Temperature sensitive random linear and crosslinked copolymers of N-tert-butylacrylamide (NTBA) and acrylamide (Am) were synthesized by the solution polymerization method, using regulated dosing of comonomer Am having a higher reactivity ratio (r Am ϭ 1.5) than NTBA (r NTBA ϭ 0.5). Copolymers with varying feed ratios of NTBA and Am (80 : 20 to 20 : 80 mol %) were synthesized and characterized. For the synthesis of copolymer hydrogels, NЈ, N-methylene bisacrylamide (MBA) (1.13 mol %) was used along with monomers. The effect of composition on transition properties was evaluated for the linear copolymers and their hydrogels. A definite trend was observed. The incorporation of a higher percentage of the hydrophilic comonomer Am in the structure resulted in the shifting of the transition temperature towards a higher value. The transition temperatures of the copolymers synthesized with feed compositions of 80 : 20, 70 : 30, 60 : 40, 50 : 50, 40 : 60, 30 : 70, and 20 : 80 mol % were found to be 2, 10, 19, 27, 37, 45, and 58°C, respectively. Differential scanning calorimetry (DSC) studies confirmed the formation of random copolymers. The copolymers synthesized with a monomer feed ratio of 50 : 50 with regulated dosing showed a single glass transition temperature (T g ) at 168°C, while the copolymer synthesized with full dosing of Am at the beginning of the reaction showed two T g s, at 134 and 189°C. The copolymer samples were analyzed by Fourier transform infrared spectroscopy (FTIR) for ascertaining the composition. The composition of the copolymers followed the trend of the feed ratio, but the incorporation of NTBA in the copolymers was found to be lower than the feed ratio because of lower than quantitative yields of the reactions.

Breathable coatings based on polyacrylamide on cotton fabrics have been developed. The coatings show high water vapor permeability, while providing desirable protection against air and liquid water-penetration. These polyacrylamide based coatings were obtained by coating the fabric with polyacrylamide solution (4%), containing citric acid as a crosslinker (5–50 mol%), and sodium hypophosphite (0.3%) as a catalyst, followed by drying at 90 C and curing at 150 C. The curing reaction leads to formation of crosslinks among the polymer chains as well as between the polymer and the cotton fabric. The integrity of the crosslinked polyacrylamide coating was observed to be good. The resistance, to hydrostatic head for double and triple-coated samples, with cross-linker concentration of 50 and 20 mol% was found to be in the range of 800–1280 mm, while the air-permeability values reduced drastically by two orders of magnitude, compared to the control fabric. The water vapor transmission rate (WVTR) values for these samples were found to be excellent with only 5–23% reduction compared to the values shown by control cotton fabric. The mechanism of the reaction leading to the formation of crosslinks has been evaluated using FTIR and NMR spectroscopy.

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Smart breathable cotton fabrics were made using a temperature-sensitive copolymer - poly( N-tert-butylacrylamide- ran-acrylamide:: 27: 73). The cotton fabric was coated using an aqueous solution (20 wt%) of the copolymer containing 1,2,3,4-butanetetracarboxylic acid as a cross-linker (50 mol%) and sodium hypophosphite (0.5 wt%) as a catalyst, followed by drying (120°C, 5 min) and curing (200°C, 5 min). The integrity of the cross-linked coatings to the fabric was observed to be excellent. The coatings after integration to the cotton substrate retained temperature-sensitive swelling behavior and showed a transition in the temperature range of 15-40°C. Below 15°C, the coatings swell by 800% while above 40°C they deswell to a swelling percentage of less than 50% (on the basis of dry weight). The transition to swelling was completed in about 20 min while deswelling was quicker in 2-3 min. The response was found to be reversible and stable to repeated cycles of transition. The coated fabrics showed a temperature-responsive water vapor transmission rate (WVTR). The WVTR values of the responsive (copolymer coated) and the nonresponsive (poly(acrylamide) coated) breathable fabric were measured as a percentage (transmission percentage) of control uncoated substrate. The transmission percentage at 20% relative humidity for the copolymer coated fabrics was found to change across the transition temperature (15-45°C) from 58 to 94% compared to the poly(acrylamide)-coated fabrics which changed only from 70 to 94%, showing a clear response to changing environmental temperature.

Polyesters such as polyethylene terephthalate are widely used in textile fibers, films, and packaging of food and beverages. Originally driven by environmental reasons, recycling of postconsumer polyester bottles into textile fibers is now becoming commercially attractive. We studied the chemical recycling wherein part of the virgin raw-materials during preparation of polyester was replaced by washed post consumer polyester. During the process, the postconsumer polyester undergoes partial depolymerization before repolymerization. Role of reactoragitator configuration in achieving the solid-slurry and solid-melt mixing, and in depolymerization, was studied. Finally, suitability of the polymer for melt spinning and drawing of polymer into yarn was examined. V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: [520][521][522][523][524][525] 2012