Real‐time temperature and photon transmission measurements for monitoring phase separation during the formation of poly(N‐isopropylacrylamide) gels
Real‐time temperature and photon transmission measurements for monitoring phase separation during the formation of poly(N‐isopropylacrylamide) gels
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实时温度和光子传输测量，用于监测聚（N-异丙基丙烯酰胺）凝胶形成过程中的相分离
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发表时间：
2002
期刊：
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通讯作者：
Ö. Pekcan
中科院分区：
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作者：
S. Kara;O. Okay;Ö. Pekcan
使用实时光子传输和温度测量研究了聚（N-异丙基丙烯酰胺）（PNIPA）水凝胶形成过程中的相分离。该水凝胶是在 N,N'-亚甲基双丙烯酰胺 (BAAm) 作为交联剂的水溶液中，通过 N-异丙基丙烯酰胺 (NIPA) 的自由基交联聚合制备的。起始反应温度T0在20℃和28℃之间变化。诱导期后，所有凝胶化实验均导致放热反应。实验中观察到温度升高了 6.5 ± 0.6°C。结果表明，PNIPA 凝胶形成和生长过程中温度的升高伴随着透射光强度 Itr 的同时降低。在低于 PNIPA 下临界溶液温度的温度下 Itr 的降低可以通过凝胶网络不均匀性引起的浓度波动来解释。在较高温度下，凝胶系统通过旋节线分解过程经历相变。 © 2002 Wiley periodicals, Inc. J Appl Polym Sci 86: 3589–3595, 2002
Phase separation during the formation of poly(N-isopropylacrylamide) (PNIPA) hydrogels was investigated using real-time photon transmission and temperature measurements. The hydrogels were prepared by free-radical crosslinking polymerization of N-isopropylacrylamide (NIPA) in the presence of N,N′-methylenebisacrylamide (BAAm) as a crosslinker in an aqueous solution. The onset reaction temperature T0 was varied between 20 and 28°C. Following an induction period, all the gelation experiments resulted in exothermic reaction profiles. A temperature increase of 6.5 ± 0.6°C was observed in the experiments. It was shown that the temperature increase during the formation and growth process of PNIPA gels is accompanied by a simultaneous decrease in the transmitted light intensities Itr. The decrease in Itr at temperatures below the lower critical solution temperature of PNIPA was explained by the concentration fluctuations due to the inhomogeneity in the gel network. At higher temperatures, it was shown that the gel system undergoes a phase transition via a spinodal decomposition process. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3589–3595, 2002