用激基缔合物荧光研究聚苯乙烯-聚甲基丙烯酸甲酯嵌段共聚物在溶液中的分子构型

聚苯乙烯在溶液中的激基缔合物荧光被发现以来一直引起人们的兴趣 ^{1, 2]}. 聚苯乙烯激基缔合作用主要与处于基态的苯环层叠对的形成有密切关系. 其形成方式主要有(1)符合n= 3规则的相邻苯环间的相互作用.(2)主链上非相邻苯环间由于链段的卷曲而相互作用.(3)分属于不同主链上的苯环相互贯穿时的相互作用. 由于激基缔合作用是近程作用, 因此利用它研究聚合物线团在稀溶液的变化及由稀溶液到浓溶液的变化是十分有效的 ^3]. 嵌段聚合物在形成胶束时, 一种聚合物分子链段形成核, 在核内大分子链段相互缠结, 相互贯穿. 而另一种聚合物分子链段形成壳, 其链段较为舒展. 因此利用激基缔合物荧光技术研究分子链段在核内的变化也应是十分有效的. 本文研究聚苯乙烯-聚甲基丙烯酸甲酯嵌段共聚物体系。

Study on Molecular Configuration of Poly(Styrene b methyl methacrylate) in Solution by Excimer Fluorescence Technique

Excimer fluorescence was used to probe the change of fluorescence intensity ratio of excimer/monomer chromophore I_E/I_M of poly(S-b-MMA)with concentration in THF solution. Three concentration regions are recognized in the range studied with respect to the values of I_E/I_M. In region Ⅰ, the values of I_E/I_M are independent of the concentration of the solution. In region Ⅱ, the I_E/I_M values increase with the increase of concentration. In region Ⅲ, the values of I_E/I_M almost keep constant. This phenomenon is attributed to the shrinkage of polymer coils and the entanglement of polymer chains at high concentration. The formation of micelles of the block copolymer in THF solution on addition of acetone was also studied. The change of I_E/I_M values indicates that the PS chains act as core and the PMMA chains as the corona.