Polystyrene (PS) was obtained by reversible addition-fragmentation chain transfer (RAFT) polymerization

using benzyl dithiobenzoate

(PhC(S) SCHPh)

as transfer agent

AIBN as initiator．A amphiphilic copolymer

P(styrene-b-4-vinyl pyridine)(PS-b-P4VP) was prepared by using PS as macro-chain transfer agent and AIBN as initiator via the RAFT mechartism．Its strdcture was obtained by 1H-NMR analysis The conversion can reach almost 95％ within 24 h．Its structure was characterized by 1H-NMR studies The results showed that the molecular weight of the copolymer increased lineady with the increasing of conversion

and the living nature of the polymerization was revealed Self-assembly of this amphiphilic block eopolymer in different selective solvents was also studied by using transmission electron microscopy (TEM) and scanning electron microscopy(SEM)．The results showed that core shell microspheres were formed with P4VP block as the core and PS block as the shell in the nitrobenzene/THF solvent．The size of particles increased with the increasing of the concentration of the block copolymer．The size and shape of the panicles were also changed with the type of the solvent and concentration．