A series of monomers (methacryle

acrylate and styrene)were polymerized by controlled／living radical polymerization in bulk using Reversible Addition-Fragmentation chain transfer (RAFT process)．A detail purification process of chain transfer agent (CTA) dithioesters (2-phenylprop-2-yl dithiobenzoate and 1-phenylethyl dithiobenzoate) was described．Results of styrene (St)

methyl methacrylate(MMA)

ethyl methacrylate(EMA)

butyl methacrylate (BMA)

octyl methaerylate (OMA)

methyl acrylate (MA)

ethyl acrylate (EA) polymerization using the AIBN／CTA(mole ratio 1：4) initiating system at 70～100℃ confirmed the living polymerization characteristics Diblock copolymers(PMMA-PEMA

PEMA—PMMA．PBMA-PMA

PBMA PEA

PSt-PBA) with well defined structures as well as controlled and narrow molar mass distribution were obtained from the lower．mass macroinitiator．The living character of the RAFT processisindicated bythe narrow polydispersity product(1．1～1．3)

alinearmolecularweight-conversion profile

the predictability of the molecular weight from the ratio of monomer consumed to transfer agent and the ability to produce block copolymer by further monomer addition．In each reaction step．the effects of conversion and reaction time on the molar mass characteristics of the prepared block copolymers were investigated．The SEC curves shift toward lower elution volumes as the reaction time increases While the polydispersity remained low and there was no detectable amount of unreacted starting maeroinitiator block as analyzed by GPC．When highmolecularweight startingmacroinitiator (Mn>30000) was used

therewas a substantiallow molecular weight shoulder observed．