期刊
VIBRATIONAL SPECTROSCOPY
卷 51, 期 1, 页码 44-51出版社
ELSEVIER
DOI: 10.1016/j.vibspec.2008.10.003
关键词
Poly(N-isopropylacrylamide); Poly(N-isopropylmethacrylamide); FTIR; Raman spectroscopy; Phase transition; DFT
资金
- Grant Agency of the Czech Republic [203/05/0425]
- Academy of Sciences of the Czech Republic [T400500402]
Temperature-induced phase transition in water solutions of poly(N-isopropylacrylamide) (PNIPAM) and poly(N-isopropylmethacrylamide) (PNIPMAM) have been studied by ATR FTIR and Raman spectroscopy in combination with quantum chemical calculations. The presence or absence of the alpha-methyl group has a strong effect on the physical structure of water solutions. Although the hydrophobic interactions for PNIPMAM and PNIPAM are very similar, PNIPMAM with additional methyl group exhibits significantly weaker intermolecular interactions between the amide groups. That effect is the cause of the higher transition temperature T-t by about 8 degrees C for PNIPMAM compared to PNIPAM due to the formation of larger compact structures. The presence of the methyl group is significant for the reversibility of the temperature transition during the backward cooling as the dissolution of more stable compact PNIPMAM requires overcoming of a higher energy barrier and shows a strong hysteresis. (C) 2008 Elsevier B.V. All rights reserved.
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