Synthesis and Study of the Properties of Stereocontrolled Poly(N-isopropylacrylamide) Gel and Its Linear Homopolymer Prepared in the Presence of a Y(OTf)3 Lewis Acid: Effect of the C

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• 作者：Chandra Sekhar Biswas ; Niraj Kumar Vishwakarma ; Vijay Kumar Patel ; Avnish Kumar Mishra ; Satyen Saha ; Biswajit Ray
• 刊名：Langmuir
• 出版年：2012
• 出版时间：May 1, 2012
• 年：2012
• 卷：28
• 期：17
• 页码：7014-7022
• 全文大小：515K
• 年卷期：v.28,no.17(May 1, 2012)
• ISSN：1520-5827

文摘

Poly(N-isopropylacrylamide) (PNIPAM) hydrogels and the corresponding linear homopolymers were synthesized in different methanol鈥搘ater mixtures (x_m = 0, 0.13, 0.21, 0.31, 0.43, 0.57, and 0.76, where x_m is the mole fraction of methanol) in the presence of 0.1 M Y(OTf)₃ Lewis acid. The isotacticity (meso dyad (m), %) and cloud-point temperature of these homopolymers were gradually increased and decreased, respectively, with the increase in the x_m values of the synthesis solvent mixtures. Moreover, the corresponding linear PNIPAM homopolymers prepared in the absence of Y(OTf)₃ showed an almost constant isotacticity of m = 45% and a cloud-point temperature of 33.0 掳C. A SEM study revealed that the resulting hydrogels were highly porous except for the gels prepared at x_m = 0 and 0.76. The swelling ratios of these hydrogels in water at different temperatures and in different methanol鈥搘ater mixtures at 20 掳C and the deswelling rate and the reswelling rate of these hydrogels were studied. All of these swelling results were compared with that of the corresponding gels prepared in the absence of a Lewis acid (Biswas, C. S.; Patel, V. K.; Vishwakarma, N. K.; Mishra, A. K.; Bhimireddi, R.; Rai, R.; Ray, B. J. Appl. Polym. Sci.2012, DOI: 10.1002/app.36318) and explained on the basis of the porosity of the gel, the state of aggregation and isotacticity of the PNIPAM chain segment, and the cononsolvency of the methanol鈥搘ater mixture toward the PNIPAM chain segment.