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One of the important challenges in designing robust alkaline anion exchange membranes is the difficulty associated with the chemical stability of covalently bound cationic units. Here, a systematic study exploring alkaline stabilities of polymerizable hexyltrimethylammonium cations is presented, where the hexyl chain is linked to a phenyl ring through a direct carbon‐carbon, phenyl ether, or benzyl ether functionality. For this work, small molecule model compounds, styrenic monomer analogs, and their homopolymers are synthesized. Alkaline stabilities of the small molecule cations and their homopolymers are compared to alkaline stability of benzyltrimethylammonium (BTMA) cation and its homopolymer poly(BTMA), respectively. All the hexyl‐tethered cations and their homopolymers are significantly more stable under strongly alkaline conditions (2 m KOD at 80 °C). Moreover, ether‐linked cations show comparable stability to the direct carbon‐carbon linked cation. Via 1H NMR analyses, possible degradation mechanisms are investigated for each small molecule cation. Findings of this study strongly suggest that the alkaline stability is dictated by the steric hindrance around the β‐hydrogen. This study expands beyond the limits of general knowledge on alkaline stability of alkyl‐tethered ammonium cations via the Hofmann elimination route, highlights important design parameters for stable ammonium cations, and demonstrates accessible directly polymerizable alkaline stable ammonium cations. [ABSTRACT FROM AUTHOR]

The length of pendant side chains in charged, random, comb‐shaped polymers dictates the nature of their short‐range ordering. Random copolymers, and terpolymer, of 4‐vinylpyridine (4VP), styrene, and isoprene were synthesized and subsequently fully quaternized with 1‐alkylbromides having varying number of carbons on the alkyl group ranging from 2 to 8. Evaluation by wide angle X‐ray scattering revealed that dipole–dipole attraction facilitates the formation of ionomer cluster morphology in samples with two carbons on the pendant side chain, whereas for samples with four or more carbons on the pendant side chains, side‐chain sterics was dominant resulting in periodic backbone spacing. Copolymers with isoprene, having flexible backbones, favor the formation of ionomer cluster morphology while styrene copolymers having rigid backbones disfavor the formation of ionomer clusters. An "in‐line" dipole model was developed to predict the separation distance at which both ionomer cluster and backbone–backbone morphologies could coexist. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1325–1336 [ABSTRACT FROM AUTHOR]

Abstract: A method to overcome the brittleness of poly (l-lactic acid) (PLLA) by kinetically trapping a continuous low T g amorphous phase is presented. This morphology is accomplished by exploiting the significant difference in the crystallization temperatures of PLLA vs its stereocomplex with the poly (d-lactic acid) (PDLA) isomer. In our studies, the D isomer is the end block of a triblock copolymer with a configuration of the form PDLAn–Soft Blockm–PDLAn. As demonstrated in this study, when blended with PLLA, the obtained morphology, and improvement in the sample toughness and flexibility, strongly depend on the miscibility of the midblock in the triblock copolymer with the matrix PLLA. The difference in the chemical nature of the midblock clearly affected the stereocomplex crystallization between the PDLA end blocks, the PLLA matrix polymer, and the morphology formed. It is found that the miscible midblock gives rise to a soft continuous amorphous phase while in the case of an immiscible midblock, a glassy phase separated amorphous phase is formed. Dramatically different physical properties can be obtained for various PLLA/triblock copolymer blends giving access to tough, yet flexible, semicrystalline PLLA blends. [Copyright &y& Elsevier]

Abstract: A method for selective N-protection of hydroxyalkylbenzimidazoles using 2,2,2-trichloroethylchloroformate (Troc-Cl) applicable to various alkyl chain lengths has been developed. In the specific case of 5-(1-[2,2,2-trichloroethyl formyl]-benzimidazol-2-yl)-propan-1-ol, migration of Troc from the benzimidazole to the primary alcohol occurs in the presence of triethylamine, allowing the choice of selective N-Troc or O-Troc protection. [Copyright &y& Elsevier]

Cyclic ketene acetals (CKAs) possess unique features in two aspects. On one hand, after the addition of a radical on the alkene, CKAs can undergo ring‐opening via radical rearrangement, enabling polyester preparation based on chain‐growth polymerization. On the other hand, the alkene connected with two electron‐donating oxygens in a strained form exhibit unique reactivities, resulting in complex reactions in the presence of electron deficient compounds. In this investigation, fundamental studies on CKA radical ring‐opening polymerization and charge‐mediated reactions were performed. Alternating copolymers of CKA and maleimides, or maleates, were prepared and characterized. Quantum chemistry modeling from the perspectives of reaction kinetics and thermodynamics enabled an in‐depth mechanistic study on the side reactions between CKA and maleic anhydride or itaconic anhydride, inspiring the techniques to minimize those side reactions in competition with radical copolymerization. After purifying the anhydride monomers with sublimation, the copolymerization with CKA successfully occurred. The anhydride containing polyester structures with an alternating sequence were confirmed with comprehensive characterizations. Facile post‐functionalization with an alcohol was performed, resulting in carboxylate containing polyesters. [ABSTRACT FROM AUTHOR]

The phase behavior of block copolymers (BCPs) at the water‐oil interface is influenced by the segmental interaction parameter (χ ${\chi }$) and chain architecture. We synthesized a series of star block copolymers (s‐BCPs) having polystyrene (PS) as core and poly(2‐vinylpyridine) (P2VP) as corona. The interaction parameters of block‐block (χ ${\chi }$ PS‐P2VP) and block‐solvent (χ ${\chi }$ P2VP‐solvent) were varied by adjusting the pH of the aqueous solution. Lowering pH increased the fraction of quaternized‐P2VP (Q‐P2VP) with enhanced hydrophilicity. By transferring the equilibrated interfacial assemblies, morphologies ranging from bicontinuous films at pH of 7 and 3.1 to nanoporous and nanotubular structure at pH of 0.65 were observed. The nanoporous films formed hexagonally packed pores in s‐BCP matrix, while nanotubes comprised Q‐P2VP as corona and PS as core. Control over pore size, d‐spacing between pores, and nanotube diameters was achieved by varying polymer concentration, molecular weight, volume fraction and arm number of s‐BCPs. Large‐scale nanoporous films were obtained by freeze‐drying emulsions. Remarkably, the morphologies of linear BCPs were inverted, forming hexagonal‐packed rigid spherical micelles with Q‐P2VP as core and PS as corona in multilayer. This work provides insights of phase behaviors of BCP at fluids interface and offer a facile approach to prepare nanoporous film with well‐controlled pore structure. [ABSTRACT FROM AUTHOR]

The phase behavior of block copolymers (BCPs) at the water‐oil interface is influenced by the segmental interaction parameter (χ ${\chi }$) and chain architecture. We synthesized a series of star block copolymers (s‐BCPs) having polystyrene (PS) as core and poly(2‐vinylpyridine) (P2VP) as corona. The interaction parameters of block‐block (χ ${\chi }$ PS‐P2VP) and block‐solvent (χ ${\chi }$ P2VP‐solvent) were varied by adjusting the pH of the aqueous solution. Lowering pH increased the fraction of quaternized‐P2VP (Q‐P2VP) with enhanced hydrophilicity. By transferring the equilibrated interfacial assemblies, morphologies ranging from bicontinuous films at pH of 7 and 3.1 to nanoporous and nanotubular structure at pH of 0.65 were observed. The nanoporous films formed hexagonally packed pores in s‐BCP matrix, while nanotubes comprised Q‐P2VP as corona and PS as core. Control over pore size, d‐spacing between pores, and nanotube diameters was achieved by varying polymer concentration, molecular weight, volume fraction and arm number of s‐BCPs. Large‐scale nanoporous films were obtained by freeze‐drying emulsions. Remarkably, the morphologies of linear BCPs were inverted, forming hexagonal‐packed rigid spherical micelles with Q‐P2VP as core and PS as corona in multilayer. This work provides insights of phase behaviors of BCP at fluids interface and offer a facile approach to prepare nanoporous film with well‐controlled pore structure. [ABSTRACT FROM AUTHOR]

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]

The (bio)degradability of cyclic ketene acetal (CKA)-containing polymers is dependent on the polymer structure and degradation conditions. Copolymers of N -vinyl pyrrolidone (N VP), with different CKA comonomers and architectures, were subjected to (bio)degradation under alkaline, enzymatic and wastewater conditions. Grafting CKA- co - N VP moieties onto a poly(ethylene oxide) (PEO) backbone promoted the enzymatic hydrolysis of CKA esters and improved the overall polymer biodegradability. Limited biodegradation was observed for poly(CKA- co - N VP) in the presence of wastewater sludge during an industrial biodegradability test under OECD 301F guidelines. Under less stringent test conditions poly(CKA- co - N VP) achieves small, yet non-negligible biodegradation. Structural analysis of the degradation products shed light into the degradation mechanisms, revealing CKA ester hydrolysis in all cases, while in presence of wastewater sludge, additional CKA end-group oxidation was clearly observed. However, effective amide hydrolysis or pyrrolidone unit biodegradation was not detected, with pyrrolidone-containing segments persisting through the biodegradation test. [Display omitted] • Radical ring-opening copolymerization preparation of water-soluble copolymers. • Alkaline hydrolysis of the copolymers reveals copolymer sequence distributions. • Under enzymatic degradation conditions, Cutinases induced the fastest hydrolysis. • Industrial respirometry assays were used to determine biodegradability. • The biodegradation pathways revealed the limiting factor for polymer degradability. [ABSTRACT FROM AUTHOR]

ABSTRACT This short review is meant to provide the reader with highlights in anion exchange membrane research, describe current needs in the field, and point out promising directions for future work. Anion exchange membranes (AEMs) provide one possible route to low platinum or platinum-free fuel cells with the potential for facile oxidation of complex fuels beyond hydrogen and methanol. AEMs and related stable cationic polymers also have applications in energy storage and other electrochemical technologies such as water electrolyzers and redox flow batteries. While anion exchange membranes have been known for a long time in water treatment applications, materials for electrochemical technology with robust mechanical properties in thin film format have only recently become more widely available. High hydroxide and bicarbonate anion conductivity have been demonstrated in a range of AEM formats, but intrinsic stability of the polymers and demonstration of long device lifetime remain major roadblocks. Novel approaches to stable materials have focused on new types of cations that employ delocalization and steric shielding of the positive center to mitigate nucleophilic attack by hydroxide. A number of promising polymer backbones and membrane architectures have been identified, but limited device testing and a lack of understanding of the degradation mechanisms in operating devices is slowing progress on engineered systems with alkaline fuel cell technology. Our objective is to spur more research in this area to develop fuel cell systems that approach the costs of inexpensive batteries for large-scale applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1727-1735, 2013 [ABSTRACT FROM AUTHOR]

Abstract: The incorporation of the triblock copolymer (PDLA-PEG-PDLA) into Poly(l-Lactic Acid) (PLLA) has produced a semicrystalline polymer of substantial modulus and strength. These improvements in mechanical properties could potentially increase the utility of this biomass-based polymer. The blended samples have a continuous amorphous phase with crystalline regions being the discontinuous portion. Micro-Raman spectroscopy revealed that a stereocomplex involving PDLA and PLLA chains exists in the crystalline region. It can be concluded that the poly(ethylene glycol), the flexible midblock component, is necessarily dispersed in these crystalline regions. Both morphological features can contribute to the improvement in mechanical properties. Therefore, the successful toughening of PLA may be achieved due to several mechanisms working synergistically. [Copyright &y& Elsevier]

Abstract: Hybrid inorganic–organic polymer electrolyte membranes (PEM) were synthesized from a combination of 1H-1,2,3-triazole grafted alkoxy silanes, tetraethoxy silane (TEOS), polyethylene glycol (PEG) and trifluoroacetic acid (TFA) or phosphoric acid. The resulting hybrid inorganic–organic proton exchange membranes were self-supporting and thermally stable up to 180°C. Evaluation of proton conductivity as a function of temperature indicates that by using sol–gel chemistry, it is possible to achieve mechanically robust membranes having proton conductivity comparable to uncrosslinked, liquid-like 1H-1,2,3-triazole functionalized polysiloxane homopolymer. Mechanical properties of these hybrid inorganic–organic membranes were investigated using nanoindentation. [ABSTRACT FROM AUTHOR]

Abstract: Recent developments in single-site catalysis (SSC) have led to many interesting discoveries in ethylene and α-olefin copolymerizations. Here, we report the synthesis of, and polymerizations with, supported piano-stool catalysts and their related analogues. CpTiCl3, Cp*TiCl3, TMSCpTiCl3, and (TMS)2CpTiCl3 were covalently bound to a poly(styrene-r-4-hydroxystyrene) copolymer, affording macroligated catalysts. Ethylene/1-octene and ethylene/styrene copolymerizations with each of these supported catalysts were attempted with cocatalysts including methyl aluminoxane, B(C6F5)3, [Ph3C][B(C6F5)4], and [PhN(CH3)2H][B(C6F5)4]. To determine the effects that the macroligand and the substituents on the cyclopentadienyl ring have on polymer yield and activity, comonomer incorporation, polymer composition, molecular weight, polydispersity index, melting point, and crystallization behavior were investigated. We discovered that the catalysts have vastly different, yet interesting, effects on ethylene/1-octene (EO) and ethylene/styrene (ES) copolymerizations. For ethylene/1-octene copolymers, the activity of the supported catalysts and the amount of 1-octene incorporated into the copolymer is dependent upon the substituents on the cyclopentadienyl ring. The formation of EO copolymers using supported aryloxy-based cyclopentadienyl complexes can also be used as additional evidence for the presence of the tethered aryloxy moiety. The copolymer composition and the thermal properties of these copolymers were also studied. Ethylene/styrene copolymerizations produced polymers with varying characteristics specific to the catalyst employed for the polymerizations. Polymers synthesized with the supported CpTiCl3 and TMSCpTiCl3 displayed both polyethylene and syndiotactic polystyrene melting points. Conversely, polymers synthesized with the supported Cp*TiCl3 displayed only a polyethylene melting point, while polymers prepared with the supported (TMS)2CpTiCl3 displayed only a syndiotactic polystyrene melting point. These findings suggest that copolymerization of ethylene and styrene is not possible with these catalysts. Analysis of the homopolymerizations of styrene and ethylene with Cp*TiCl3 and (TMS)2CpTiCl3, respectively, shows significantly lower activities, leading to preferential polymerization of the more active monomer during copolymerization. [Copyright &y& Elsevier]

Investigates the preparation of cadmium selenide-polyolefin composites from phosphine oxides and ruthenium-based metathesis. Stabilization of cadmium selenide nanoparticles with phosphine oxide; Applicability of semiconductor nanoparticles in biotechnology; Properties of semiconductor nanoparticles.

Ionic conductivity in a polymeric fuel cell requires water uptake. Previous theoretical studies of water uptake used idealized parameters. We report a parameter-free prediction of the water-swelling behavior of a model fuel cell membrane. The model polymers, poly(methyl-butylene)-block-poly(vinylbenzyl-trimethylamine), form lamellar domains that absorb water in humid air. We use the Scheutjens-Fleer methodology to predict the resulting change in lamellar structure and compare with x-ray scattering. The results suggest locally uniform water distributions. However, under conditions where a PVBTMA and water mixture phase-separate, the two phases arrange into stripes with a dilute stripe sandwiched between two concentrated stripes. A small amount of water enhances conductivity most when it is partitioned into such channels, improving fuel-cell performance. [ABSTRACT FROM AUTHOR]

Polyfluorene with p-carborane in the backbone was synthesized from the new monomer 1,12-bis(7-bromo-9,9-dihexyl-9Hfluoren-2-yl)-closo-1,12-dicarbodecaborane to give a high MW, soluble, blue-emitting material characterized by NMR, UV-vis, and fluorescence spectroscopy. [ABSTRACT FROM AUTHOR]

Polyfluorene with p-carborane in the backbone was synthesized from the new monomer 1,12-bis(7-bromo-9,9-dihexyl-9H-fluoren-2-yl)-closo-1,12-dicarbodecaborane to give a high MW, soluble, blue-emitting material characterized by NMR, UV-vis, and fluorescence spectroscopy. [ABSTRACT FROM AUTHOR]

Imino- and amino-pyridine ligands are versatile scaffolds to probe how ligand sterics influence polymerization outcomes for nickel(II) ethylene polymerization catalysts. Six imino- and one amino-pyridine nickel(II) complexes with varied imino/amino-carbon substitution (R 1  = methyl, ethyl, isopropyl or tert -butyl) were synthesized ( 1 - 7 ). Five of these complexes were analyzed crystallographically: dimeric {[2-[(2,6-Me 2 -C 6 H 3 )N=C(R 1 )]C 5 H 4 N]NiBr 2 } 2 (R 1  = Et 2 ; R 1  =  t -Bu 4 ), monomeric [2-[(2,6-Me 2 -C 6 H 3 )N=C(R 1 )]C 5 H 4 N]NiBr 2 NCCH 3 (R 1  = Me 5 ; R 1  =  t -Bu 6 ), and monomeric [2-[(2,6-Me 2 -C 6 H 3 )NHCH( t -Bu)]C 5 H 4 N]NiBr 2 ( 7 ). Complexes 1 - 7 are competent ethylene polymerization precatalysts at 0 ° C, and tert -butyl substituted imino-pyridine precatalysts 4 and 6 and amino-pyridine precatalyst 7 display the best activity, highest polyethylene molecular weight, and narrowest dispersity values of series. 13 C-NMR analyses of polyethylene samples reveal a lightly branched morphology with a modest amount of methyl branching; polymer T m values are consistent with this assessment. Ongoing work includes further exploration of precatalysts 4 , 6 , and 7 in attempt to maximize polyethylene molecular weight and achieve living polymerization. [ABSTRACT FROM AUTHOR]

A polychloromethylstyrene- b- polypolycyclooctene- b -polychloromethylstyrene ABA triblock polymer was used as a backbone in a study to produce a chemically and mechanically robust anion exchange membrane (AEM). The material is easily scalable and the polypolycyclooctene segment (low T m ) makes the membrane flexible to handle. Comparison of the non-crosslinked triblock polymer functionalized with different cations namely; piperidinium, pyrrolidinium, tris(2,4,6-trimethoxyphenyl) phosphonium, and the benchmark trimethylammonium cation showed that the piperidinium functionalized membrane with an ionic exchange capacity of ca. 1.36 mmol.g − 1 had the highest OH − conductivity ca. 95 mS·cm − 1 at 80 °C, 95% RH, and the highest Cl − conductivity of ca. 31 mS·cm − 1 at 70 °C, 95% RH. The membrane with the piperidinium cation was the most chemically stable when immersed in 1 M KOH at 80 °C (with only 16% degradation after 14 days) compared to all the other cation functionalized membranes studied here. Photo-crosslinking with 1,10-decanedithiol (DT) eliminated the melting behavior of the polycyclooctene black and improved the mechanical stability of the films allowing < 20 μm large area transparent membranes to be produced. The DT cross-linking reduced the membrane swelling on all length scales as shown by small angle X-ray scattering, water uptake, and dimensional swelling data, and allowed the membrane to be fully intact even at fully hydrated states based on the tensile strength measurements. [ABSTRACT FROM AUTHOR]

Anion-exchange membranes (AEMs) consisting of poly(vinyl benzyl trimethylammonium)-b-poly(methylbutylene) of three different ion exchange capacities (IECs), 1.14, 1.64, and 2.03 mequiv g[sup -1], are studied by High-Resolution Thermogravimetry, Modulated Differential Scanning Calorimetry, Dynamic Mechanical Analysis, and Broadband Electrical Spectroscopy in their OH[-] form. The thermal stability and transitions are elucidated, showing a low temperature T[sub g] and a higher temperature transition assigned to a disorder -- order transition, Tg, which depends on the IEC of the material. The electric response is analyzed in detail, allowing the identification of three polarizations (only two of which contribute significantly to the overall conductivity, tf[sub EP] and tf[sub IP1]) and two dielectric relaxation events (β[sub 1] and β[sub 2]), one associated with the tolyl side groups (β[sub 1]) and one with the cationic side chains (β[sub 2]). The obtained results are integrated in a coherent picture and a conductivity mechanism is proposed, involving two distinct conduction pathways, tf[sub EP] and tf[sub IP1]. Importantly, we observed a reordering of the ion pair dipoles which is responsible for the Tg at temperatures higher than 20 °C, which results in a dramatic decrease of the ionic conductivity. Clustering is highly implicated in the higher IEC membrane in the hydroxyl form, which reduces the efficiency of the anionic transport. [ABSTRACT FROM AUTHOR]

Using salt-doped polystyrene- b -poly(2-vinylpyridine) star shaped block copolymer as a model, we show that the architecture of (A- b -B) n type multi-arm star block copolymers enhances the ordering of the block copolymers, enabling the generation of nanostructures with microdomain periods less than 10 nm. The influence of the arm number on the order-to-disorder transition temperature and molecular weight was systematically studied using small angle X-ray scattering. The configurational constraints placed on the chains by anchoring each block copolymer to a central junction point have a significant effect on the disorder-to-order transition behavior. In addition to an increase in the Flory-Huggins parameter ( χ ), block copolymers with multi-arm star shape chain architecture have a critical segregation strength ( χN ) C that decreases with arm number, opening a simple route to generate ordered nanostructures with periods below 10 nm. [ABSTRACT FROM AUTHOR]

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 (<25 wt %) and maintained adequate mechanical properties in both dry and hydrated conditions. X-ray scattering and transmission electron microscopy (TEM) revealed formation of cylindrical non-ionic domains in a connected ionic phase. [ABSTRACT FROM AUTHOR]

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]

Triblock and diblock copolymers based on isoprene (Ip) and chloromethylstyrene (CMS) were synthesized by sequential polymerization using reversible addition-fragmentation chain transfer radical polymerization (RAFT). The block copolymers were quaternized with tris(2,4,6-trimethoxyphenyl)phosphine (Ar3P) to prepare soluble ionomers. The ionomers were cast from chloroform to form anion exchange membranes (AEMs) with highly ordered morphologies. At low volume fractions of ionic blocks, the ionomers formed lamellar morphologies, while at moderate volume fractions (≥30% for triblock and ≥22% for diblock copolymers) hexagonal phases with an ionic matrix were observed. Ion conductivities were higher through the hexagonal phase matrix than in the lamellar phases. Promising chloride conductivities (20 mS/cm) were achieved at elevated temperatures and humidified conditions. [ABSTRACT FROM AUTHOR]

Isotactic Polypropylene-Exfoliated Graphene Nanoplatelet (iPP-xGnP™) nanocomposites were prepared through an in-situ polymerization technique and compared to analogous composites prepared by melt compounding. In-situ preparation of iPP-xGnP nanocomposites was accomplished via single site metallocene polymerization of propylene within a toluene dispersion of xGnP nanoparticles. The in-situ prepared nanocomposites were compared to analogous nanocomposites prepared by melt compounding of commercial Ziegler–Natta iPP with xGnP. Optical microscopy showed the in-situ prepared nanocomposites demonstrated poorer xGnP dispersion compared to composites prepared by melt compounding. All xGnP-reinforced nanocomposites demonstrated increased crystallization temperature, as well as increases in mechanical strength and modulus, relative to neat iPP. However, the non-linear mechanical properties were found to be influenced by the both the preparation method and nanoparticle loading. Nanocomposites prepared by in-situ polymerization generally demonstrated superior ductility and fracture toughness compared to composites prepared by melt compounding. The results are discussed with regard to the preparation technique and xGnP loading. [ABSTRACT FROM AUTHOR]

Random copolymers of isoprene and4-vinylbenzyl chloride (VBCl)with varying compositions were synthesized via nitroxide-mediatedpolymerization. Subsequent quaternization afforded solvent processableand cross-linkable ionomers with a wide range of ion exchange capacities(IECs). Solution cast membranes were thermally cross-linked to formanion exchange membranes. Cross-linking was achieved by taking advantageof the unsaturations on the polyisoprene backbone, without added cross-linkers.A strong correlation was found between water uptake and ion conductivityof the membranes: conductivities of the membranes with IECs beyonda critical value were found to be constant related to their high waterabsorption. Environmentally controlled small-angle X-ray scatteringexperiments revealed a correlation between the average distance betweenionic clusters and the ion conductivity, indicating that a well-connectednetwork of ion clusters is necessary for efficient ion conductionand high ion conductivity. [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.

Front Cover: Instead of using traditional chemical crosslinking, flexible and rubbery poly(lactic acid) can be created by controlling the crystallization process. The stereo complex crystals formed are the “physical crosslinks”. This slide is used to demonstrate the relative crystallization kinetics and the morphology formed for two chemically identical but physically different co‐crystallizing PLA based blends. Further details can be found in the article by S. R. Rathi, D. Ng, E. B. Coughlin,* S. L. Hsu,* C. S. Golub, G. H. Ling, and M. J. Tzivanis on page 320. [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]

Block copolymers of polystyrene- b-poly(vinyl benzyl trimethylammonium tetrafluoroborate) (PS- b-[PVBTMA][BF4]) were synthesized by sequential monomer addition using atom transfer radical polymerization. Membranes of the block copolymers were prepared by drop casting from dimethylformamide. Initial evaluation of the microphase separation in these PS- b-[PVBTMA][BF4] materials via SAXS revealed the formation of spherical, cylindrical, and lamellar morphologies. Block copolymers of polystyrene- b-poly(vinyl benzyl trimethylammonium hydroxide) (PS- b-[PVBTMA][OH]) were prepared as polymeric alkaline anion exchange membranes materials by ion exchange from PS- b-[PVBTMA][BF4] with hydroxide in order to investigate the relationship between morphology and ionic conductivity. Studies of humidity [relative humidity (RH)]-dependent conductivity at 80 °C showed that the conductivity increases with increasing humidity. Moreover, the investigation of the temperature-dependent conductivity at RH = 50, 70, and 90% showed a significant effect of grain boundaries in the membranes against the formation of continuous conductive channels, which is an important requirement for achieving high ion conductivity. © 2012 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1751-1760, 2013 [ABSTRACT FROM AUTHOR]

ABSTRACT The synthesis and characterization of a photocleavable block copolymer containing an ortho-nitrobenzyl (ONB) linker between poly(methyl methacrylate) and poly( d-lactide) blocks is presented here. The block copolymers were synthesized via atom transfer radical polymerization (ATRP) of MMA followed by ring-opening polymerization (ROP) of d-Lactide and ROP of d-lactide followed by ATRP of MMA from a difunctional photoresponsive ONB initiator, respectively. The challenges and limitations during synthesis of the photocleavable block copolymers using the difunctional photoresponsive ONB initiator are discussed. The photocleavage of the copolymers occurs under mild conditions by simple irradiation with 302 nm wavelength UV light (Relative intensity at 7.6 cm: 1500 μW/cm2) for several hours. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4309-4316 [ABSTRACT FROM AUTHOR]

A systematic comparison between graft poly( l-lactide) copolymers with different topologies and their ability to form stereocomplexes with poly( D-lactide) (PDLA) is performed. Comb and hyperbranched copolymers based on functional poly(ethylene glycol) and poly( l-lactide) with molecular weights in the range of 2000-90 000 g mol−1 and moderate molecular weight distributions ( Mw/ Mn = 1.08-1.37) are prepared via the combination of anionic and ring-opening polymerization. Two 'topological isomers,' a linear poly(ethylene oxide)/poly(glycerol) (PEG/PG) copolymer and a branched PEG/PG copolymer are used as backbone polymers. Furthermore, the stereocomplex formation between PDLA and the hyperbranched and comb copolymers containing poly( l-lactide) arms is studied. Stereocomplex formation is confirmed by DSC as well as by Fourier transform IR (FTIR) and Raman spectroscopy. [ABSTRACT FROM AUTHOR]

A seriesof poly(pentafluorophenyl (methyl)acrylates)-block-poly(ethylene oxide) with o-nitrobenzyl ester photocleavablejunctions (PPFP(M)A-hv-PEO) were synthesized by RAFTpolymerization. The block copolymers were used to fabricate thin filmsand fibers by spin-coating and electrospinning, respectively. Aftersolvent annealing, UV exposure, and washing with methanol/water toremove the minor PEO block, nanoporous structures were obtained. Boththe porous thin films and fibers remained reactive to amine substitutionof the pentafluorophenyl esters under mild conditions, which was confirmedby XPS, fluorescence confocal microscopy, FT-IR, and contact anglemeasurements. [ABSTRACT FROM AUTHOR]

We report the facile synthesis and characterization of a class of thienothiophene polymers with various lengths of alkyl side chains. A series of 2-alkylthieno[3,4- b]thiophene monomers (Ttx) have been synthesized in a two-step protocol in an overall yield of 28-37%. Poly(2-alkylthieno[3,4- b]thiophenes) (PTtx, alkyl: pentyl, hexyl, heptyl, octyl, and tridecyl) were synthesized by oxidative polymerization with FeCl3 or via Grignard metathesis (GRIM) polymerization methods. The polymers are readily soluble in common organic solvents. The polymers synthesized by GRIM polymerization method (PTtx-G) have narrower molecular weight distribution ( Đ) with lower molecular weight ( Mn) than those synthesized by oxidative polymerization (PTtx-O). The band structures of the polymers with various lengths of alkyl side chains were investigated by UV-vis spectroscopy, cyclic voltammetry, and ultraviolet photoelectron spectroscopy. These low-bandgap polymers are good candidates for organic transistors, organic light-emitting diodes, and organic photovoltaic cells. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 [ABSTRACT FROM AUTHOR]

Abstract: A series of Polyhedral Oligomeric Silsesquioxane (POSS) propylmethacrylate (PMA) and styryl oligomers were prepared from POSS monomers, R7R''Si8O12, containing 1 functional R’ group for polymerization and 7 inert R-groups where R=isobutyl (i-butyl), phenyl (Ph), cyclohexyl (Cy) or cyclopentyl (Cp). Both standard atom transfer radical polymerization (ATRP) and free radical syntheses, the latter employing azoisobutylnitrile as the free radical initiator were used in the syntheses. Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectra were obtained in a new matrix, 4,4′-dihydroxyoctafluoroazobenzene which was especially designed for insoluble and intractable polymeric materials. Well-resolved series of oligomers were observed out to n =∼13 in both the linear and reflectron modes. Major peaks were assigned based on tandem mass spectrometry (MSMS) fragmentation patterns to give a consistent explanation of the observed spectra. In all cases, ionization of the ATRP products gave cationized parent ions in which the terminal Br atom was replaced by hydrogen. Additional observed peaks were due to loss of POSS side chains from the oligomer backbone. The free radical products were terminated with either one or two isobutylnitrile groups. Electrospray ionization (ESI) spectra were more complex than the MALDI-TOF but showed either identical parent ions or closely related hydroxylated parent ions. [Copyright &y& Elsevier]

The effect of anion exchange ionomer (AEI) chemistry on the kinetics of the oxygen evolution reaction (OER) was systematically studied in both half-cell and single-cell electrolysis experiments. OER was studied in 1 M K 2 CO 3 at 50 °C using an array of ionomer-silver catalyst inks deposited on Ni foam. Different ionomer modifications were investigated to optimize the OER performance. The AEI used in this work features a block copolymer backbone of polychloromethylstyrene- b -polycyclooctene- b -polychloromethylstyrene which was functionalized with either benzyltrimethylammonium (TMA) or benzylmethylpiperidinium (MPRD) quaternary ammonium cations. Using an MPRD quaternary ammonium cation shifted the rate determining step at high overpotentials, ultimately providing enhanced performance. Increasing the catalyst ink dilution was also found to substantially improve mass activity and catalyst utilization (increase from 35 to 88 A g−1 Ag), likely by reducing the ionomer thickness and decreasing transport resistances. In the final ionomer modification, the Ni foam substrate was leveraged to partially hydrogenate the polycyclooctene midblock to be polyethylene-like at the Ni interface. A significant increase in the electrochemical surface area (C dl increased from 8.8 to 20.8 mF cm−2) and performance (by 47 mA cm−2 or 29 A g−1 Ag) was observed with the incorporation of polyethylene. Kinetic results from half-cell experiments were validated via single-cell anion exchange membrane electrolysis experiments, where the optimized electrode displayed enhanced performance in both 1 M K 2 CO 3 and DI H 2 O. [ABSTRACT FROM AUTHOR]

Development of improved durable, conductive, and selective anion exchange membranes (AEMs) are critical for electrodialysis. A series of three ABA triblock copolymers derived from polychloromethylstyrene- b -polyethylene- b -polychloromethylstyrene (PCMS- b -PE- b -PCMS), designated as large, 0.8:1, medium, 0.2:1, and small 0.1:1, block AEMs by their PCMS:PE block size were quaternized with methylpiperidine. The water uptake decreases from 100% for the large block AEM to 5% for the small block AEM. At this low water content in liquid water, the small block AEM shows complete ion dissociation, with similar diffusion (2.6 × 10−6 mol m−2 s−1) and E a (24 kJ/mol) as the larger block AEMs. However, a 34% increase in apparent permselectivity was achieved with the small block AEM. In electrodialysis, the small block AEM improved salt removal by 300% compared with a commercial AEM. Under further investigation, migration was shown to be enhanced by 600% in the small block AEM. The small block AEM has a λ = 5 in liquid water, which is too low to explain the chloride conductivity behavior. Furthermore, the permselectivity in the small block AEM is much higher than expected from its small-angle X-ray scattering morphology, indicating there must be a water-rich region of smaller dimensions where cation/anion pairs are fully solvated. [Display omitted] • A triblock copolymer AEM was developed with decreasing hydrophilic block lengths. • Small block has low water uptake and charge density, but full ion dissociation. • Small block achieves enhanced permselectivity and migrative flux. • Small block improves electrodialysis by nearly 300x compared to large block. [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]

From a synthesized cobaltocenium-containing norbornene derivative, norbornene based copolymers with cobaltocenium cations are prepared by ring-opening metathesis polymerization (ROMP). The polymers can be cast into thin robust membranes. The membranes show morphology of disordered interconnected cobaltocenium domains. The high ionic conductivity suggests that such membranes are good candidates for anion exchange membranes. An efficient method to incorporate a cobaltocenium cation into polymers for anion exchange membranes is described. A cobaltocenium-containing norbornene derivative has been synthesized. It can be homopolymerized, or copolymerized with norbornene, by ring-opening metathesis polymerization (ROMP) with quantitative yields. The composition of the random copolymers can be precisely controlled by adjusting the feed ratio of the monomers. The resulting polymers can be cast into thin robust membranes. The morphology of the membranes is characterized by humidity controlled SAXS and TEM, showing disordered interconnected cobaltocenium domains. The high ionic conductivity suggests that such membranes are good candidates for anion exchange membranes. [ABSTRACT FROM AUTHOR]