分子量对聚合物临界相转变温度的影响.pdf

4488 Macromolecules 1999, 32, Inverse Molecular Weight Dependence of Experimental Procedures. N-Isopropylacrylamide Cloud Points for Aqueous (NIPA) monomer provided by Kohjin Co., Japan, was Poly(N-isopropylacrylamide) Solutions recrystallized twice from a benzene/n-hexane mixture prior to use. The polymerization was conducted in tert- Zhen Tong,* Fang Zeng, and Xu Zheng butyl alcohol at 55 °C for 8 h with the monomer concentration of 1.073 mol/L and the initiator azobis- Research Institute of Materials Science, South China (isobutylonitrile) of 0.58 mol %. The obtained poly(N- University of Technology, Guangzhou 510641, China isopropylacrylamide) (PNIPAm) sample was purified by Takahiro Sato precipitation three times from acetone solution into n-hexane and then fractionated by phase separation in Department of Macromolecular Science, Osaka University, acetone/n-hexane mixtures at 30 °C several times. The Toyonaka, Osaka 560, Japan first fraction was produced at the volume fraction of Received January 19, 1999 n-hexane of 0.51 in the mixture, and the following Revised Manuscript Received April 19, 1999 fractions were obtained by adding n-hexane. Two frac- tions T-49 and T-101 were chosen to be used in this Introduction. Poly(N-isopropylacryla