PREPARATION AND MORPHOLOGY OF STAR-SHAPED COPOLYMERS OF THE A(N)B(N) TYPE

Star-shaped copolymers of the A(n)B(n) type composed of polystyrenes a nd polyisoprenes were prepared by two-stage coupling reactions using 4 , 8, and 12-functional chlorosilane compounds as linking agents. At th e first stage, living polystyrenes end-capped with 1,1-diphenylethylen e were confirmed to react with half or less than half of the chlorines . At the second stage, living polyisoprenes end-capped with a few unit s of butadiene were used. The final products purified by GPC fractiona tion were confirmed to be star-shaped copolymers having the objective molecular structures by NMR and osmometry. A(n)B(n) Star-shaped copoly mers having arm-molecular weights of M-n similar to 1 x 10(4) showed c lear microphase-separated structure. In the samples having arm-molecul ar weights of M-n-4 x 10(4), however, diffusive domain boundaries were observed. This may be due to bicomponent multibranching and low mobil ity of arm polymers.