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Hybrid conjugated polymers containing carborane directly bonded in the aromatic backbone repeat structure have interesting electronic bonding structures and are potentially useful new materials in organic electronics. Conjugated polymers based on o-carborane are particularly interesting for applications in sensing and detection because of the cage's unique bonding scheme and its bent geometry. Poly(fluorene) containing o-carborane displays multiple emission pathways that can be modulated through interactions with small molecules. In this paper, we report that films of poly(fluorene) with o-carborane in the backbone function as vapochromatic photoluminescent sensors toward volatile organic molecules., (© 2011 American Chemical Society)

The regular arrangement of complementary diaminopyridine-thymine (DAP-THY) on alternating copolymers permits cooperative binding events and the effective formation of well-controlled micrometre-scale aggregates.

Star block copolymers (s-BCPs), comprised of multiple linear diblock copolymers joined at a central point, are shown to segregate to the interface between two immiscible homopolymers that are identical to the blocks of the s-BCPs. The s-BCPs undergo a configurational transition at the interface, with different blocks of copolymers being embedded in their respective homopolymers, thereby bridging the interface and promoting adhesion. A series of 4-arm s-BCPs were synthesized with hydrogenated or deuterated polystyrene (PS/dPS) as the core block and poly(2-vinylpyridine) (P2VP) as the corona block, which was directly placed at the interface between the two homopolymers. Neutron reflectivity (NR) was used to determine the concentration profiles of the PS homopolymer, s-BCP core blocks, and P2VP total segments under equilibrium. The investigation varies the molecular weight (MW) and the total number of s-BCPs at the interface. Self-consistent-field theory (SCFT) was also employed to calculate the concentration profiles of the components at the interface, which were in excellent agreement with experimental results. The NR showed that the interfacial width between the homopolymers increased with the increasing number of s-BCPs at the interface up to a saturation limit. Beyond this limit, additional s-BCPs were released into the corona-miscible phase as unimolecular micelles. For a comparable interlayer thickness of s-BCPs at the interface, lower MW s-BCPs generated a broader interface. SCFT analysis suggested that, at the same packing density, the arms of the low MW s-BCPs align more parallel to the interface, while the arms of high MW s-BCPs adopt a more normal orientation, like their linear BCP counterparts. Furthermore, it was also observed that the core blocks, constrained by the junction points, were oriented more parallel and closer to the interface than the corona blocks. The phase behavior of the polymer blends revealed that s-BCP additives can efficiently reduce the domain size, with the low MW yielding smaller domain sizes due to the greater reduction in the interfacial energy and the high MW arresting phase separation due to their higher binding energy and a jamming of the interfacial assemblies. Asymmetric double cantilever beam (ADCB) tests demonstrated that s-BCPs promoted adhesion more efficiently than their linear BCP counterparts due to stronger binding energy per molecule, suggesting a more efficient compatibilizer for polymer upcycling. The results from these studies provide fundamental insights into the assembly of s-BCPs at homopolymer interfaces, the reduction of domain size, and promotion of adhesion, providing a strategy for the use of s-BCPs as stealth surfactants and universal compatibilizers.

Anion exchange membranes (AEMs) are a promising class of materials for applications that require selective ion transport, such as fuel cells, water purification, and electrolysis devices. Studies of structure–morphology–property relationships of ion-exchange membranes revealed that block copolymers exhibit improved ion conductivity and mechanical properties due to their microphase-separated morphologies with well-defined ionic domains. While most studies focused on symmetric diblock or triblock copolymers, here, the first example of a midblock quaternized pentablock AEM is presented. A symmetric ABCBA pentablock copolymer was functionalized to obtain a midblock brominated polymer. Solution cast films were then quaternized to obtain AEMs with resulting ion exchange capacities (IEC) ranging from 0.4 to 0.9 mmol/g. Despite the relatively low IEC, the polymers were highly conductive (up to 60 mS/cm Br− at 90 °C and 95%RH) with low water absorption (

The crystallization behavior of two chemically identical but physically different co-crystallizing poly( l-lactic acid) (PLLA)-based blends is studied. The first set studied involves an all- l unit polymer (PLLA) co-crystallizing with a PDLA-miscible soft polyether-PDLA triblock copoly­mer, where d refers to the d isomer. The second set studied involves homopolymer blends of PLLA/miscible soft polyether/PDLA with compositions identical to the first set. Crystallization is performed under isothermal and non-isothermal crystallization conditions and the crystallization kinetics, crystal perfection, and the blend morphology are investigated. It is clear that the stereocomplex crystallization is significantly slower in the triblock copolymer blends in comparison with the homopolymer blends. Furthermore, based on diffraction, spectroscopic, and thermal data, it is found that the stereocomplex crystals formed in the homopolymer blends achieve higher order and perfection, with a melting temperature 15-20 °C higher than those formed in the triblock blends. [ABSTRACT FROM AUTHOR]

A correction to the article "Anion Exchange Membranes: Current Status and Moving Forward" by Michael A. Hickner, Andrew M. Herring and E. Bryan Coughlin that was published in a 2013 issue of the "Journal of Polymer Science Part B: Polymer Physics" is presented.

Cellulose nanocrystals (CNCs) naturally self-assemble into helical structures that effectively deflect crack propagation and exhibit structural coloration based on the pitch. To further tune the structural coloration via environmental conditions, a thermoresponsive polymer poly(diethylene glycol methyl methacrylate) (PMEO 2 MA) was incorporated into CNC composites. Nanocomposite films of PMEO 2 MA-CNC with 0–30 mass % PMEO 2 MA loadings were prepared via controlled evaporation-induced self-assembly. As the polymer infiltrates CNCs' helical structure, the resulting films' reflectance wavelength transitions from blue to red. PMEO 2 MA-CNC nanocomposites exhibited reversible temperature responses in the solid-state between 26 °C and 29 °C under variable humidity conditions, demonstrating the tunability of the self-assembled films. Fluorescence lifetime imaging microscopy (FLIM) provided insights to polymer dynamics in response to temperature. [Display omitted] • Thermoresponsive polymer can tune structural coloration of cellulose nanocrystals. • Hydration level and temperature of CNC composite determines optical response. • Reversible LCST behavior of CNC composites. • FLIM provides insights into polymer dynamics in response to temperature changes. [ABSTRACT FROM AUTHOR]

The performance of organic photovoltaics(OPVs) is heavily dependenton the structure and functionalization of the conjugated polymer usedin the active absorbing layer. Using a set of materials based on poly(thieno[3,4-b]thiophene-alt-benzodithiophene) withdifferent alkyl, aryl, perfluoroalkyl, and perfluoroaryl pendant functionalities,we have studied the correlation between absorbance, morphology, crystallinity,charge mobility, and the OPV performance in an effort to identifystructure-performance relationships. The perfluorinated pendants onPTF8B and PTFPB were shown to significantly enhance the Vocin the OPV devices (by ∼0.2 V), but also inducedthe formation of larger phase separated PCBM-rich domains. PT8B andPTFPB devices reached average efficiencies of ∼3.2%. [ABSTRACT FROM AUTHOR]

Abstract: The thermal degradation behavior of novel ultra-fire-resistant polymers and copolymers containing deoxybenzoin units in the backbone was studied by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The polymers were synthesized by the polycondensation of 4,4′-bishydroxydeoxybenzoin (BHDB) with isophthaloyl chloride (to give polyarylates), phenylphosphonic dichloride (to give polyphosphonates), and their mixtures (to give poly(arylate-co-phosphonate) copolymers). The thermal decomposition, under nitrogen conditions, of BHDB-polyarylate was characterized by a simultaneous degradation of both the bisphenolic (deoxybenzoin) and isophthalate sub-units, whereas a three-step decomposition phenomenon was observed for the BHDB-polyphosphonate. BHDB-polymers containing phosphonate groups in the backbone did not show any phosphorus-based volatile decomposition products, whereas the corresponding bisphenol A-based polyphosphonates released volatile decomposition products comprised mainly of phosphorus-containing compounds. [Copyright &y& Elsevier]

Abstract: Random copolymer and terpolymers of 1,2,3-triazole-containing acrylates and poly(ethylene glycol)methyl ether acrylate (PEGMEA) have been synthesized and characterized. Proton conductivity measurements were made using impedance spectroscopy. The range of conductivity values from 80 °C to 200 °C spans only 1.5 orders of magnitude, demonstrating reduced temperature dependence over previously reported heterocycle based anhydrous proton conducting membranes. Introduction of PEG graft chains increased conductivity on both an absolute and T–Tg normalized scale up to 30 mol% PEGMEA. Further increases in conductivity were achieved through addition of trifluoroacetic acid where increases of 0.5 to 1.5 orders of magnitude were observed depending on doping level. [Copyright &y& Elsevier]

Abstract: Proton conducting polymers and copolymers containing tethered benzimidazole moieties spanning a wide range of glass transition temperatures (2–113 °C) have been prepared. Conductivity versus temperature plots of the homopolymers display the competing effects of mobility and charge carrier density. Consistent with literature reports, T g values of benzimidazole-containing polymers increased over the parent polymer, however, successful reduction of T g was accomplished by copolymerizing a benzimidazole functional acrylate monomer (B5A) with poly(ethylene glycol) methyl ether acrylate (PEGMEA). The reduction in T g is thought to occur through disruption of intermolecular forces between benzimidazole units. Evaluation of conductivity as a function of temperature by ac impedance methods indicate that decreasing T g through copolymerization results in conductivity increases over the low and intermediate temperature range (40–160 °C). Copolymer T g decreases with increasing PEGMEA content, and conductivity at 40 °C can be increased by nearly 2.5 orders of magnitude over B5A homopolymer. However, conductivity at high temperatures (>160 °C) decreases due to charge carrier dilution by the addition of PEGMEA. [Copyright &y& Elsevier]

Amphiphilic cationic polynorbomene derivatives, soluble in water, were prepared from modular norbornene monomers, with a wide range of molecular weights (Mn = 1600-137 500 g/mol) and narrow polydispersities (PDl = 1.1-1.3). The antibacterial activity determined by growth inhibition assays and the hemolytic activity against human red blood cells were measured and compared to determine the selectivity of the polymers for bacterial over mammalian cells. The effects of monomer repeat unit hydrophobicity and polymer molecular weight on antibacterial and hemolytic activities were determined. The hydrophobicity of the repeat unit was observed to have dramatic effects on antibacterial and hemolytic activities. Lipid membrane disruption activities of the polymers was confirmed by measuring polymer-induced dye leakage from large unilamellar vesicles. By tuning the overall hydrophobicity of the polymer through random copolymerizations of modular norbornene derivatives, highly selective, nonhemolytic antibacterial activities were obtained. For appropriate monomer composition, selectivity against bacteria versus human red blood cells was determined to be over 100. [ABSTRACT FROM AUTHOR]