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ABSTRACT: Reversible addition‐fragmentation chain transfer (RAFT) polymerization produced novel ABA triblock copolymers with associative urea sites within pendant groups in the external hard blocks. The ABA triblock copolymers served as models to study the influence of pendant hydrogen bonding on polymer physical properties and morphology. The triblock copolymers consisted of a soft central block of poly(di(ethylene glycol) methyl ether methacrylate) (polyDEGMEMA, 58 kg/mol) and hard copolymer external blocks of poly(2‐(3‐hexylureido)ethyl methacrylate‐co‐2‐(3‐phenylureido)ethyl methacrylate) (polyUrMA, 18‐116 kg/mol). Copolymerization of 2‐(3‐hexylureido)ethyl methacrylate (HUrMA) and 2‐(3‐phenylureido)ethyl methacrylate (PhUrMA) imparted tunable hard block Tg's from 69 to 134 °C. Tunable hard block Tg's afforded versatile thermomechanical properties for diverse applications. Dynamic mechanical analysis (DMA) of the triblock copolymers exhibited high modulus plateau regions (∼100 MPa) over a wide temperature range (−10 to 90 °C), which was indicative of microphase separation. Atomic force microscopy (AFM) confirmed surface microphase separation with various morphologies. Variable temperature FTIR (VT‐FTIR) revealed the presence of both monodentate and bidentate hydrogen bonding, and pendant hydrogen bonding remained as an ordered structure to higher than expected temperatures. This study presents a fundamental understanding of the influence of hydrogen bonding on polymer physical properties and reveals the response of pendant urea hydrogen bonding as a function of temperature as compared to main chain polyureas. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1844–1852 [ABSTRACT FROM AUTHOR]

Living anionic polymerization of 4-diphenylphosphino styrene ( DPPS) achieved unprecedented poly(S- b-I- b- DPPS) ABC triblock copolymers with predictable molecular weights and narrow polydispersities. In situ Fourier transform infrared spectroscopy probed the anionic polymerization, monitoring vinyl disappearance during sequential monomer addition for kinetic analysis. Varying the concentration of reinforcing, polystyrenic external blocks enabled diverse compositions with tunable thermomechanical properties and tailored morphology. Dynamic mechanical analysis confirmed the presence of microphase separation in the triblock copolymers and revealed a broad temperature range ( ca 100 oC) for a plateau region and onset of flow temperatures above 100 oC. Small-angle X-ray scattering and atomic force microscopy collectively revealed solid state morphologies of the triblock copolymers and probed phase separation at the nanoscale. Well-defined poly(S- b-I- b- DPPS) ABC triblock copolymers with tunable structure − property relationships now permit phosphorus-containing thermoplastic elastomers for emerging applications. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Novel polyurethane (PU) cationomers are synthesized using an imidazolium diol-based ionic liquid (IL) chain extender. A systematic comparison with a non-ionic PU analogue reveals effect of the imidazolium cation on physical properties, hydrogen bonding, and morphology of segmented PU. Casting resulting PU solutions with various contents of IL generates novel membranes. Thermal study reveals that IL-containing PU membranes exhibit a constant soft segment Tg at −81 °C; however, the Tg of imidazolium hard segments systematically shifts to lower temperatures with increasing IL content. This suggests that IL preferentially locates into the imidazolium ionic hard domains, which is also evident in small-angle X-ray scattering. Moreover, dielectric relaxation spectroscopy demonstrates increased ionic conductivity of PU membranes by 5 orders of magnitude upon incorporation of 30 wt% IL. [ABSTRACT FROM AUTHOR]

Conventional melt transesterification successfully produced high-molecular-weight segmented copolyesters. A rigid, high- Tg polyester precursor containing the cycloaliphatic monomers, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and dimethyl-1,4-cyclohexane dicarboxylate allowed molecular weight control and hydroxyl difunctionality through monomer stoichiometric imbalance in the presence of a tin catalyst. Subsequent polymerization of a 4000 g/mol polyol with monomers comprising the low- Tg block yielded high-molecular-weight polymers that exhibited enhanced mechanical properties compared to a nonsegmented copolyester controls and soft segment homopolymers. Reaction between the polyester polyol precursor and a primary or secondary alcohol at melt polymerization temperatures revealed reduced transesterification of the polyester hard segment because of enhanced steric hindrance adjacent to the ester linkages. Differential scanning calorimetry, dynamic mechanical analysis, and tensile testing of the copolyesters supported the formation of a segmented multiblock architecture. Further investigations with atomic force microscopy uncovered unique needle-like, interconnected, microphase separated surface morphologies. Small-angle X-ray scattering confirmed the presence of microphase separation in the segmented copolyesters bulk morphology. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 [ABSTRACT FROM AUTHOR]

Examines the utilization of sulfonated polyester ionomers as minor-component compatibilizers in blends of an amorphous polyester and polyamide. Preparation of the blends using twin-screw extrusion; Blend morphology; Thermal and mechanical properties of the extruded blends.

Abstract: The morphology and physical properties of a pentablock copolymer (PBC) were investigated as a function of sulfonation or ion-exchange capacity (IEC). This material is comprised t-butylstyrene (tBS), hydrogenated isoprene (HI), sulfonated polystyrene (sPS), and polystyrene (PS). Thermally reversible crosslinks are created with tBS, which is dispersed within a rubbery phase of HI, sPS, and PS. A morphology change was observed upon sulfonating PBC. This created abrupt material changes such as water swelling, proton conductivity, and methanol transport at an IEC greater than one. Water, proton, and methanol transport are associated with sPS domains. Gas transport occurs mainly through more permeable HI and tBS phases that were disrupted with increasing IEC. The permeability (P) was modeled using a lamellar morphology. Ion and methanol transport occurred via sulfonated domains. Finally, a structure–property and transport property correlation of this multi-block PBC ionomer is discussed within this paper. [Copyright &y& Elsevier]

Abstract: Poly(ethylene terephthalate) ionomer (PETI)/organically-modified montmorillonite clay (OMC) nanocomposites were prepared via melt extrusion. Sulfonated PET containing various incorporations of ionic comonomer and clay modifications were investigated. The random incorporation of ionic functionalities along the PET backbone enhances interactions between the matrix polymer and montmorillonite clay resulting in the creation of polymer-clay nanocomposites exhibiting a predominately exfoliated morphology. The morphology is correlated with mechanical properties and crystallization behavior. It is found that incorporation of clay into the random ionomers leads to increased mechanical properties and slower crystallization rates. [Copyright &y& Elsevier]

Ionomer chain and solvent molecule interactions during solution-casting, solvent evaporation, and solidification impacts chain entanglements, spatial arrangement of functional groups, microstructure development, morphology, and physical properties. These concepts were investigated using poly( t -butylstyrene- b -ethylene- alt -propylene- b -sulfonatedstyrene- b -ethylene- alt -propylene- b - t -butylstyrene) with a fixed ion-exchange capacity of 1.0, and estimated solubility parameter of 21.8 (J/cm 3 ) 1/2 . Films were solution-cast using an equal volume cyclohexane:heptane mixture (C:H), chloroform (CHCl 3 ), and tetrahydrofuran (THF). Subsequent film structures were evaluated using transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), FT-IR, and electrochemical impedance spectroscopy. A commercially supplied film had sulfonated domains randomly distributed throughout it, and its initial proton conductivity was 11.8 mS/cm. A film created by solution-casting from C:H had a morphology containing randomly distributed sulfonated domains. This random morphology became more ordered with a lamella-like morphology when solution-cast using THF. The film produced from CHCl 3 had a morphology that was between random and ordered. Film morphology differences were attributed to a poorer solvent system that inhibited chain solvation. The solution-cast film’s proton conductivity was 1.0 mS/cm for a random morphology, and 15.3 mS/cm with a lamella-like structure. Increasing the ionomer-THF solution-casting temperature to 40 °C produced a film with a 103% increase in conductivity (31.2 mS/cm). This led to a water uptake change from 29 wt% to 80 wt%. Cycling a THF solution-cast film from its dry to a wet state revealed that a lamella-like morphology would maintain its conductivity, but the commercial film’s conductivity decreased from 11.8 mS/cm to 0.98 mS/cm. Ionomer film properties were found to be dependent upon solvent quality and processing. [ABSTRACT FROM AUTHOR]

Abstract: Poly(ethylene glycol) (PEG)-based sulfonated polyurethanes bearing either sulfonated soft segments (SSSPU) or sulfonated hard segments (SHSPU) were synthesized using sulfonated monomers. Differential scanning calorimetry (DSC) revealed that sulfonate anions either in the soft segments or hard segments both increased the glass transition temperatures (T g’s) of the soft segments and suppressed their crystallization. Moreover, dynamic mechanical analysis (DMA) and tensile analysis demonstrated that SSSPU possessed a higher modulus and tensile strength relative to SHSPU. Fourier transform infrared (FTIR) spectroscopy revealed that hydrogen bonding interactions in SHSPU were suppressed compared to SSSPU and noncharged PU. This observation suggested a high level of phase-mixing for SHSPU. In addition, atomic force microscopy (AFM) phase images revealed that both SSSPU and noncharged PU formed well-defined microphase-separated morphologies, where the hard segments phase-separated into needle-like hard domains at the nanoscale. However, SHSPU showed a phase-mixed morphology, which was attributed to increased compatibility of polar PEG soft segments with sulfonated ionic hard segments and disruption of hydrogen bonds in the hard segment. The phase-mixed morphology of SHSPU was further demonstrated using small angle X-ray scattering (SAXS), which showed a featureless X-ray scattering profile. In contrast, SAXS profiles of SSSPU and noncharged PU demonstrated microphase-separated morphologies. Moreover, SSSPU also displayed a broad ionomer peak ranging in q = 1–2 nm−1, which resulted from the sodium sulfonate ion pair association in the polar PEG soft phase. Morphologies of sulfonated polyurethanes correlated well with thermal and mechanical properties. [Copyright &y& Elsevier]