) with 5-(4-cyanobiphenoxy)pentanoic acid (CBPA) are reported. The occurrence of proton transfer from the carboxylic acid to the amine groups is confirmed using IR and NMR techniques. The mesomorphic behavior is investigated by means of differential scanning calorimetry, polarizing optical microscopy, and X-ray diffractometry. Although CBPA exhibits monotropic nematic mesomorphism, all ionic complexes display enantiotropic liquid crystal properties. The relationship between the mesomorphism of the complexes and their structure is discussed.  Ionic liquid crystalline dendrimers and hyperbranched polymers are obtained by a proton transfer reaction between a polar carboxylic acid and the amine groups of the dendritic polymers. Both the chemical structure of the mesogenic unit and the scaffold of the dendritic polymer exert an influence on the supramolecular self-assembly of these macromolecules and they self-assemble in different mesophases.
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Liquid Crystalline Polythiophenes With Amphiphilic Side Chains
AbstractA series of poly(thiophene) derivatives with decyl-oligo(oxyethylene) side groups, (PDnET) is synthesized via oxidative coupling polymerization. PD3ET and PD4ET with longer oligo(oxyethylene) units exhibited a liquid crystalline phase with well-ordered lamella structures, although PD3ET showed a more ordered structure than PD4ET. PD1ET and PD2ET have shorter oligo(oxyethylene) groups than PD3ET and show less-ordered structures with liquid-crystalline phase observed. The UV-vis spectra indicated that the maximum absorption wavelengths of PDnET increase when the number of oxyethylene units increases from 1 to 3; however, the maximum absorption wavelength of PD4ET is lower than that of PD3ET. Therefore, the most ordered and conjugated structures are obtained when the number of oxyethylene units is three.  PDnETs have ordered layer structure and the d-spacing values of the long period increase almost linearly as the number of ethylene oxide units increases from one to four. The intensities of the (100) peak related to layer spacing for PD3ET and PD4ET are much more intense than those for PD1ET and PD2ET indicating that PD3ET and PD4ET have more ordered layer structures.
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Macromol. Chem. Phys. 3/2012
Front Cover: As schematically shown in the cover, polymers in electric fields have been extensively studied during the last twenty years. While first, only the alignment of structures was investigated, order-order and order-disorder transitions (amongst others) have been found since. Cover designed by C.W. Pester. Further details can be found in the article by C. Liedel, C. W. Pester, M. Ruppel, V. S. Urban, and A. Bƶker* on page 259. |
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Molecular Weight Distribution Characteristics (of a Polymer) Derived from a Stretched-Exponential PGSTE NMR Response FunctionāSimulation
AbstractAssuming the signal response in a pulsed gradient stimulated echo (PGSTE) experiment (on a polymer) to be described by a simple stretched-exponential function (SEF) and knowing the scaling law between diffusivity and molecular weight, the molecular weight distribution (MWD) characteristics (kurtosis, skewness, moment, and width) are derived and compared to the corresponding distribution characteristics obtained by a log-normal function fit (to the same MWD). Also, the challenge involved in obtaining a reliable weight average molecular weight from an SEF response function is discussed.  The response from a pulsed gradient stimulated echo NMR experiment on a polymer in solution is found to be approximated by a stretched exponential function. By performing an inverse Laplace transform, the molecular weight distribution is obtained. The relationship between the molecular weight distribution and a log-normal distribution is discussed.
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New Improved Thermosets Obtained From Diglycidylether of Bisphenol A and a Multiarm Star Copolymer Based on Hyperbranched Poly(glycidol) Core and Poly(methyl methacrylate) Arms
AbstractA well-defined multiarm star copolymer, hyperbranched poly(glycidol)-b-poly(methyl methacrylate) (PGOH-b-PMMA), is used as a modifier in the curing of diglycidylether of bisphenol A (DGEBA) using 1-methyl imidazole (1MI) as anionic initiator. The effect of the polymer topology on the curing and gelation processes is studied. The addition of the PGOH-b-PMMA to the resin leaves the complex viscosity unaltered. The addition of the modifier decreases the shrinkage after gelation compared to that measured in the curing of the neat resin. By DMTA a single relaxation process in the pure DGEBA and modified thermoset is found. The addition of the star-like modifier led to an improvement on the mechanical characteristics such as the impact strength and microhardness in comparison to the neat material.  A well-defined multiarm star copolymer, hyperbranched poly(glycidol)-b-poly(methyl methacrylate) (PGOH-b-PMMA) is used as modifier in the curing of diglycidylether of bisphenol A (DGEBA). The addition of PGOH-b-PMMA leaves the complex viscosity unaltered. The shrinkage after gelation and the mechanical characteristics are improved compared to the neat formulation. |
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VUV-Induced Photopolymerization of Acrylates
AbstractAcrylates and methacrylates are photopolymerized without photoinitiator by exposure to 172 nm radiation. The kinetics of the polymerization is studied using real-time Fourier-transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy. It is shown that layers with a thickness of ā500 nm can be polymerized very rapidly. The effect of structure, viscosity, functionality, and absorption of the acrylates as well as the influence of temperature and oxygen concentration on the reactivity are studied. A strong conversion gradient is observed in layers up to ā2 Ī¼m thickness, which reflects the intensity gradient within the layer. However, the penetration of the polymerization into the layer exceeds the initial penetration depth of the VUV radiation, which indicates strong bleaching of the acrylates during irradiation.  Acrylates and methacrylates can be photopolymerized without photoinitiator using 172 nm radiation. Real-time FTIR-ATR spectra show that layers with ā500 nm thickness can be polymerized rapidly. The penetration of the polymerization into the layer was found to exceed the initial penetration depth of the VUV radiation, which indicates bleaching of the acrylates during irradiation.
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Synthesis and Characterization of Poly(acrylic acid) Brushes: āGrafting-Ontoā Route
AbstractA guideline for the synthesis of poly(acrylic acid) brushes on planar silica surfaces by the āgrafting-ontoā approach is described. It is demonstrated that some thermal precautions must be taken to obtain extended brushes. It is also shown that neutron reflectivity is well suited for the characterization of each step of the synthesis, while it is (unfortunately) rarely used for that purpose. The steps are the following: first, the substrates are covered with a self-assembled monolayer of epoxy-terminated molecules; then, the poly(tert-butyl acrylate) brushes are built using preformed and end-functionalized chains; finally, the deprotection of the ester group is performed using a pyrolysis reaction to convert the poly(tert-butyl acrylate) brushes into poly(acrylic acid) brushes.  A guideline for the synthesis of poly(acrylic acid) brushes on planar silica surfaces by the āgrafting-ontoā approach is described. Characterization determines the best conditions to obtain extended brushes. The cleavage of chains and the formation of loops during the grafting of end-functionalized poly(tert-butyl acrylate) chains can be prevented if thermal precautions are taken.
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Tunable Nanometer-Scale Architecture of OrganicāInorganic Hybrid Nanostructured Materials for Structural and Functional Applications
AbstractDirect crystallization of polymer crystals along the long axis of carbon nanotubes (CNTs) to produce a hybrid nanostructured material is expected to retain the properties of CNTs and has the advantage of a strong polymer/CNT interface. Three different polymer systems are selected to elucidate the fundamental principles that govern the processing of organicāinorganic hybrid nanostructured materials with nanometer-scale architecture. The tunable character of the nanometer-scale hybrid architecture is investigated as a function of undercooling and polymer concentration. It is observed that while polyethylene and nylon 6,6 crystallize in a periodic manner as disk-shaped crystals along the long axis of the CNTs, the polypropyleneāCNTs result in conventional spherulites. The reasons for these differences are analyzed.  The synthesis of tunable nanometer-scale architecture of organicāinorganic hybrid materials involves direct crystallization of polymers along the long axis of carbon nanotubes (CNTs), which produces a strong polymer/CNT interface. The spacing between periodic polymer crystals is tuned by changing undercooling conditions.
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Well-defined N-Isopropylacrylamide Dual-Sensitive Copolymers with LCST ā38 Ā°C in Different Architectures: Linear, Block and Star Polymers
AbstractReversible addition-fragmentation chain transfer (RAFT) polymerization is used to prepare temperature- and pH-sensitive statistical copolymers with lower critical solution temperature (LCST) close to 38 Ā°C at pH 7.4 based on N-isopropylacrylamide and methacrylic acid derivative comonomers with a pKa close to 6. Statistical copolymers are re-activated to prepare amphiphilic block copolymers and star polymers with cross-linked core. The LCST is maintained by varying the architecture; however, the LCST originated behaviour changes due to self-aggregation. Statistical copolymers and short block copolymers show complex aggregation, whereas mid-size block copolymers and star polymers show shrinkage of aggregate dimensions. The pH of the medium has a profound impact on the self-assembling behaviour of the different polymer architectures.  Statistical, block and star polymers with lower critical solution temperature (LCST) close to 38 Ā°C at pH 7 to 7.4 are prepared using RAFT copolymerization of NIPAAm with acidic comonomers. Statistical copolymers and short block copolymers show complex aggregation, whereas mid-size block copolymers and star polymers show shrinkage of aggregate dimensions. pH impacts stronlgy the LCST.
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Macromol. Chem. Phys. 3/2012
Back Cover: A new approach for preparation of gold nano-porous films was prepared from Au nanoparticles under-going an exchange reaction with PS-b-PBO micelles in solutions to form a block copolymer/Au composite. After the pyrolysis of the block copolymer templates at a specific temperature to avoid the collapse of the gold nanoparticles, a nanoporous gold film was formed. The materials that were fabricated by this method have potential applications as modified electrodes. Further details can be found in the article by S.-W. Kuo,* H.-Y. Yang, C.-F. Wang, and K.-U. Jeong on page 344. |
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Kinetics of Collapse Transition and Cluster Formation in a Thermoresponsive Micellar Solution of P(S-b-NIPAM-b-S) Induced by a Temperature Jump
AbstractStructural changes at the intra- as well as intermicellar level were induced by the LCST-type collapse transition of poly(N-isopropyl acrylamide) in ABA triblock copolymer micelles in water. The distinct process kinetics was followed in situ and in real-time using time-resolved small-angle neutron scattering (SANS), while a micellar solution of a triblock copolymer, consisting of two short deuterated polystyrene endblocks and a long thermoresponsive poly(N-isopropyl acrylamide) middle block, was heated rapidly above its cloud point. A very fast collapse together with a multistep aggregation behavior is observed. The findings of the transition occurring at several size and time levels may have implications for the design and application of such thermoresponsive self-assembled systems.  Micelles from thermoresponsive P(S-b -NIPAM-b-S) triblock copolymers show a decrease of their radius and subsequent aggregation when heated above the cloud point of PNIPAM. Time-resolved SANS during a temperature jump unravels the kinetics of these processes and allows a quantitative description of the collapse and the aggregation, which is found to involve several steps.
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Internal Architecture of Zwitterionic Polymer Brushes Regulates Nonfouling Properties
AbstractIn this work, we study how film thickness and chain packing density affect the protein-resistant properties of polymer brushes in complex media. Polymer brushes based on dual-functional poly(carboxybetaine acrylamide) (pCB) were prepared via surface-initiated photoiniferter-mediated polymerization. By adjusting UV radiation time and solvent polarity, pCB films with different thicknesses can be achieved and characterized using an ellipsometer. The packing density of pCB polymer chains is directly related to the swelling ratio of swollen to collapsed film thicknesses. Results showed that the dry film thickness alone, used often in the literature, is not sufficient to correlate with nonfouling properties and the chain packing density must be considered for the design of nonfouling surface coatings.  The effects of film thickness and chain packing density on protein-resistant properties of poly(carboxybetaine acrylamide)-based polymer brushes in complex media were investigated. Through adjusting polymerization time and solvent polarity, we found that the internal architecture plays an important role in the nonfouling properties of surface coatings in addition to the dry film thickness.
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Nanocomposites Based on Layered Silicates and Epoxy Resins: Measurement of Clay Dispersion and Exfoliation using TEM, Solid-State NMR, and X-ray Diffraction Methods
AbstractIn an epoxy/layered silicate nanocomposite containing different organically modified layered silicats, the effect of various organic modifications and the layered silicate content on the layer distances are investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD) measurements, and 1H solid-state NMR. TEM micrographs were evaluated using a semi-quantitative method. The effect of paramagnetic impurities present in the clay is used to obtain overall sample information related to the degree of exfoliation by 1H solid-state NMR. A new model for determination of the degree of exfoliation by proton longitudinal relaxation rate measurements is developed.  The layer distances of organically modified layered silicates in an epoxy matrix can be influenced by variation of both layered silicate modification and content. These effects are investigated by transmission electron microscopy, X-ray diffraction measurements, and 1H solid-state NMR spectroscopy.
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Fe(0) Powder/CuBr2-Mediated āLivingā/Controlled Radical Polymerization of Methyl Methacrylate and Styrene at Ambient Temperature
AbstractThe combination of zero-valent iron (Fe(0) powder) and copper(II) bromide was used to mediate the polymerization of methyl methacrylate (MMA) or styrene (St) at 25 Ā° C. The results demonstrated that the solvent played an important role on the polymerization rate and molecular-weight control. The polymerization in toluene displayed a poorly controlled process with remarkably low polymerization rate. With dimethyl sulfoxide (DMSO) as solvent, the polymerization proceeded in a relatively high rate, and the number-average molecular weights were controlled especially at higher conversion. High conversions (80%) of St could be achieved with narrow molecular weight distributions in DMSO at 25 Ā°C. It was supposed that Fe(0) played a dual role, the activator for the generation of active radical and the reducing agent for CuBr2.  In this work, Fe(0) powder/CuBr2 is used to catalyze the polymerizations of MMA or St at 25 Ā°C. The solvent exerts a crucial effect on the polymerization profiles: DMSO offers a higher polymerization rate and a better control in comparison with toluene. Importantly, the polymerization of St can reach up to 80% conversion in DMSO at 25 Ā°C.
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Synthesis of Ī²-Cyclodextrin Containing Copolymer via āClickā Chemistry and Its Self-Assembly in the Presence of Guest Compounds
AbstractWe report the synthesis of a hydrophilic copolymer with one polyethylene glycol (PEG) block and one Ī²-cyclodextrin (Ī²-CD) containing block by a āclickā reaction between azido-substituted Ī²-CD and propargyl flanking copolymer. 1H NMR study suggested a highly efficient conjugation of Ī²-CD units by this approach. The obtained copolymer was used as a host macromolecule to construct assemblies in the presence of hydrophobic guests. For assemblies containing a hydrophobic polymer, their size can be simply adjusted by simply changing the content of hydrophobic component. By serving as a guest molecule, hydrophobic drugs can also be loaded accompanying the formation of nanoparticles, and the drug payload is releasable. Therefore, the copolymer synthesized herein can be employed as a carrier for drug delivery.  The synthesis of Ī²-cyclodextrin containing block copolymer via a āclickā reaction is reported. The self-assembly of this newly synthesized copolymer in the presence of guest compounds can lead to the formation of coreāshell structured nanoparticles. These assemblies can be employed as novel delivery vehicles for therapeutics.
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Helical Polymer as Mimetic Enzyme Catalyzing Asymmetric Aldol Reaction
AbstractThis Communication reports optically active helical substituted polyacetylenes which solely catalyzed asymmetric Aldol reaction between cyclohexanone and p-nitrobenzaldehyde; more importantly the helical structures are found to play crucial roles in the asymmetric catalysis, with a remarkable yield and ee (both up to 80%). A synergic effect is observed between the helical structures in the polymer main chains and the pendent prolinamide moieties for successfully catalyzing the asymmetric reaction. The role of the helical polymer backbones is further verified by tuning the relative helical structure content.  Synthetic helical polymers containing pendent prolineamide moieties efficiently catalyze the asymmetric aldol reaction between cyclohexanone and p-nitrobenzaldehyde. Both the product yield and ee can be up to 80%. Helical structures in the copolymer backbones are indispensable for the asymmetric catalysis. An increase in helical structure content leads to better catalysis effects.
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Effects of Block Length in Copolymers Based on Regioregular Oligothiophenes Linked With Electron-Accepting Units
AbstractCopolymers with an alternating structure of regioregular oligo(3-hexylthiophene) (O3HT) with different lengths and 2,5-dibutyl-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (DPP) were synthesized through Stille coupling reaction. The light absorption of the copolymers can be rationally tuned to have a broad spectrum across the visible region by adjusting the length of O3HT. Organic solar cells fabricated with the copolymers and PCBM showed a broad photoresponse and a comparable efficiency to that of poly(3-hexylthiophene) (P3HT):PCBM cells. The external quantum efficiency and fluorescence spectra suggested that the intrachain energy transfer from the O3HT block to the vicinity of the DPP unit could limit the photovoltaic performance of the copolymers.  O3HTāDPP with an alternating structure of regioregular O3HT and DPP accepting unit is synthesized. A broad light absorption across the visible range can be realized by tuning the length of O3HT. The photovoltaic efficiency of this copolymer (3.17%) is limited to a level similar to that of regioregular P3HT, which could be due to intrachain energy transfer.
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Ion-Specific Self-Assembly of Low-Dimension Aggregate Structures of Conjugated Polymer at Two-Phase Interface
AbstractA novel and facile approach to manipulate the morphology of Cu2+-ion-specific assembly of conjugated polymer by coordinative interaction at an oilāwater two-phase interface is present. The application of increasing importance is the use of Ļ-conjugated polymers as receptors, exploiting their ability to selectively form complexes, which can obviously change the optical properties in solution and induce the formation of varied solid nano/microstructures. By this method, microtubes are formed through self-rolling of a strained ionic bilayer film at the oil/water interface.  Cu2+-ion-specific assemblyof Ļ-conjugated polymer at oilāwater interface is studied, taking advantage of the cooperatively coordinating ability of relatively hydrophilic glycol chains. Self-rolling of the strained ionic bilayer that is formed at the ethyl acetateāwater interface leads to the formation of microtubes of polymerāCu2+ complex, so as to minimize the surface energy.
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Biological Glucose Metabolism Regulated Peptide Self-Assembly as a Simple Visual Biosensor for Glucose Detection
AbstractA glucose oxidase (GOx)-mediated glucose metabolism was in vitro mimicked and employed to regulate the self-assembly of peptide-based building blocks. In this new stimuli-responsive self-assembly system, two peptide-based building blocks, respectively, having aspartic acid (gelator 1) and lysine (gelator 2) residues were designed and prepared. When adding glucose and GOx to the aqueous solution of gelator 1 or the self-assembled fibrillar hydrogel of gelator 2 to construct glucose metabolism system, the metabolic product (gluconic acid) can trigger the protonation of the peptide molecules and induce the phase transitions of gelators 1 (sol-gel) and 2 (gel-sol). Because this glucose metabolism regulated peptide self-assembly is built on the oxidation of glucose, it can be used as a simple visual biosensor for glucose detection.  Peptide building blocks with self-assembly ability which could be regulated by a biological glucose metabolism were designed and synthesized. As the metabolic product, gluconic acid can trigger the protonation of peptide and induce phase transition. Because the glucose metabolism regulated self-assembly is based on the oxidation of glucose, it can be used as a visual biosensor for glucose detection.
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Solubilization of a Ļ-Conjugating Hydrophobic Dendrimer in Aqueous Media
AbstractPhenylazomethine dendrimers, which can be used as the template for precise metal nanoparticles, are soluble only in aprotic media. The use of a specific surfactant enabled their solubilization in aqueous solutions. Under dilute condition, they formed discrete micelles with a size close to the that of the dendrimer. Condensation resulted in their aggregation; however, they remained in a homogeneous solution without precipitation. Furthermore, each micelle was well isolated. The triplet-excited state of the zinc porphyrin core in the micelles was significantly stable, suggesting the formation of rigid core-shell micelles preventing any external molecules from approaching to the core.  Hydrophobic dendrimers were successfully dissolved in an aqueous solution by specific surfactant molecules. The resulting micelles exhibited a significantly high encapsulation effect for the contained dendrimer core. The triplet-excited state lifetime of the zinc porphyrin core in the micelle was 50 times longer than that of dendrimer itself in THF.
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Thermal and Photochemical Crosslinking of Hyperbranched Polyphenylene With Organic Azides
AbstractHere, we report on the first example of crosslinking (CL) hyperbranched polyphenylene (hbāPPh) with a small molecule crosslinker 1,3,5-tris(azidomethyl)benzene (TAMB). It was successfully shown that CL of the hbāPPh/TAMB (9:1) film is possible either thermally or photochemically making use of fundamentally different reaction mechanisms. Starting from a model reaction to prove the feasibility of the thermal CL reaction, we went on to check both the thermal and the photochemical crosslinkability of micrometer thick films. IR spectroscopy was furthermore used to confirm the CL process. Finally, the thin film morphology of the films before and after CL was investigated by AFM, revealing that the surface morphology was unaffected by the CL processes.  The first example of crosslinking (CL)hyperbranched polyphenylene in a thermal and in photochemical manner is demonstrated. An organic azide was added, which either reacts thermally with alkyne groups throughout a cycloaddition reaction or via nitrene addition to benzene rings upon photolysis of the azide groups. The CL process was investigated by dissolution studies, IR spectroscopy, and AFM.
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Polymer Nanostructures Made by Scanning Probe Lithography: Recent Progress in Material Applications
AbstractScanning probe lithography (SPL) is a series of techniques that utilizes a scanning probe or an array of probes for surface patterning. Recent developments of new material systems and patterning approaches have made SPL a promising, low-cost, bench-top, and versatile tool for fabricating various polymer nanostructures, with extraordinary importance in physical sciences, life sciences and nanotechnology. This feature article highlights the recent progress in four material applications: polymer resists, polymeric carriers for patterning functional materials, electronically active polymers and polymer brushes for tailoring surface morphology and functionality. An overview of future possibilities, with regard to challenges and opportunities in this field, is given at the end of the paper.  The latest developments in the fabrication of polymer nanostructures using scanning probe lithography (SPL) are highlighted, with special categorization by different material applications into polymer resists, polymeric carriers for functional materials, electronically active polymers and polymer brushes. The attributes of SPL in patterning polymer nanostructures are also summarized.
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Anisotropic Ionic Mobility of Lithium Salts in Lamellar Liquid Crystalline Polymer Networks
AbstractNew mesogens presenting smectic A (SmA) phases and capable of hosting lithium salts are designed. The mesogens comprise a vinyl-functionalized spacer to allow further reaction to the polymer backbone, an aromatic core and ethylene oxide chains, able to coordinate lithium ions. Copolymerizing these monomers with a suitable crosslinker yields the first lithium containing liquid crystalline elastomers (LCEs). The SmA structure where the ethylene oxide chains are microphase separated in layers is fixed by the crosslinking and permanent macroscopic orientation is obtained. Diffusion and conductivity measurements of the monomer sample show a large anisotropy of the ion mobility (100 for the cation and 400 for the anion). In the elastomer the anisotropy of the lithium mobility is comparable to that in the monomers.  New mesogenic monomers are designed to incorporate lithium salts into liquid crystalline polymer networks. The low molar mass hostāguest systems exhibit layered structures and a high macroscopic anisotropy of ion mobility. In the first lithium-containing liquid crystalline polymer networks made from these monomers, this behavior is maintained and the macroscopic structure can be permanently fixed.
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Heteroleptic Ruthenium(II) Complex-Containing Polymers and Their Bandgap Tuning and Photosensitizing Properties
AbstractA new synthetic route to novel ruthenium-containing polymers is reported. [Ru(L)(Lā²)Cl2] type complexes (L and Lā² = bidentate N^N ligands) with a dibromo-substituted ligand were polymerized by Stille cross-coupling reaction. The subsequent displacement of chloride ligands by thiocyanate was highly effective and the structures of the target polymers were fully characterized. The main chain absorption showed a significantly red-shift upon metal coordination and the metal-to-ligand charge transfer (MLCT) band of the complex enhanced the photon harvesting ability of the polymer. The extent of Ļ-electron delocalization of the ancillary ligands also showed interesting effects on the electronic properties of the polymers. The photosensitizing and bandgap tuning properties of these Ru(II) complexes demonstrated a new avenue to develop new classes of optoelectronic materials.  Conjugated polymers incorporated with heteroleptic rutheniumcomplexes were synthesized by palladium-catalyzed reaction. The electronic absorption of the polymer main chain was strongly dependent on the ligand on the metal center, which showed a significant red shift compared with the metal-free polymers. The potentials of using these polymers for photosensitizers in organic photovoltaic devices were demonstrated.
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Gelation on Heating of Supercooled Gelatin Solutions
AbstractDiluted (1.0ā1.5 wt%) aqueous gelatin solutions have been cooled to ā10 Ā°C at a cooling rate 20 Ā°C minā1 without freezing and detectable gelation. When heated at a constant heating rate (0.5 ā2 Ā°C minā1), the obtained supercooled solutions demonstrate an atypical process of gelation that has been characterized by regular and stochastically modulated differential scanning calorimetry (DSC) as well as by isoconversional kinetic analysis. The process is detectable as an exothermic peak in the total heat flow of regular DSC and in the nonreversing heat flow of stochastically modulated DSC. Isoconversional kinetic analysis applied to DSC data reveals that the effective activation energy of the process increases from approximately 75 to 200 kJ molā1 as a supercooled solution transforms to gel on continuous h eating.  Aqueous gelatin solutions of low concentration can be cooled to form supercooled solutions without freezing and gelation. When heated at a slow constant heating rate, the supercooled solutions demonstrate an atypical process of gelation that has been characterized by regular and stochastically modulated differential scanning calorimetry as well as by isoconversional kinetic analysis.
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Self-Assembly of Borane End-Functionalized Polystyrene Through Tris(1-pyrazolyl)borate (Tp) Iron(II) Linkages
AbstractTreatment of trimethylsilane-terminated polystyrenes with BBr3 resulted in the formation of dibromoboryl-functionalized mono- or ditelechelic styrene polymers. Subsequently, the borane moieties were selectively converted to tris(1-pyrazolyl)borate (Tp) moieties capable of transition metal coordination. These novel telechelic polymers assemble into redox-active supramolecular polymer structures upon reaction with Fe(II) as indicated by GPC, UVāvis, and cyclic voltammetry studies.  Commonly referred to as āscorpionatesā, poly(1-pyrazolyl)borate (Tp) ligands possess powerful coordination chemistry toward transition metals. In this paper, we introduce a new class of telechelic polymers that are functionalized with Tp ligands and explore their self-assembly into supramolecular structures via coordination to Fe(II). Successful formation of supramolecular polymers was confirmed through NMR, GPC, DSC, CV, and UVāvis analyses.
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Synthesis and Self-Assembly Behavior of OrganicāInorganic Poly(ethylene oxide)-block-Poly(MA POSS)-block-Poly(N-isopropylacrylamide) Triblock Copolymers
AbstractIn this work, the synthesis of 3-methacryloxypropylheptaphenyl POSS, a new POSS macromer (denoted MA-POSS) is reported. The POSS macromer is used to synthesize PEO-b-P(MA-POSS)-b-PNIPAAm triblock copolymers via sequential atom transfer radical polymerization (ATRP). The organic-inorganic, amphiphilic and thermoresponsive ABC triblock copolymers are characterized by means of nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC). Differential scanning calorimetry (DSC) and atomic force microscopy (AFM) show that the hybrid ABC triblock copolymers are microphase-separated in bulk. Cloud point measurements show that the effect of the hydrophiphilic block (i.e. PEO) on the LCSTs is more pronounced than the hydrophobic block (i.e. P(MA-POSS)). Both transmission electron microscopy (TEM) and dynamic light scattering (DLS) show that all the triblock copolymers can be self-organized into micellar aggregates in aqueous solutions. The sizes of the micellar aggregates can be modulated by changing the temperature. The temperature-tunable self-assembly behavior is interpreted using a combination of the highly hydrophobicity of P(MA-POSS), the water-solubility of PEO and the thermoresponsive property of PNIPAAm in the triblock copolymers.  A series of organic-inorganic triblock copolymers composed of poly(ethylene oxide) (PEO) and poly(N -isopropylacrylamide) (PNIPAAm) endblocks and a poly(MA POSS) midblock are synthesized via a sequential atom transfer radical polymerization (ATRP) approach. The PEO-b-P(MA POSS)-b-PNIPAAm ABC triblock copolymers possess microphase-separated morphologies. It is found that, in aqueous solutions, the ABC triblock copolymers can display a temperature-tunable self-assembly behavior.
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Proton-Conducting Poly(phenylene oxide)āPoly(vinyl benzyl phosphonic acid) Block Copolymers via Atom Transfer Radical Polymerization
AbstractBlock copolymers containing poly(phenylene oxide) (PPO) and poly(vinyl benzyl phosphonic acid) segments are synthesized via atom transfer radical polymerization (ATRP). Monofunctional PPO blocks are converted into ATRP active macroinitiators, which are then used to polymerize a diethyl p-vinylbenzyl phosphonate monomer in order to obtain phosphonated block copolymers bearing pendent phosphonic ester groups. Poly(phenylene oxide-b-vinyl benzyl phosphonic ester) block copolymers are hydrolyzed to corresponding acid derivatives to investigate their proton conductivity. The effect of the relative humidity (RH) is investigated. The proton conductivity at 50% RH and one bar of vapor pressure approaches 0.01 S cmā1.  A new type of amphiphilic blockcopolymer based on PPO and vinylbenzylphosphonic acid is synthesized via a combination of ATRP and polycondensation. The polymers show excellent proton conductivity in combination with morphology control due to the block structure.
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UCST Behavior of Cyclodextrin-Containing Poly(Pseudo-Betaines) Based on Supramolecular Structures
AbstractA novel monofunctional Ī²-cyclodextrin monomer is synthesized via copper(I)-catalyzed azide/alkyne click reaction. By free radical polymerization, cyclodextrin-containing polyelectrolytes can be obtained as an intriguing polymeric host for smart supramolecular assembling systems. By inclusion complexation of adamantyl carboxylate as a model guest, pseudo-betaine structures with reversible UCST behavior are obtained. Furthermore, the complex stability constants are determined by isothermal titration calorimetry at different temperatures.  The synthesis and polymerization of a novel monofunctional Ī²-cyclodextrin monomer are described. Furthermore, the properties and the ability to form pseudo-betaine structures due to supramolecular host/guest interactions are investigated.
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Preparation of Responsive Micrometer-Sized Microgel Particles with a Highly Functionalized Shell
AbstractWe describe a facile approach for the synthesis of micrometer-sized (ā¼3.5 Ī¼m), pH-responsive microgel particles, which have functional carboxylic acid groups concentrated in the shell. The large size offers the possibility to directly study the interactions between individual, isolated microgel particles with active ingredients by optical microscopy. Our results show that the synthesized microgel particles can load and release active ingredients via changing pH values. The complexation of Ca2+ with the -COOH functional groups located at the microgel surfaces not only regulates the active ingredient's uptake efficiency, but also provides a novel way to reveal the spatial distribution of the functional groups inside the microgel particles.  A facile method is reported for the preparation ofuniform-sized multi-responsive microgel particles which have a highly functionalized shell and show the ability to load active ingredients as well as release them through pH changes or added calcium ions.
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Patterned Immobilization of a Luminescent Ru(II) Complex in Polymer Films Using the Photoreaction of Benzyl thiocyanate: Toward Color Emission Tuning of Electroluminescent Devices
AbstractThis contribution deals with the patterned immobilization of a highly luminescent Ru(II) complex in thin polymer films. Photosensitive polymers bearing benzyl thiocyanate groups in the side chain undergo a photoisomerization reaction upon irradiation with UV light. This photoreaction leads to the formation of isothiocyanate groups, which readily react with primary amino groups. We report on the immobilization of a highly luminescent Ru(II) complex in the illuminated areas of a norbornene based polymer by means of this photoreaction. In combination with lithographic techniques, patterned, luminescent polymer films are realized. A novel approach for tuning the electroluminescence of polyfluorene-based organic light- emitting diodes by the immobilization of this Ru(II) complex in the emission layer is suggested.  A straightforward approach for the patterned immobilization of a highly luminescent Ru(II) complex in thin polymer films is described. Exploiting this technique the Ru(II) complex can also be immobilized in the emission layer of polyfluorene-based OLEDs, which paves the way toward tuning of the electroluminescence.
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Low-Power Upconversion in Dye-Doped Polymer Nanoparticles
AbstractExamples of nanoscale low-power upconverting systems are rapidly increasing because of their potential application in numerous areas such as bioimaging or drug delivery. The fabrication of dye-doped cross-linked rubbery nanoparticles that exhibit upconversion even at relatively low power densities is reported here. The nanoparticles were prepared by surfactant-free emulsion polymerization of n-butylacrylate with divinylbenzene as a cross-linker, followed by dyeing of the resulting particles with a two-chromophore system composed of a palladium porphyrin sensitizer, and diphenylanthracene. Blue emission (ā440 nm) of these systems was observed upon excitation at 532 nm. In addition to their optical properties, the particles were characterized by electron microscopy and dynamic light scattering.  The fabrication of dye-doped cross-linked rubbery nanoparticles that exhibit upconversion even at relatively low power densities is reported here. Successful loading of an upconverting dye pair into the nanoparticles following surfactant-free emulsion polymerization are reported. In addition to optical properties, the nanoparticles were characterized by electron microscopy and dynamic light scattering.
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Transformation of Regioregular Organotitanium Polymers into Group 16 Heterole-Containing Ļ-Conjugated Materials
AbstractRegioregular organometallic polymers with titanacyclopentadiene units, obtained from terminal diynes and a low-valent titanium complex, were subjected to reactions with disulfur dichloride and selenium (I) chloride to give Ļ-conjugated polymers with thiophene and selenophene units in the main chain in 63% and 86% yields. Their number-average molecular weights were estimated as 4300 and 5700, respectively. Both polymers were found to be fully Ļ-conjugated and their HOMO energy levels were remarkably high (ā5.3 eV and ā5.0 eV for thiophene- and selenophene-containing polymers, respectively) as supported by their UV-vis absorption spectra and CV analyses.  Reactions of regioregular organometallic polymers possessing titanacyclopentadiene-2,5-diyl units to give polymers containing thiophene or selenophene units are described. The transformation of the main chain structure of the organotitanium polymer takes place smoothly by reactions with S2Cl2 or Se2Cl2 to give fully Ļ-conjugated polymers with high HOMO energy levels.
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Controlled Radical Polymerization Mediated by AmineāBis(phenolate) Iron(III) Complexes
AbstractTetradentate amineābis(phenolate) iron(III) halide complexes containing chloro substituents on the aromatic ring are extremely efficient catalysts for controlled radical polymerization. Molecular weights are in good agreement with theoretical values and polydispersity indexes (PDIs) are as low as 1.11 for styrene and methyl methacrylate polymerizations. Complexes containing alkyl substituents on the aromatic ring are less efficient. Kinetic data reveal activity for styrene polymerization among the fastest reported to date and initial studies implicate a multimechanism system. Despite the highly colored polymerization media, simple work-up procedures yield pure white polymers.  Facile recovery of white polymers is essential for the commercialization of controlled radical polymerization. A new family of highly active, benign iron catalysts, believed to operate through a unique dual-control mechanism, is reported. Despite the deep purple color of the complexes and polymerization media, simple precipitation yields pure white polymers with polydispersities as low as 1.1.
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Luminescent and Light Refractive Polymers: Synthesis and Optical and Photonic Properties of Poly(arylene ethynylene)s Carrying Silole and Tetraphenylethene Luminogenic Units
AbstractA facile route for the synthesis of luminescent and light refractive polymers is proposed. Silole-containing diyne and halogenated tetraphenylethene derivatives are synthesized and their coupling reactions furnish poly(arylene ethynylene)s with high molecular weights in high yields. All of the polymers are soluble and film-forming and possess a high thermal stability. They emit strong green lights when their solutions and nanoparticle suspensions are photoexcited. The polymers show high refractive indices with low chromatic dispersions. Their RI values can be modulated and their thin films can be crosslinked using UV irradiation, generating negative photoresist patterns.  Soluble, high molecular weight poly(arylene ethynylene)s are constructed in high yields from silole and tetraphenylethene building blocks. The polymers are thermally stable and light emissive. They exhibit high refractive indices and can generate negative photoresist patterns upon UV irradiation.
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Divergent Synthesis of Ruthenium Alkynyl Dendrimers and a Two-Photon Absorption Cross-Section Dendritic Effect
AbstractRuthenium alkynyl dendrimers up to second generation in size have been prepared by a divergent route and exploiting Sonogashira coupling. The cubic NLO properties have been examined by wide spectral range fs Z-scan studies, revealing an NLO dendritic effect. The significant increase in NLO properties seen on generation increase is maintained when the coefficients are scaled by the number of metal atoms, the dendrimer molecular weights, or the number of āeffectiveā (delocalizable Ļ) electrons in the dendritic structures.  Ruthenium alkynyl dendrimers incorporating 1,2-bis(diphenylphosphino)ethane co-ligands have been synthesized in a divergent manner, utilizing Pd-catalyzed coupling at organometallic fragments. These compounds display an NLO dendrimer effect ā their cubic nonlinearities and two-photon absorption cross-sections increase nonlinearly on increasing dendrimer generation.
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Inkjet Printing of Zinc(II) Bis-2,2ā²:6ā²,2ā³-Terpyridine Metallopolymers: Printability and Film-Forming Studies by a Combinatorial Thin-Film Library Approach
AbstractFor the first time, thin-film libraries of zinc(II) bis-2,2ā²:6ā²,2ā³-terpyridine metallopolymers are prepared by inkjet printing to study structureāproperty relationships and their possible usage for organic photovoltaic (OPV) or polymer light-emitting diode (PLED) applications. By using a combinatorial approach, various important parameters, including solvent system, dot spacing, and substrate temperature, as well as UV-vis absorption and emission properties, are screened in a materials efficient and reproducible manner. Homogeneous films with a thickness of 150 ā200 nm were obtained when printed at 40 ā50 Ā°C and from a solvent mixture of N,N-dimethylformamide and acetophenone in a ratio of 90/10. In applications such as OPV and PLEDs the control over film thickness and homogeneity are central to obtain good device properties.  Thin-film libraries of zinc(II) bis-2,2ā²:6ā²,2ā³- terpyridine metallopolymers were prepared by inkjet printing to study structureāproperty relationships between the synthesized polymers and their possible usage for organic photovoltaic (OPV) or polymer light-emitting diode (PLED) applications. Several processing parameters, including dot spacing, solvent system, substrate temperature, and UV-vis absorption/emission, were studied, for the first time, in a combinatorial approach using inkjet printing.
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Block Copolypeptides Prepared by N-Carboxyanhydride Ring-Opening Polymerization
AbstractN-Carboxyanhydride ring-opening polymerization (NCA ROP) is a synthetically straightforward methodology to generate homopolypeptides. Extensive control over the polymerization permits the production of highly monodisperse synthetic polypeptides to a targeted molecular weight in the absence of unfavorable side reactions. Sequential NCA ROP permits the creation of block copolypeptides composed of individual polypeptide blocks boasting different functionalities, secondary structures, and desirable chemical properties. Consequently, a plethora of novel materials have been generated that have found wide-range applicability. This review offers an insight into contemporary synthetic approaches toward NCA ROP before highlighting a number of block copolypeptide architectures generated.  N-Carboxyanhydride ring-opening polymerization enables the controlled generation of numerous distinctive block copolypeptides possessing potential biomedical applicability. Such structures may offer biocompatibility in addition to stimuli-responsive and self-assembly properties. This review presents the synthetic methodologies employed and applications found for a range of block polypeptides produced of late.
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Poly(Ļµ-caprolactone) Decorated With One Room-Temperature Red-Emitting Ruthenium(II) Complex: Synthesis, Characterization, Thermal and Optical Properties
AbstractThe incorporation of room-temperature red-emissive [RuII(dqp)(dqp-CH2OH)]2+ (dqp is 2,6-di(quinolin-8-yl)pyridine) in poly(Ļµ-caprolactone) (PCL) is explored following two routes. First, the ring-opening polymerization of Ļµ-caprolactone is investigated using the free ligand and the complex as initiators. Alternatively, the complexation strategy utilizing PCL-dqp as a macroligand is detailed. Both routes yield room-temperature emissive polymers centered at 400 nm (free ligand) and 680 nm (complex) in aerated solvent. DSC and TGA showed the typical properties of PCL, for example, the melting point (59 Ā°C).  An efficient assembly strategy of light-active complexes into polymersis essential for future energy conversion materials. The scope of positional control of suitable metal complexes is investigated by functional initiators and post-modification of poly(Ļµ-caprolactone). The prepared dye-labeled polymers display blue or red emission at ambient conditions.
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Synthesis and Photovoltaic Properties of 1,8-Carbazole-Based DonorāAcceptor Type Conjugated Polymers
Abstract1,8-Diethynylcarbazole-based conjugated polymers were synthesized by the acetylenic oxidative coupling reaction or Pd-catalyzed Sonogashira reaction of the newly designed 3,6-dialkylated 1,8-diethynylcarbazole monomers. In particular, the Sonogashira polycondensation was effective for the preparation of donorāacceptor type alternating copolymers. The UV-vis absorption and fluorescence spectra of the polymers revealed the strength of the donorāacceptor interactions as well as their self-assembling features. The combination of electrochemical redox potentials and optical band gaps enabled the estimation of the polymer energy levels. The bulk-heterojunction solar cells composed of these promising polymers and PCBM exhibited a photoconversion efficiency (PCE) of 0.24%. It was determined that the partial doping of the bulk-heterojunction layer increased the open-circuit voltage (Voc), but decreased the short-circuit current (Jsc).  The photovoltaic properties of 1,8-carbazole-based donorāacceptor type copolymers are for the first time reported. The introduction of n-alkane substituents into the 3,6-positions on the carbazole allows good self-aggregation even in solutions. Bulk-heterojunction solar cell studies suggest the importance of comonomer structures to optimize the photovoltaic performances.
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Improving Hydrogen Adsorption Enthalpy Through Coordinatively Unsaturated Cobalt in Porous Polymers
AbstractThe design and synthesis of a new porous organic polymer (POP) incorporated with cobalt carbonyl complexes through built-in bipyridinic coordination sites for hydrogen storage are described. A thermal activation process was developed to remove the ligated carbonyl and carbon dioxide in order to expose the cobalt atomically inside of porous structure. Various spectroscopic and physical characterization techniques were used to study the coordinated Co sites and the POP's surface property. Upon thermal activation, this new cobalt-containing POP showed improved hydrogen uptake capacity and isosteric heat of adsorption.  A porous organic polymer functionalized with bipyridineācobalt complexes is prepared through copolymerization of a spirobifluorene and a bipyridine monomers using cobalt carbonyl as catalysts and coordination agent. Hydrogen adsorption enthalpy increases by over 30% upon removal of the carbonyl ligand and CO2 from the porous network by a simple thermal treatment
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Metallo-Supramolecular Materials Based on Amine-Grafting Onto Polypentafluorostyrene
AbstractThe post-modification of polypentafluorostyrene via the selective substitution of the para- fluorine by amine-functionalized molecules represents a versatile method for the preparation of functional materials. This communication presents the extension of this synthetic approach towards metallosupramolecular materials. First, the incorporation of terpyridines as metallo-supramolecular binding motifs is demonstrated, which enables the formation of a supramolecular crosslinked gel upon the addition of Fe(II) ions. Second, the linkage of phosphorescent iridium(III) complexes is reported yielding a copolymer that combines the excellent photophysical properties of the iridium(III) complex and the good solubility and processability of the polymer.  The post-modification reaction of poly(pentafluorostyrene) allows the effective grafting of supramolecular binding motifsonto the linear polymer backbone. A metallo-supramolecular gel was obtained after the addition of iron ions as well as a phoshorescent iridium-containing polymer by grafting amine-functionalized metal complexes to the polymer.
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Facile Preparation of a Fully Ļ-Conjugated Metallopolymer Composed of Fused Salphen Complexes
AbstractNovel Ļ-conjugated compounds composed of fused salphen groups as a repeating unit, embedded with four or an indefinite number of zinc nuclei have been synthesized. The solid-state absorption spectra, IR spectra, and powder XRD patterns of these compounds are investigated and compared with those of analogous oligomers. The presumptive polymer contains at least five units of the salphen complex and its assembly is highly ordered in the solid state.  A macromolecule composed of an indefinite number of Zn-salphen complexes fused into a unique conjugated system is synthesized. The repeating molecular structure is spectroscopically examined by comparison with its analogous oligomers, including a newly synthesized tetranuclear complex. The XRD pattern suggests that the molecular assembly is highly ordered in the solid state by virtue of various intermolecular interactions.
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Morphology Tailoring of Thin Film Block Copolymers on Patterned Substrates
AbstractIt is well known that chemically patterned substrates can direct the assembly of adsorbed layers or thin films of block copolymers. For a cylinder-forming diblock copolymer on periodically spot-patterned substrates, the morphology of the block copolymer follows the pattern at the substrate; however, with different periodic spacing and spot size of the pattern, novel morphologies can be created. Specifically, we have demonstrated that new morphologies that are absent in the bulk system can be tailored by judiciously varying the mismatch between the width of the pattern and the periodic spacing of the bulk block copolymer, the top surface affinity, and spot size. New morphologies can thus be achieved, such as honeycomb and ring structures, which do not appear in the bulk system. These results demonstrate a promising strategy for fabrication of new nanostructures from chemically patterned substrates.  By judiciously varying the mismatch between the spacing of the pattern and the bulk periodic spacing of the cylinder-forming block copolymer, the top surface affinity, and spot size, new morphologies can be achieved, such as honeycomb and ring structures, which do not appear in the bulk system.
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The Naked-Eye Detection of NH3āHCl by Polyaniline-Infiltrated TiO2 Inverse Opal Photonic Crystals
AbstractA reversible color change of a polyaniline-infiltrated TiO2 inverse opal photonic crystal (PC) film can be obtained when the PC is switched from an acidic to alkali vapor environment. In a saturated NH3 environment, the stopband of the as-prepared PCs changes from 556 to 688 nm; such large shift of 132 nm could be observed, corresponding to a clear color change from green to red. After placing in HCl vapor, the stopband undergoes a blue-shift and the color turns back to green. The result is ascribed to PANI being doped or dedoped by acid or base and the effective refractive index of the PC film varying accordingly. The naked-eye detection of NH3 and HCl vapors can be realized by the reversible color change of the PC film, which is of importance for chemical and biological sensors.  A reversible color change of a polyaniline-infiltrated TiO2 inverse opal photonic crystal (PC) film can be obtained when the PC is switched from an NH3 to HCl vapor environment. The naked-eye detection of NH3 and HCl vapors can be realized by a reversible color change of the PC film, which is very important for chemical and biological sensors.
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Perfluorophenyl-Terpyridine Ruthenium Complex as Monomer for Fast, Efficient, and Mild Metallopolymerizations
AbstractHerein, the new concept of thiol-para-fluorine āclickā chemistry is employed for the formation of ruthenium(II) bisterpyridine metallopolymers in a fast and efficient manner. In general, the assembly of comparable metallopolymers requires high temperatures and long reaction times. In contrast to established methods, when utilizing a pentafluorophenyl-substituted homoleptic RuIIbisterpyridine complex, as a monomer, thiol-functionalized organic spacer units can easily be introduced at low temperatures and in very short reaction times. Furthermore, alternating arrangements of different metal ions (e.g., RuII and FeII) in metallopolymers can be achieved.  A new, fast, and efficient methodfor the synthesis of ruthenium(II) bis terpyridine metallopolymers is presented. The homoleptic RuII complex of 4ā²-(perfluorophenyl)-2,2ā²:6ā²,2ā³-terpyridine is a versatile monomer for a thiol -para- fluorine click reaction and can easily be converted with Ļ-conjugated dithiols resulting in metallopolymers in a fast and efficient manner.
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Synthesis of Ļ-Conjugated Polymers Containing Aminoquinoline-Borafluorene Complexes in the Main-Chain
AbstractThe regulation of electron transfer between a conjugated polymer and ligands orthogonally connected to the main-chain is reported. Poly(arylene-ethynylene)s containing aminoquinoline-borafluorene complexes in the main-chain are synthesized in good yields by a SonogashiraāHagihara coupling. Single crystal X-ray analysis of a model compound has elucidated the complex's structure in which the aminoquinolate moiety and the borafluorene ring are connected directly and orthogonally. Moreover, the optical properties of the polymers are characterized by UV-vis absorption and photoluminescence spectra. Perfluorinated alkyl chain-containing polymers show strong emission, while hydrocarbon chain-containing ones exhibit only a slight emission. DFT calculation suggests that an electron transfer from the excited main-chain to the aminoquinolate ligand is suppressed because of the lowered LUMO level by introducing the electron withdrawing groups, resulting in the significant emission.  An aminoquinoline-borafluorene complex is successfully incorporated into a main-chain of poly(arylene-ethynylene)s. This moiety restricts two aromatic planes, aminoquinoline and borafluorene, orthogonally, and extends the Ļ-conjugation of the main-chain. The aminoquinolate moiety acts as a moderate electron acceptor so that the side-chains of the polymers regulate the fluorescence quantum yields by electron transfer.
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A Simple and Effective Approach to Vesicles and Large Compound Vesicles via Complexation of Amphiphilic Block Copolymer With Polyelectrolyte in Water
AbstractThis work reports for the first time a simple and effective approach to trigger a spheres-to- vesicles morphological transition from amphiphilic block copolymer/polyelectrolyte complexes in aqueous solution. Vesicles and large compound vesicles (LCVs) were prepared via complexation of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) with poly(acrylic acid) (PAA) in water and directly visualized using cryo-TEM. The complexation and morphological transitions were driven by the hydrogen bonding between the complementary binding sites on the PAA and PEO blocks of the block copolymer. The findings in this work suggest that complexation between amphiphilic block copolymer and polyelectrolyte is a viable approach to vesicles and LCVs in aqueous media.  A simple, effective approach to trigger a spheres-to-vesicles morphological transition from amphiphilic block copolymer/polyelectrolyte complexes in aqueous solution is reported. Vesicles and large compound vesicles are prepared via complexation of polystyrene-block-poly(ethylene oxide) with poly(acrylic acid) in water and directly are visualized using cryo-TEM.
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Poly(disubstituted acetylene)s With Pendant Naphthalimide-Based Fluorophore Groups
AbstractNew stable polyacetylenes whose quantum yield of fluorescence is increased up to 62% because of the presence of pendant 4-(piperidine-1-yl)-1,8-naphtalimide groups are described. The polymers are prepared by two-step modification of copolymers of 1-(4-tert-butylphenyl)-6-chlorohex-1-yne and 1-phenylhex-1-yne consisting of the exchange of chlorine atoms at side groups for azide groups and subsequent Huisgen click reaction of the azide groups with ethynyl groups of N-(prop-1-yne-3-yl)-4-(piperidine-1-yl)-1,8-naphthalimide. Modification is evidenced by 1H NMR, IR, Raman and UVāvis spectroscopy. Modified polymers show the excitation energy transfer from their main chains on fluorophores and nearly preservation of fluorescence properties of fluorophores upon their binding to polymer chains.  Environmentally stable poly(disubstituted acetylene)s with a quantum yield of fluorescence that is is increased up to 62% because of the presence of 4-(piperidine-1-yl)-1,8-naphtalimide fluorophores in the side groups are described. Two-step modification of a primary polymer is presented as an effective strategy for the preparation of functional polyacetylenes.
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Micropatterns of Non-Circular Droplets of Nanostructured PS-b-PEO Copolymer by Solvent-Assisted Wetting on a Chemically Periodic Surface
AbstractA method to fabricate micropatterns of non-circular droplets of a self-assembled block copolymer by solvent-assisted wetting on chemically periodic surface is presented. The block copolymer is dewetted on a topographic pre-pattern to form an array of microdroplets with a sphere-capped shape and circular contact line. The droplets are then transferred onto a chemically periodic Au line pattern microcontact-printed with two types of self-assembled monolayers (SAMs). Solvent vapor application provides sufficient mobility to the block copolymer molecules to induce spreading of the transferred droplets, resulting in two types of non-circular microdroplet growth. The growth behavior depends on the size of initial droplets relative to periodic line width and on the initial registries of as-transferred droplets.  Arrays of sphere-capped microdroplets of a PS-b-PEO block copolymer are transferred from a PDMS mold to SAM-treated Au substrates containing periodic hydrophilic and hydrophobic lines, followed by the solvent annealing. This gives rise to a micropattern of non-circular droplets of the copolymer with hierarchically ordered self-assembled block copolymer nanostructures.
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Synthesis of Hyperbranched Polyethylene Amphiphiles by Chain Walking Polymerization in Tandem with RAFT Polymerization and Supramolecular Self-Assembly Vesicles
AbstractA novel polymerization methodology for efficient synthesis of hyperbranched polyethylene amphiphiles by chain walking polymerization (CWP) followed by RAFT polymerization has been developed. Hyperbranched polyethylene with hydroxyl ends (HBPE-OHs) is first synthesized via chain walking copolymerization of ethylene with 2-hydroxyethyl acrylate with Pd-Ī±-diimine catalyst. The hydroxyl groups of hyperbranched polyethylene are then converted into thiocarbonyl thio moieties by an esterification reaction with trithiocarbonate 3-benzylsulfanylthiocarbonyl sulfanylpropionic acid (BSPA). The hyperbranched polyethylene with thiocarbonyl thio moiety ends (HBPE-BSPAs) is used as a macro-RAFT agent for the synthesis of hyperbranched polyethylene amphiphiles, HBPE-PDMAEMAs, by RAFT polymerization of N,N-dimethylaminoethyl methacrylate (DMAEMA). The resultant HBPE-PDMAEMAs can self-assemble to form supramolecular polymer vesicles in aqueous solution. A preliminary investigation on thermo- and pH-responsive behaviors of the polymer is also reported.  A novel polymerization methodology, chain walking polymerization (CWP) followed by reversible addition fragmentation transfer (RAFT) polymerization, has been developed for efficient synthesis of hyperbranched polyethylene amphiphiles (HBPE-PDMAEMAs). The hyperbranched polyethylene amphiphiles can self-assemble into supramolecular polymer vesicles in aqueous solution. These hyperbranched polyolefin vesicles may be potentially useful in nanobiotechnology applications.
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A Novel Thermotropic Elastomer based on Highly-filled LDH-SSB Composites
AbstractElastomeric composites are prepared based on solution styrene butadiene elastomer and zinc-aluminium layered double hydroxides (LDH), using a conventional sulphur cure system. Up to 100 parts per hundred rubber of LDH are incorporated into the elastomer matrix. The composites exhibit an interesting phenomenon of thermoreversible transparency, i.e. the transparent sample becomes opaque at warm condition and restores the transparency at room temperature. The transparency is found to be increased as the amount of LDH was increased. The addition of LDH gradually improved the mechanical, dynamic mechanical performance and thermal stability of the base elastomer. These developped elastomers could be utilised as smart materials in different applications.  Thermotropic elastomeric composites are prepared based on solution styrene butadiene copolymer and zinc-aluminium layered double hydroxides, using a conventional sulphur curing system. The material develops great contact clarity at room temperature, but becomes totally opaque upon warming.
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Annealing Effect on Electrospun Polymer Fibers and Their Transformation into Polymer Microspheres
AbstractElectrospinning is a simple and convenient technique to produce polymer fibers with diameters ranging from several nanometers to a few micrometers. Different types of polymer fibers have been prepared by electrospinning for various applications. Among different post-treatment methods of electrospun polymer fibers, the annealing process plays a critical role in controlling the fiber properties. The morphology changes of electrospun polymer fibers under annealing, however, have been little studied. Here we investigate the annealing effect of electrospun poly(methyl methacrylate) (PMMA) fibers and their transformation into PMMA microspheres. PMMA fibers with an average size of 2.39 Ī¼m are first prepared by electrospinning a 35 wt% PMMA solution in dimethylformamide. After the electrospun fibers are thermally annealed in ethylene glycol, a non-solvent for PMMA, the surfaces of the fibers undulate and transform into microspheres driven by the Rayleigh instability. The driving force of the transformation process is the minimization of the interfacial energy between the polymer fibers and ethylene glycol. The sizes of the microspheres fit well with the theoretical predictions. Longer annealing times are found to be required at lower temperatures to obtain the microspheres.  The annealing effect of electrospun poly(methyl methacrylate) (PMMA) fibers and their transformation into microspheres are investigated. The PMMA fibers with an average size of 2.39 Ī¼m are first prepared by electrospinning a 35 wt% PMMA solution in DMF. After the electrospun fibers are thermally annealed in ethylene glycol, a non-solvent for PMMA, the surfaces of the fibers undulate and transform into microspheres driven by the Rayleigh instability.
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Synthesis of Graft Copolymers Based on Poly(2-Methoxyethyl Acrylate) and Investigation of the Associated Water Structure
AbstractGraft copolymers composed of poly(2-methoxyethyl acrylate) are prepared employing controlled radical polymerization techniques. Linear backbones bearing atom transfer radical polymerization (ATRP) initiating sites are obtained by reversible additionāfragmentation chain transfer copolymerization of 2-methoxyethyl acrylate (MEA) and 2-(bromoisobutyryloxy)ethyl methacrylate (BriBuEMA) as well as 2-hydroxyethyl methacrylate and BriBuEMA in a controlled manner . MEA is then grafted from the linear macroinitiators by Cu (I)-mediated ATRP. Fairly high molecular weights (>120 000 Da) and low polydispersity indices (1.17ā1.38) are attained. Thermal investigations of the graft copolymers indicate the presence of the freezing bound water, and imply that the materials may exhibit blood compatibility.  Graft copolymers featuring poly(2-Methoxyethyl Acrylate) grafts are constructed by controlled radical polymerization methods. While reversible additionāfragmentation chain transfer polymerization is employed to build the linear backbones, atom transfer radical polymerization is utilized to attain the target architecture taking the āgrafting fromā approach. The associated water structure, which provides hints about the materials' blood compatibility, is investigated by differential scanning calorimetry.
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Facile Synthesis of Supramolecular Ionic Polymers That Combine Unique Rheological, Ionic Conductivity, and Self-Healing Properties
AbstractA new family of supramolecular ionic polymers is synthesized by a simple method using (di-/tri-)carboxylic acids and (di-/tri-)alkyl amines. These polymers are formed by carboxylate and ammonium molecules that are weakly bonded together by a combination of ionic and hydrogen bonds, becoming solid at room temperature. The supramolecular ionic polymers show a sharp rheological transition from a viscoelastic gel to a viscous liquid between 30 and 80 Ā°C. This sharp viscosity decrease is responsible for an unprecedented jump in ionic conductivity of four orders of magnitude in that temperature range. As a potential application, this chemistry can be used to develop polymeric materials with self-healing properties, since it combines properties from supramolecular polymers and ionomers into the same material.  A new family of supramolecular ionic polymers is synthesized by a method using (di-/tri-)carboxylic acids and (di-/tri-)alkyl amines. Supramolecular ionic polymers combine unique rheological properties, such as a sharp transition between a viscoelastic gel and viscous liquid, with an unprecedented relationship between ionic conductivity and temperature. This can be used to develop polymeric materials with self-healing properties and ionic conductivity.
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Water-developable Poly(2-oxazoline)-Based Negative Photoresists
AbstractCopoly(2-oxazoline)-based photoresists are prepared from pEtOx80Bu=Ox20 and pPhOx80Dc=Ox20, respectively, a tetrathiol, and a photosensitive initiator. It is possible to prepare copoly(2-oxazoline)s bearing unsaturated side chains in a microwave reactor on a decagram scale in reaction times of 100 min or shorter. UV irradiation of dried polymer films through a quartz mask induces the thiol-ene reaction in the illuminated areas. Subsequent development of the polymer films in halogen-free solvents reproduces the negative pattern of the mask with a resolution of 2 Ī¼m. The pEtOx80Bu=Ox20-derived photoresists can also be developed in water.  Copoly(2-oxazoline)s bearing unsaturated side chains can be used for the formulation of negative photoresists, crosslinking of which is achieved by the functional principle of UV-induced thiol-ene reactions. These photoresists adhere to various substrates commonly used in printed circuit board industries. After illumination through a quartz mask and subsequent development in halogen-free solvents, these photoresists exhibit resolution in the 2 Ī¼m range.
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Synthesis and Polymerization of Fused-Ring Thienodipyrrole Monomers
AbstractThe synthesis and polymerization of fused-ring 1,7-didodecyl-1,7-dihydrothieno[3,2-b:4,5-bā²]dipyrrole monomer are reported. The FeCl3-mediated oxidative polymerization and Stille coupling polymerization of the thienodipyrrole monomer were employed to generate homopolymers and an alternating copolymer with thiophene. The synthesized polymers have molecular weights ranging from 1600 to 6500 g molā1 and display the absorption maxima at ā355 nm.  The synthesis of 1,7-didodecyl-1,7-dihydrothieno[3,2-b:4,5-bā²]dipyrrole monomer and its polymerization are reported for the first time. The FeCl3-mediated oxidative polymerization and Stille coupling polymerization of the thienodipyrrole monomer are employed to generate homopolymers and an alternating copolymer with thiophene.
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Fabrication of Chitosan Single-Component Microcapsules With a Micrometer-Thick and Layered Wall Structure by Stepwise Core-Mediated Precipitation
AbstractIncubation of CaCO3 microparticles in chitosan (CS) solution at pH 5.2 and following with ethylenediaminetetraacetic acid disodium salt (EDTA) treatment resulted in CS single-component microcapsules with an ultra-thick wall structure. Repeating the incubation caused stepwise increase of wall thickness and finally resulted in CS microcapsules with a layered structure. This unique method is mediated by precipitation of CS on the CaCO3 particles as a result of pH increase caused by the partial dissolution of CaCO3. The obtained CS capsules are stable at neutral pH.  Chitosan (CS) single-component microcapsules with a micron-thick and layered wall structure were fabricated by a stepwise core-mediated precipitation. With the ease of fabrication, the micron-size wall, and the capability of encoding, the CS microcapsules are expected to find applications in areas of drug delivery, biosensors, as well as diagnosis.
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Novel Source of Trifluoromethyl Radical As Efficient Initiator for the Polymerization of Vinylidene Fluoride
AbstractA persistent perfluoroalkyl radical (PPFR), perfluoro-3-ethyl-2,4-dimethyl-3-pentyl, is shown to be a good source of ā¢CF3 radicals and a useful radical capable of initiating the polymerization of vinylidene fluoride (VDF). NMR characterizations of the resulting PVDF homopolymers showed that polymerization of VDF was exclusively initiated by ā¢CF3 radicals. The addition of ā¢CF3 radical onto VDF was regioselective leading to CF3-CH2-CF2-PVDF and the CF3 end-group acted as an efficient label to assess the molecular weights by 19F NMR spectroscopy. Various [PPFR]0/[VDF]0 initial molar ratios lead to CF3āPVDFāCF3 of different molecular weights. When that ratio decreased, both the molecular weights and the thermostability of these PVDFs increased, showing less defects of chaining and higher crystallinity.  Perfluoro-3-ethyl-2,4-dimethyl-3-pentylis a persistent radical that can generate ā¢CF3 radicals. This feature was used to initiate the polymerization of vinylidene fluoride. The generated PVDF chains were exclusively functionalized by CF3 end-groups, indicating that only the ā¢CF3 radicals could initiate the polymerization. Thermal analyses showed both a good thermostability and high crystallinity, indicating lower proportion of chain defects
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Microwave-Assisted Hydrogel Synthesis: A New Method for Crosslinking Polymers in Aqueous Solutions
AbstractIt has been found that hydrogels may be formed by microwave irradiation of aqueous solutions containing appropriate combinations of polymers. This new method of hydrogel synthesis yields sterile hydrogels without the use of monomers, eliminating the need for the removal of unreacted species from the final product. Results for two particularly successful combinations, poly(vinyl alcohol) with either poly(acrylic acid) or poly(methylvinylether-alt-maleic anhydride), are presented. Irradiation using temperatures of 100ā150 Ā°C was found to yield hydrogels with large equilibrium swelling degrees of 500ā1000 g gā1. Material leached from both types of hydrogel shows little cytotoxicity towards HT29 cells.  Hydrogels can be synthesised by the microwave irradiation of an appropriate combination of polymers in aqueous solution. This new method of crosslinking yields sterile hydrogels in a one-pot synthesis without the need for further processing and could potentially be applied to a wide range of polymers, resulting in new materials.
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Cobaltocenium-Containing Block Copolymers: Ring-Opening Metathesis Polymerization, Self-Assembly and Precursors for Template Synthesis of Inorganic Nanoparticles
AbstractSide-chain cobaltocenium-containing block copolymers are prepared by ring-opening metathesis polymerization (ROMP). These block copolymers include one cobaltocenium-containing block, with the second block being either a nonmetal-containing segment or a cobaltocenium-containing segment with different counterions. These block copolymers are self-assembled into spherical core/shell micelles in solutions. A template strategy is used to prepare cobalt (II or III)-containing nanoparticles by treating the self-assembled micelles via UV/ozonolysis and pyrolysis. Characterization by X-ray photon spectroscopy and X-ray diffraction indicates that these nanoparticles consist of different oxidants of cobalt, depending on the chemical compositions of block copolymers.  Cationic cobaltocenium-containing block copolymers are prepared by ring-opening metathesis polymerization. These block copolymers exhibit counterion-dependent self-assembly in solutions. The stability of the self-assembled micelles is dictated by ion exchange between the two different segments. These micelles are further used as templates to prepare oxidized cobalt nanoparticles, which show a magnetic response.
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Photonics of a Conjugated Organometallic PtāIr Polymer and Its Model Compounds Exhibiting Hybrid CT Excited States
AbstractTrans- dichlorobis(tri-n-butylphosphine)platinum(II) reacts with bis(2- phenylpyridinato)-(5,5ā²-diethynyl-2,2ā²-bipyridine)iridium(III) hexafluorophosphate to form the luminescent conjugated polymer poly[trans-[(5,5ā²-ethynyl-2,2ā²-bipyridine)bis(2- phenylpyridinato)-iridium(III)]bis(tri-n-butylphosphine)platinum(II)] hexafluorophosphate ([Pt]-[Ir])n. Gel permeation chromatography indicates a degree of polymerization of 9 inferring the presence of an oligomer. Comparison of the absorption and emission band positions and their temperature dependence, emission quantum yields, and lifetimes with those for models containing only the [Pt] or the [Ir] units indicates hybrid excited states including features from both chromophores.  An innovative polymer built upon charged iridium(III), [Ir], and neutral platinum(II) units, [Pt], exhibiting charge transfer excited states [Pt]ā[Ir], has been prepared. The absorption and emission spectra exhibit features reminiscent of both chromophores and the emission lifetimes and quantum yields are intermediate between those for the isolated units, indicating a unique case of formation of hybrid excited states.
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Synthesis of Block Copolymers by Combination of Atom Transfer Radical Polymerization and Visible Light-Induced Free Radical Promoted Cationic Polymerization
AbstractA new synthetic approach for the preparation of block copolymers by mechanistic transformation from atom transfer radical polymerization (ATRP) to visible light-induced free radical promoted cationic polymerization is described. A series of halide end-functionalized polystyrenes with different molecular weights synthesized by ATRP were utilized as macro-coinitiators in dimanganese decacarbonyl [Mn2(CO)10] mediated free radical promoted cationic photopolymerization of cyclohexene oxide or isobutyl vinyl ether. Precursor polymers and corresponding block copolymers were characterized by spectral, chromatographic, and thermal analyses.  A new synthetic route for the preparation of block copolymers by mechanistic transformation from ATRP to visible light-induced free radical promoted cationic polymerization is described. A halide end-functionalized polystyrene synthesized by ATRP is utilized as a macro-coinitiator in dimanganese decacarbonyl [Mn2(CO)10] mediated free radical promoted cationic photopolymerization.
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Modifying the Pores of an Inverse Opal Scaffold With Chitosan Microstructures for Truly Three-Dimensional Cell Culture
AbstractInverse opal scaffolds have recently emerged as a novel class of scaffolds with uniform and controllable pore sizes for tissue engineering to provide better nutrient transport, a uniform cell distribution, and an adjustable microenvironment for cell differentiation. However, when the pore size of the scaffold is much larger than the dimension of a cell, the cell actually encounters a local 2D environment and the void space associated with the pore can not be efficiently utilized. Here, we demonstrate that a truly 3D microenvironment can be created inside a pore by further functionalizing the as-prepared inverse opal scaffold with a second polymer by freeze-drying. The resultant inverse opal scaffold with hierarchically structured pores can enhance both cell proliferation and tissue infiltration.  A facile method has been developed for modifying the pores of an inverse opal scaffold with chitosan microstructures when the pore size of the scaffold is much larger than the dimension of a stretching cell. The resultant inverse opal scaffold with hierarchically structured pores could enhance both cell proliferation and tissue infiltration.
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Synthesis of Main-Chain Metallo-Copolymers Containing Donor and Acceptor Bis-Terpyridyl Ligands for Photovoltaic Applications
AbstractTwo random (ZnII-based P1āP2) and two alternating (RuII-based P3āP4) metallo-copolymers containing bis-terpyridyl ligands with various central donor (i.e., fluorene or carbazole) and acceptor (i.e., benzothiadiazole) moieties were synthesized. The effects of electron donorāacceptor interactions with metal (ZnII and RuII) ions on their thermal, optical, and electrochemical properties were investigated. Because of the strong ICT transitions between donor and acceptor ligands in both ZnII- and RuII-based metallo-coplymers and MLCT transitions in RuII-based metallo-coplymers, the absorption spectra covered a broad range of 260ā750 nm with the band gaps of 1.57ā1.77 eV. In addition, the introduction of RuII-based metallo-coplymer P4 mixed with PC60BM as an active layer of the BHJ solar cell device exhibited the highest PCE value up to 0.90%.  ZnII and RuII metallo-copolymers composed of donor- and acceptor-substituted bis-terpyridyl ligands were synthesized and their electo-optical properties were investigated. Compared with the other conjugated polyelectrolytes, the PVC device with a configuration of ITO/PEDOT:PSS/P4:PC61BM (1:1, w/w)/Ca/Al yielded the highest PCE value of 0.90% with Voc = 0.70 V, Jsc = 3.50 mA cmā2, and FF = 0.37.
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Temperature-Responsive Aqueous Micelles From Terpyridine End-Capped Poly(N-Isopropylacrylamide)-Block-Polystyrene Diblock Copolymers
AbstractAn attractive concept for designing āsmart materialsā is the combination of supramolecular interactions with thermoresponsive polymers. Here, this concept is illustrated by preparing aqueous micelles from poly(N-isopropylacrylamide)-block-polystyrene copolymers functionalized at the extremity of their poly(N-isopropylacrylamide) coronal chains by terpyridine ligands. The effect of temperature and of the addition of Zn(II) ions on the self-assembling properties is then studied.  Aqueous micelles have been prepared from poly(N-isopropylacrylamide)- block-polystyrene copolymers functionalized at the extremity of their poly(N-isopropylacrylamide) coronal chains by terpyridine ligands. The effect of temperature and of the addition of Zn(II) ions on those micelles has been then studied.
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Phase Separation Dynamics of Aqueous Poly [(2-ethoxy) ethoxy ethyl vinyl ether] Solutions as Explored using the Laser T-Jump Technique Combined With Photometry
AbstractPoly[(2-ethoxy) ethoxy ethyl vinyl ether] (poly(EOEOVE)) is a representative thermoresponsive polymer in aqueous solution for which the time constants of the phase separation (PS) are determined with high accuracy. It is revealed that the PS dynamics of the polymer are entirely different from those of the poly(N-isopropylacrylamide) (PNIPAM) system, which is an alternative representative thermoresponsive polymer. Poly(EOEOVE) exhibits complicated PS behavior that is described using double exponential functions. The PS of poly(EOEOVE) is much faster than the PS of PNIPAM in aqueous solutions and becomes faster with increasing concentration of the polymer. PS behavior that is particular to the present system is successfully understood within the framework of the aggregation mechanism.  For aqueous solutions of temperature-responsive polymers, the time constant (Ļ) for phase separation (demixing) with lower critical solution temperature is systematically determined. It is revealed that Ļ is very sensitive to the chemical structure, molecular weight, and the concentration of the sample polymers. The polymer system [poly(EOEOVE)] can respond much rapidly than poly(N-isopropylacrylamide) system.
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Core-Shell Structures of Oligosaccharide-Functionalized Hyperbranched Poly(ethylene imines)
AbstractHyperbranched poly(ethylene imine)s (PEIs) functionalized with maltose, maltotriose, and maltoheptaose form distinct core-shell globular nanoparticles as revealed by small-angle X-ray scattering (SAXS). The solution structures are quantified using the Beaucage unified exponential/power-law approach. SAXS results were confirmed with dynamic light scattering (DLS). We found that all PEI structures are completely insensitive to changes of temperature (5 Ā°C < T < 80 Ā°C) and pH (1 < pH < 10). This remarkable stability of a compact spherical polymeric structure makes the modified PEIs promising for a wide range of biomedical applications.  The characterization of very stable polyelectrolyte core-shell structures is presented, based on temperature- and pH-dependent SAXS and DLS measurements. We hypothesize that the stability of the observed globular nanostructures is resultant from PEIs' unique combination of branching, charging, and amine group mixture.
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Molecular Bottlebrushes with Polypeptide Backbone Prepared via Ring-Opening Polymerization of NCA and ATRP
AbstractA new type of molecular bottlebrush with poly-L-lysine (PLL) as backbone was synthesized via ROP followed by ATRP. A NĻµ-bromoisobutyryl functionalized NĪ±-CBZ-L-lysine was firstly synthesized and converted in polymerizable Ī±-amino acid N-carboxyanhydride (NCA), which was then polymerized using Ni(0) transition metal complex to give well-defined bromo-functionalized homopolypeptide (PBrLL), from which we prepared two types of polypeptide bottlebrushes with polystyrene and poly(oligoethylene glycol methacrylate) as side-chains. PBrLL macroinitiator was demonstrated to have high initiation efficiency for ATRP, which allowed good control over side-chain length. CD and FTIR characterization revealed that both PBrLL macroinitiator and PLL backbone of bottlebrushes adopted Ī±-helical conformation in appropriate solvents.  We report the design and synthesis of molecular bottlebrush bearing poly-l-lysine as backbone. A new bromo-functionalized homopolypeptide is synthesized via ring-opening polymerization, which is then used as an efficient macroinitiator for atom transfer radical polymerization of side chains to give well-defined polypeptide bottlebrushes.
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