The micellization behavior of a series of multiblock copolymers ［poly(4-vinylpyridine)-b-polystyrene-b-poly(4-vinylpyridine)］n (P4VP-b-PS-b-P4VP)n in selective solvents

namely toluene and acidic water with pH3

was investigated by using transmission electron microscopy (TEM) and atomic force microscopy (AFM).Three multiblock copolymers (P4VP-b-PS-b-P4VP)n were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization with a cyclictri-thiocarbonate as chain transfer agent. The multiblock copolymers were relatively polydisperse with polydispersity indexes of ca. 1.74～2.19.The effects of block length

polymer concentration and selective solvent on the morphology of the multiblock copolymer micelle were discussed. Because P4VP blocks have longer length than that of PS blocks and can not dissolved in toluene

the (P4VP-b-PS-b-P4VP)n multiblock copolymers showed rich micellar morphologies in toluene.The experimental results indicated that the morphology of multiblock copolymer micelle in toluene changed from worm-like shape to shortrod and finally to spherical micelle as the length of P4VP block increased. The polymer concentration was found to have strong effects on the micelle morphology due to the special sequence structure of the multiblock copolymer.At low concentration

the multiblock copolymer tended to form spherical micelle in toluene. The polydispersity of molecular weight also affected the micelle morphology of the multiblock copolymer. For acidic water with pH3

a selective solvent for the P4VP blocks

all of the multiblock copolymers studied here formed spherical micelles in it due to the longer block length of P4VP blocks.