Search

Bisphenol-A glycidyl ether epoxy resin was modified using reactive poly(ethylene glycol) (PEO). Dynamic mechanical analysis showed that introducing PEO chains into the structure of the epoxy resin increased the mobility of the molecular segments of the epoxy network. Impact strength was improved with the addition of PEO at both room (RT) and cryogenic (CT, 77 K) temperature. The curing kinetics of the modified epoxy resin with polyoxypropylene diamines was examined by differential scanning calorimetry (DSC). Curing kinetic parameters were determined from nonisothermal DSC curves. Kinetic analysis suggested that the two-parameter autocatalytic model suitably describes the kinetics of the curing reaction. Increasing the reactive PEO content decreased the heat flow of curing with little effect on activation energy (Ea), pre-exponential factor (A), or reaction order (m and n). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

The key requirements for a membrane in polymer electrolyte membrane fuel cells are a high ion conductivity, mechanical strength, and barrier properties. We reported earlier on two new promising hyperbranched polymers: poly(benzimidazole-co-aniline) (PBIANI), with a uniform rectangular net structure, and poly(benzimidazole-co-benzene) (PBIB), with a honeycomb structure. Both polymers exhibit a high ion conductivity and mechanical strength and have proven themselves suitable for the membranes of high-temperature polymer electrolyte membrane fuel cells. In this article, we deal with the determination of crystal structure and free-volume cell/microvoid size of these two polymers. Both PBIANI and PBIB had the same d-spacing (3.5 angstrom). However, the percentage of crystallinity was higher and the crystallite size was larger for PBIB. The kinetic diameters of hydrogen (2.89 angstrom), oxygen (3.46 angstrom), water (2.60 angstrom), and methanol (similar to 4.00 angstrom) were much larger than the free-volume cell/microvoid diameters of PBIANI (1.81 angstrom) and PBIB (1.96 angstrom) but much smaller than those of Nafion 115 (6.54 angstrom) and polybenzimidazole (PBI) (similar to 6.00 angstrom). The very small free-volume sizes of PBIANI and PBIB ensured good barrier properties against hydrogen, oxygen, water, and methanol, unlike those of Nafion-and PBI-type membranes. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 923-929, 2011

Lipase-catalyzed direct polycondensation of L-malic acid (L-MA), adipic acid, and 1,8-octanediol in organic media was achieved using Novozym 435 as the biocatalyst. 1H-nuclear magnetic resonance spectroscopy indicated that the selectivity of Novozym 435 was unaffected by changes in the organic media. The molecular weight (Mw) of the copolymers was affected by the L-MA feed ratio in the diacids, hydrophobicity of the solvent, and solubility of the substrates in the solvents. The Mw reached a maximum of 17.4 kDa at 80°C in isooctane at a L-MA feed ratio in the diacids of 40 mol %. The Mw increased from 3.2 to 16.6 kDa when the reaction time was extended from 6 to 48 hr at 70°C, and remained relatively constant with further increases in reaction time from 48 to 72 hr. The hydrophilicity, thermal stability, and crystallizability of the copolymer were also investigated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

A polyaniline (PANI) was synthesized by the oxidative polymerization using ammonium persulfate as an oxidizing agent. The PANI was then stirred with excess fuming sulfuric acid at room temperature for 6 h to obtain water soluble sulfonated polyaniline (SPANI). The degree of sulfonation was found to be 93–94% from the Fourier transform infrared (FTIR) and elemental analysis. The solubility of the SPANI in water was 1.25 g/L at room temperature and appeared as a green color solution. Conductivity of the PANI was decreased after sulfonation. A proliferation of hydrophilic nature of the PANI after sulfonation was observed from the water contact angle measurement. From the UV analysis, it was revealed that the energies required for the π–π* and bipolaron/polaron transitions are less and the intensity of these transitions are lower in SPANI compared to those of PANI. A detailed study on the crystal structures of PANI and SPANI were accomplished from the powder X-ray diffraction analysis. The SPANI exhibited a more ordered structure having a higher degree of crystallinity and crystallite sizes with an increased unit cell volume compared to the PANI. After sulfonation the morphology of PANI was transformed from a rod-like shape to a flat-plate shape. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Higher soluble nanostructured polyaniline was prepared by vapor-phase polymerization after passing aniline vapor through an aqueous acidic solution of ammo- nium persulfate (PANI-V). Polyaniline was also synthesized by the conventional oxidative polymerization method (PANI-C) in an aqueous medium for the comparison of its properties with PANI-V. PANI-V exhibited lower conductiv- ity but higher hydrophilicity and higher solubility (2-3 times) in different solvents, such as tetrahydrofuran, N- methyl-2-pyrrolidone, dimethylsulfoxide, N,N-dimethyl formamide, and m-cresol at room temperature compared with that of PANI-C. The thermal stability of PANI-V was higher than that of PANI-C. In-depth investigations of the crystal structures of PANI-C and PANI-V were performed through powder X-ray diffraction analysis. The PANI-V showed a less ordered structure with a lower crystallinity and crystallite size and with a higher d-spacing and inter- chain separation compared with PANI-C. The unit cell vol- ume of PANI-V was significantly higher with a greater number of atoms in the unit cell than that of PANI-C. V C 2009

Super adsorbent polyacrylamide (PAAm)/nanoclay (laponite, Lap) hydrogels were prepared by in situ free radical polymerization of AAm in an aqueous solution with clay as a crosslinker. The swelling properties and water-soluble cationic dye adsorption behaviors of the PAAm/laponite (PAAm/Lap) nanocomposite (NC) hydrogels were investigated. The parameters of swelling and diffusion of water in dye solutions were evaluated for the PAAm/Lap NC hydrogels. The adsorption behavior of the monovalent cationic dyes such as Basic Blue 12 (BB 12), Basic Blue 9 (BB 9), and Basic Violet 1 (BV 1), were studied on the NC hydrogels. The effects of the clay content of the hydrogel on its cationic dye uptake behavior were studied. The adsorption studies indicated that the rates of dye uptake by the NC hydrogels increased in the following order: BB 9 > BB 12 > BV 1. This order is similar to the swelling results of the PAAm/Lap NC hydrogel in the dye solutions. The equilibrium uptakes of the different dyes by the PAAm/Lap NC hydrogel were nearly the same. In the dye absorption studies, S-type adsorption in the Giles classification system was found for the BB 12 and BV 1 dyes, whereas L-type was observed for the BB 9 dye. After the heat treatment of PAAm/Lap, the rate of dye uptake and equilibrium dye uptake were increased. The NC hydrogels may be considered as a good candidate for environmental applications to retain more water and to remove dyes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

A series of sodium alginate (SA) and starch blends, namely 100/0, 90/10, 80/20, 70/30, and 60/40, were processed into films by solution casting process and the obtained SA/starch blends have been characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). DSC analysis shows single glass transition temperature (Tg) up to 30 wt % starch content in the blend, indicating the compatibility and interaction between SA and starch molecules. The TGA reveals the reduction in thermal stability of SA/starch with increase in starch content. FTIR analysis demonstrated the existence of specific intermolecular interactions between carbonyl groups of SA and hydroxyl groups of starch. The morphological analysis by SEM shows the homogeneous distribution of starch in the SA matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

The melting and crystallization behaviors of poly(trimethylene terephthalate) (PTT)/acrylonitrile-butadiene-styrene (ABS) blends were investigated with and without epoxy or styrene-butadiene-maleic anhydride copolymer (SBM) as a reactive compatibilizer. The existence of two separate composition-dependent glass-transition temperatures (T g 's) indicated that PTT was partially miscible with ABS over the entire composition range. The melting temperature of the PTT phase in the blends was also composition dependent and shifted to lower temperatures with increasing ABS content. Both the cold crystallization temperature and T g of the PTT phase moved to higher temperatures in the presence of compatibilizers, which indicated their compatibilization effects on the blends. A crystallization exotherm of the PTT phase was noticed for all of the PTT/ABS blends. The crystallization behaviors were completely different at low and high ABS contents. When ABS was 0-50 wt %, the crystallization process of PTT shifted slightly to higher temperatures as the ABS content was increased. When ABS was 60 wt % or greater, PTT showed fractionated crystallization. The effects of both the epoxy and SBM compatibilizers on the crystallization of PTT were content dependent. At a lower contents of 1-3 wt % epoxy or 1 wt % SBM, the crystallization was retarded, whereas at a higher content of 5 wt %, the crystallization was accelerated. The crystallization kinetics were analyzed with a modified Avrami equation.

Polyaniline/carboxylated multi-walled carbon nanotube (PAni/c-MWNT) nanocomposites have been synthesized by micellar aided emulsion polymerization with various c-MWNTs compositions, viz., 0.5, 1, 5, and 10 wt %. The microcrystalline parameters such as the nanocrystal size (〈N〉), lattice strain (g), interplanar distance (dhkl), width of the crystallite size distribution, surface weighted crystal size (Ds), and volume of the ordered regions were calculated from the X-ray data by using two mathematical models, namely the Exponential distribution and Reinhold distribution methods. The effects of heat ageing on the microcrystalline parameters of the PAni/c-MWNT nanocomposites were also studied and the results are correlated. The thermal stability and electrical resistivity of the PAni/c-MWNT nanocomposites were examined with thermogravimetric analysis (TGA) and a conventional two-probe method. The TGA data indicate that the thermal stability of the nanocomposites improved after the incorporation of c-MWNTs. The influence of temperature on the resistivity of the nanocomposites was also measured. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008

Different types of ultrathin multilayer composite membranes adsorbed on polyethylene terephthalate (PET) substrates are fabricated by the layer-by-layer (LBL) self-assembly technique. The hydrogen gas barrier performances of these membranes are meas- ured using a pressure permeation instrument. Polyethylenimines/graphene oxide (PEI/GO) are chosen as the optimal system; the mul- tilayer film reduces the hydrogen transmission rate of the uncoated PET film from 1357 to 24 cm 3 /(m 2 24 h 0.1 MPa). The membrane assembly process for the PEI/GO system is analyzed with UV-Visible spectroscopy, and the flat morphology of the ultra- thin film is observed by scanning electron and atomic force microscopies. Moreover, in order to fully characterize the PEI/GO multi- layer film system, we investigate the effects of multiple variables on the hydrogen resistance performance. These include the molecular weight of PEI, concentrations of PEI and GO, number of bilayers, soaking time, and drying methods. The film thickness is found to increase linearly during the LBL assembly process. V C 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41973.