Abstract:

The polystyrene(PSt) was synthesized by a single electron transfer living radical polymerization(SET-LRP) in a binary mixture of dimethyl sulfoxide(DMSO) and water using 2,2-dibromomethyl-1,3-dibromopropane as the multifunctional initiator, Cu0 powder and tris-(2-dimethylamino ethyl)amine (Me6-TREN) as catalytic system. The resulting polymers were analyzed by 1H NMR and GPC, the results showed that the distribution of the resulting polymer was narrow(Mw/Mn=1.20, MGPCn=25.3×103, 42.6% conversion) and the polymers prepared were star shape and had perfect chain ends —Br retention. In addition, the kinetic plots of polymerization were first order, which indicated a living polymerization process. The various factors which had affected the SET-LRP of St such as solvent, polymerization temperature and phase transfer catalyst(PTC) were studied, and the results showed that the H2O content in the binary mixtures increasing form 10% to 20%(volume fraction) led to a reduction in polymerization rate, which could be revealed by the apparent polymerization rate constant(kappp) of 0.019 7 h-1 reducing from 0.026 4 h-1. Meanwhile the kappp increased in according with enhancing the polymerization temperature, increasing the amount of catalyst or adding the PTC. The addition of PTC or increasing the amount of catalyst could improve the control of the polymerization.

Key words: single electron transfer living radical polymerization, polystyrene, phase transfer catalyst, star polymer