PNIPA和PDEA在水-甲醇混合溶剂中性质的研究

分别研究了聚N-异丙基丙烯酰胺（PNIPA）和聚N,N-二乙基丙烯酰胺（PDEA）在水-甲醇混合溶剂中的溶液性质.结果表明,在PDEA和PNIPA体系中均存在水和甲醇分子之间的复合.由于PDEA比PNIPA的亲脂性强,在水-甲醇混合溶剂中,水与甲醇分子形成的复合物对PDEA和PNIPA的溶剂化作用不同,导致随着体系中甲醇体积分数（φ）的增大,PNIPA体系的低临界溶解温度（TLCS）发生了再进入相转变,而PDEA体系的TLCS则逐渐升高.

A Study of Solution Properties of Poly(N-isopropylacrylamide) and Poly ( N,N-diethylacrylamide) in Mixed Solvent of Water-Methanol

The phase behaviors of Poly(N-isopropylacrylamide) (PNIPA) and Poly(N,N-diethylacrylamide) (PDEA) were investigated individually in mixed solvent of water-methanol using UV-Vis spectroscopy. The results show that the low critical solution temperature (TLCS) of PNIPA system undergoes reentrant change, while the TLCS of PDEA system shifts to higher temperature as the volume fraction of methanol (φ) increases. Refractive index measurement shows the formation of water-methanol complexes in PDEA system as well as in PNIPA system. To explain the different phase behavior of PDEA system from PNIPA, the conformational changes of PNIPA and PDEA molecular chains in mixed solvent of water-methanol were studied using the viscometry and Fourier Transform Infrared Spectroscopy. It was found that unlike the PNIPA, which underwent reentrant coil-to-globule-to-coil transition, the PDEA chains experienced homogeneous expansion-to-contraction-to-expansion as φ increased. It is believed that the different phase behavior of PDEA system from PNIPA is due to the more lipophilic property of PDEA structure than that of PNIPA, and consequently, the difference of solvating abilities of water-methanol complexes toward molecules PNIPA and PDEA.