Differences in pressure and temperature transitions of proteins and polymer gels
TL;DR: Changes in some characteristic parameters in the time-intensity correlation functions of dynamic light-scattering measurement of aqueous solutions of pNIPAM at various pressures and temperatures showed no essential differences during temperature and pressure scanning and, as a whole, the motions of polymers in aQueous solutions were similar in two types of transitions until chain shrinkage occurred.
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Abstract: Pressure-driven and temperature-driven transitions of two thermoresponsive polymers, poly(N-isopropylacrylamide) (pNIPAM) and poly(N-vinylisobutyramide) (pNVIBA)), in both a soluble linear polymer form and a cross-linked hydro-gel form, were examined by a dynamic light-scattering method and direct microscopic observation, respectively. Their behavior was compared with that of protein systems. Changes in some characteristic parameters in the time-intensity correlation functions of dynamic light-scattering measurement of aqueous solutions of pNIPAM at various pressures and temperatures showed no essential differences during temperature and pressure scanning and, as a whole, the motions of polymers in aqueous solutions were similar in two types of transitions until chain shrinkage occurred. The gels (cross-linked polymer gels) prepared from the thermoresponsive polymers also showed similar volume transitions responding to the pressure and temperature increase. In temperature transitions, however, gels showed drastic volume shrinkage with loss of transparency, while pressure-induced transition showed a slow recovery of transparency while keeping the size, after first transient drastic volume shrinkage with loss of transparency. At a temperature slightly higher than the transition under atmospheric temperature, so-called reentry of the volume change and recovery of the transparency were observed during the pressure-increasing process, which implies much smaller aggregation or non-aggregated collapsed polymer chains in the gel at higher pressures, indicating a certain mechanistic difference of the dehydration processes induced by temperature and pressure.
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Citations
Influence of pressure on the state of poly(N-isopropylacrylamide) and poly(N,N-diethylacrylamide) derived polymers in aqueous solution as probed by FTIR-spectroscopy
TL;DR: In this article, the authors investigated the hydration and swelling properties of poly(N-isopropylacrylamide)-poly(N,N-diethylacRYlamide) derived microgels by Fourier transform infrared- (FTIR-) spectroscopy in a wide region of the temperature-pressure plane.
Conformational changes upon high pressure induced hydration of poly(N-isopropylacrylamide) microgels
Sebastian Grobelny,Christian Hofmann,Mirko Erlkamp,Felix A. Plamper,Walter Richtering,Roland Winter +5 more
TL;DR: In this paper, the authors investigated thermosensitive poly(N-isopropylacrylamide) microgels by high-pressure small angle X-ray scattering and Fourier transform infrared spectroscopy below and above the collapse temperature.
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