Novel sulfonated poly(arylene ether ketone) copolymers bearing carboxylic or benzimidazole pendant groups for proton exchange membranes

A novel strategy in which the benzimidazole group and sulfonic group are simultaneously attached to an aromatic polymer has been reported in this paper. For this purpose, sulfonated poly(arylene ether ketone) copolymers containing carboxylic acid groups (SPAEK-x-COOH, x refers to the molar percentage Of sulfonated repeating units) are prepared by the aromatic nucleophilic polycondensation of sodium 5,5'-carbonyl-bis(2-fluobenzene-sulfonate) (SDFBP), 4,4'-difluorobenzophenone (DFBP) and phenolphthalin (PPL). Then the carboxylic acid groups attached to the SPAEK-x-COOH are transformed to benzimidazole units through condensation reactions (referred to as SPAEK-x-BI). Fourier transform infrared spectroscopy and H-1 NMR measurements are used to characterize and confirm the structures of these copolymers.

Synthesis and characterization of novel sulfonated poly(arylene ether ketone) copolymers with pendant carboxylic acid groups for proton exchange membranes

A series of novel side-chain-type sulfonated poly(arylene ether ketone)s with pendant carboxylic acid groups copolymers (C-SPAEKs) were synthesized by direct copolymerization of sodium 5,5'-carbonyl-bis(2-fluorobenzenesulfonate), 4,4'-difluorobenzophenone and 4,4'-bis(4-hydroxyphenyl) valeric acid (DPA). The expected structure of the sulfonated copolymers was confirmed by FT-IR and H-1 NMR. Membranes with good thermal and mechanical stability could be obtained by solvent cast process. It should be noted that the proton conductivity of these copolymers with high sulfonation degree (DS > 0.6) was higher than 0.03 S cm(-1) and increased with increasing temperature. At 80 degrees C, the conductivity of C-SPAEK-3 (DS = 0.6) and C-SPAEK-4 (DS = 0.8) reached up to 0.12 and 0.16 S cm-1, respectively, which were higher than that of Nafion 117 (0.10 S cm(-1)).

Thermo- and pH-sensitive poly(vinylmethyl ether)/carboxymethylchitosan hydrogels crosslinked using electron beam irradiation or using glutaraldehyde as a crosslinker

BACKGROUND: Stimuli-sensitive or intelligent hydrogels have been investigated for many biomedical and pharmaceutical applications. Those hydrogels with dual sensitivity will have more extensive potential applications. The aim of the work presented was to prepare a series of thermo- and pH-sensitive hydrogels based on poly(vinylmethyl ether) (PVME) and carboxymethylchitosan (CMCS). The hydrogels were crosslinked using electron beam irradiation (EB) or using glutaraldehyde (GA) as a crosslinker at room temperature.

Synthesis and Characterization of Hyperbranched Poly(ether amide)s with Thermoresponsive Property and Unexpected Strong Blue Photoluminescence

A facile and efficient strategy for the syntheses of novel hyperbranched poly(ether amide)s (HPEA) from multihydroxyl primary amines and (meth)acryloyl chloride has been developed. The chemical structures of the HPEAs were confirmed by IR and NMR spectra. Analyses of SEC (size exclusion chromatography) and viscosity characterizations revealed the highly branched structures of the polymers obtained. The resultant hyperbranched polymers contain abundant hydroxyl groups. The thermoresponsive property was obtained from in situ surface modification of abundant OH end groups with N-isopropylacrylamide (NIPAAm). The study oil temperature-dependent characteristics has revealed that NIPAAm-g-HPEA exhibits an adjustable lower critical solution temperature (LCST) of about 34-42 degrees C depending on the grafting degree. More interestingly, the work provided an interesting phenomenon where the HPEA backbones exhibited strong blue photoluminescence.

Rhythmic growth of ring-banded spherulites in blends of liquid crystalline methoxy-poly(aryl ether ketone) and poly(aryl ether ether ketone)

Rhythmic growth of ring-banded spherulites in blends of liquid crystalline methoxy-poly(aryl ether ketone) (M-PAEK) and poly(aryl ether ether ketone) (PEEK) has been investigated by means of differential scanning calorimetry (DSC), polarized light microscopy (PLM), and scanning electron microscopy (SEM) techniques. The measurements reveal that the formation of the rhythmically grown ring-banded spherulites in the M-PAEK/PEEK blends is strongly dependent on the blend composition. In the M.-PAEK-rich blends, upon cooling, an unusual ring-banded spherulite is formed, which is ascribed to structural discontinuity caused by a rhythmic radial growth. For the 50:50 M-PAEK/PEEK blend, ring-banded spherulites and individual PEEK spherulites coexist in the system. In the blends with PEEK as the predominant component, M-PAEK is rejected into the boundary of PEEK spherulites. The cooling rate and crystallization temperature have great effect on the phase behavior, especially the ring-banded spherulite formation in the blends. In addition, the effects of M-PAEK phase transition rate and phase separation rate on banded spherulite formation is discussed.

Crystallization behavior of poly(epsilon-caprolactone) in poly(epsilon-caprolactone) and poly(vinyl methyl ether) mixtures

The morphological development and crystallization behavior of poly(epsilon-caprolactone) (PCL) in miscible mixtures of PCL and poly(vinyl methyl ether) (PVME) were investigated by optical microscopy as a function of the mixture composition and crystallization temperature. The results indicated that the degree of crystallinity of PCL was independent of the mixture composition upon melt crystallization because the glass-transition temperatures of the mixtures were much lower than the crystallization temperature of PCL. The radii of the PCL spherulites increased linearly with time at crystallization temperatures ranging from 42 to 49 degrees C. The isothermal growth rates of PCL spherulites decreased with the amount of the amorphous PVME components in the mixtures. Accounting for the miscibility of PCL/PVME mixtures, the radial growth rates of PCL spherulites were well described by a kinetic equation involving the Flory-Huggins interaction parameter and the free energy for the nuclei formation in such a way that the theoretical calculations were in good agreement with the experimental data. From the analysis of the equilibrium melting point depression, the interaction energy density of the PVME/PCL system was calculated to be -3.95 J/cm(3).

Study on crystallization of poly(epsilon-caprolactone) in poly(epsilon-caprolactone)/poly(vinyl methyl ether) blends

The crystallization behaviors of poly( E-caprolactone) (PCL) in poly(epsilon-caprolactone) (PCL) and poly(vinyl methyl ether) (PVME) blends were investigated by POM, DSC, WAXD, SAXS. POM results indicated that spherical crystal morphology was present during isothermal process, and the spheric growth rates were reduced with increasing the contents of PVME in PCL/PVME blends. It was found that the crystallinity of PCL in the blends remained almost constant regardless of the blend composition, but it was dependent on preparation technique. Solution-crystallization was found to be a technique capable of increasing crystallinity levels for some compositions. The melting behavior of the blends is a rather complex process. Both solution-crystallized samples and isothermal-crystallized samples exhibited a single endotherm. Oppositely, melting-crystallized samples exhibited dual-melting endotherms whose mangnitudes vary with blend compositions. On the basis of WAXD and SAXS experiments, it is found that the crystal structure is unchanged, but the long period increases with increasing the content of PVME because of the thickening of the amorphous layers.

Assembly of 12-tungstosilicic acid and 4-aminobenzo-15-crown-5 ether based on the electrostatic attraction through bridging of oxonium ions on different substrates

Based on the electrostatic attraction Keggin-type polyoxometalate H4SiW12O40 (SiW12) and small molecule 4-aminobenzo-15-crown-5 ether (4-AB15C5) were alternately deposited on poly (allylamine hydrochloride) (PAH)-derived indium tin oxide (ITO) substrate through a layer-by-layer (LBL) self-assembly, forming a supramolecular multilayer film (film-A). SiW12 was also deposited on a glassy carbon electrode (GCE) derived by 4-AB15C5 via covalent bonding in 0.1 M NaCl aqueous solution and formed a composite monolayer film (film-B). UV-vis absorption spectroscopy, X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared (FTIR) spectroscopy measurements demonstrated that the interactions between SiW12 and 4-AB15C5 in both two film electrodes were the same and caused by the bridging action of oxonium ions. But, the nanostructure in the two film electrodes was different. 4-AB15C5 in film-A was oriented horizontally to ITO substrate, however, that in film-B was oriented vertically to GCE. Namely film-A corresponded to a layer structure, and film-B corresponded to an intercalation structure.

Synthesis, properties, and gas permeation performance of cardo poly(arylene ether sulfone)s containing phthalimide side groups

Novel bisphenol monomers (1a-d) containing phthalimide groups were synthesized by the reaction of phenolphthalein with ammonia, methylamine, aniline, and 4-tert-butylanilne, respectively. A series of cardo poly (arylene ether sulfone)s was synthesized via aromatic nucleophilic substitution of 1a-d with dichlorodiphenylsulfone, and characterized in terms of thermal, mechanical and gas transport properties to H-2, O-2, N-2, and CO2. The polymers showed high glass transition temperature in the range 230-296 degrees C, good solubility in polar solvents as well as excellent thermal stability with 5% weight loss above 410 degrees C. The most permeable membrane studied showed permeability coefficients of 1.78 barrers to O-2 and 13.80 barrers to CO2, with ideal selectivity. factors of 4.24 for O-2/N-2 pair and 28.75 for CO2/CH4 pair. Furthermore, the structure-property relationship among these cardo poly(arylene ether sulfone)s had been discussed on solubility, thermal stability, mechanical, and gas permeation properties. The results indicated that introducing 4-tert-butylphenyl group improved the gas permeability of polymers evidently.

Facile synthesis and characterization of hyperbranched poly(ether amide)s generated from Michael addition polymerization of in situ created AB(2) monomers

A new straightforward strategy for synthesis of novel hyperbranched poly (ether amide)s from readily available monomers has been developed. By optimizing the reaction conditions, the AB(2)-type monomers were formed dominantly during the initial reaction stage. Without any purification, the AB(2) intermediate was subjected to further polymerization in the presence (or absence) of an initiator, to prepare the hyperbranched polymer-bearing multihydroxyl end-groups. The influence of monomer, initiator, and solvent on polymerization and the molecular weight (MW) of the resultant polymers was studied thoroughly. The MALDI-TOF MS of the polymers indicated that the polymerization proceeded in the proposed way. Analyses of H-1 NMR and C-13 NMR spectra revealed the branched structures of the polymers obtained. These polymers exhibit high-moderate MWs and broad MW distributions determined by gel permeation chromatography (GPC) in combination with triple detectors, including refractive index, light scattering, and viscosity detectors. In addition, the examination of the solution behavior of these polymers showed that the values of intrinsic viscosity [eta] and the Mark-Houwink exponent a were remarkably lower compared with their linear analogs, because of their branched nature.

Nature of the ring-banded spherulites in blends of aromatic poly(ether ketone)s

The ring-banded spherulites in liquid crystalline poly(aryl ether ketone) (LC-PAEK) and poly(aryl ether ether ketone) (PEEK) blends with a higher content (>50%) of LC-PAEK are investigated by polarizing light microscopy (PLM) and atomic force microscopy (AFM) techniques. The results indicate that the light core and rings of the ring-banded spherulites under PLM are mainly composed of an LC-PAEK phase, while the dark rings consist of coexisting phases of PEEK and a small amount of LC-PAEK. The formation of the ring-banded spherulites is attributable to structural discontinuity caused by a rhythmic radial growth.

Ordering-induced micro-bands in thin films of a main-chain liquid crystalline chloro-poly(aryl ether ketone)

Micro-banded textures developed from thin films of a main-chain thermotropic liquid crystalline chloro-poly(aryl ether ketone) in the melt were investigated using transmission electron microscopy (TEM). selective area electron diffraction, and atomic force microscopy techniques. The micro-banded textures were formed in the copolymer thin films after annealing at temperatures between 320 and 330degreesC, where a highly ordered smectic crystalline phase is formed without mechanical shearing. The micro-banded textures displayed a sinusoidal-like periodicity with a spacing of 150 nm and an amplitude of 2 rim. The long axis of the banded texture was parallel to the b-axis of an orthorhombic unit cell. In the convex regions, the molecular chains exhibited a homeotropic alignment, i.e. the chain direction was parallel to the film normal. In the concave re-ions, the molecular chains possessed a tilted alignment. In addition to the effects of annealing temperatures and times, the thickness of the film played a vital role in the formation of the banded texture. A possible formation mechanism of this banded texture vas also suggested and discussed. It was suggested that the micro-bands were formed during cooling.

Microwave-assisted synthesis of high-molecular-weight poly(ether imide)s by phase-transfer catalysis

A facile and rapid polycondensation reaction of disodium bisphenol A with bis(chlorophthalimide)s was preformed with a domestic microwave oven in o-dichlorobenzene by phase-transfer catalysis. The polymerization reactions, in comparison with conventional heating polycondensation, proceeded rapidly and were completed within 25 min. The polymerizations gave the corresponding poly(ether imide)s with inherent viscosities of 0.55-0.92 dL g(-1). The effects of various factors on the polymerization, such as the amount of the catalyst, the reaction time, and the microwave power were studied. The properties of the polymers were briefly characterized.

Ordered macroporous films from self-assembly of two-armed polymer with a crown ether core

Highly ordered honeycomb-like macroporous films were obtained via self-assembly of a two-armed polymer with a crown ether core under controlled conditions. A possible mechanism is speculated, primarily based on the strong affinity between the crown ether cores. The pore size and arrangement are sensitive to the solvent evaporation rate and the solution concentration. Upon spontaneous drying, the pore diameter (D) depends on the concentration (c) by a relation of D=518c(-0.610).