Living free-radical polymerization in the presence of dithioesters
- 化学化工－已发表论文 
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 methacrylate (OMA), methyl acrylate (MA), ethyl acrylate (EA) polymerization using the AIBN/CTA (mole ratio 1:4) initiating system at 70 similar to 100 degreesC 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 process is indicated by the narrow polydispersity product (1.1 similar to 1.3), a linear molecular weight-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 macroinitiator block as analyzed by GPC. When high molecular weight starting macroinitiator ( M-n > 30000) was used, there was a substantial low molecular weight shoulder observed.