Preparation, Characterization of Cyclic Block Copolymers and Their Bulk Structures

合成了三种不同组成的聚苯乙烯-嵌段-聚异戊二烯-嵌段-聚苯乙烯共聚物，并通过同一分子上两个端基之间的偶联反应进行环化。通过GPC分馏从偶联产物中分离出环状聚苯乙烯-嵌段聚异戊二烯。它们被臭氧化，以分解聚异戊二烯嵌段选择性地涉及线性分子。从臭氧分解得到的分解产物的GPC分析，定量地证实了分馏产物包括c.a. 90%的环分子。结果表明，环状嵌段共聚物的形态转变与线性三嵌段共聚物的形态转变基本相同，而SI环状嵌段共聚物的微区间距均小于相应的SIS线性三嵌段共聚物，这归因于环状链构象。

Three polystyrene-block-polyisoprene-block-polystyrenes with different compositions were prepared and cyclized by the coupling reaction between two end groups on the same molecules. Ring-shaped polystyrene-block-polyisoprenes were isolated from the coupling products by GPC fractionation. They were ozonized so as to decompose the polylyisoprene blocks selectively referring to the linear molecule. From GPC analysis of the decomposed products obtained by ozonolysis, it was quantitatively confirmed that the fractionated products include c.a. 90% ring molecules. It has been found that the morphological transition of the ring-shaped block copolymers takes place depending on composition in essentially the same manner as that of the linear triblock copolymers, whereas the domain spacings of SI ring-shaped block copolymers were all smaller than those of the corresponding SIS linear triblock copolymers, which is attributed to looped chain conformation.