Vinyl Polymerization Promoted by VO(acac)2 - TEMPO Complexes

Vanadium (IV) oxyacetylacetonate or vanadium (IV) oxyacetylacetonate-2,2,6,6tetramethylpiperidinyl- 1-oxy (TEMPO) complexes activated with diethyl aluminium bromide as catalysts were employed for the polymerization of methyl methacrylate in benzene at 40°C. The catalysts were compared based on various parameters such as AIIV ratio, reaction time, catalyst, monomer concentration and temperature on the rate of polymerization and yield. The rate of polymerization increased linearly with increasing monomer concentration with first order dependence. Polymer yield was maximum when the AIIV ratios were 2.2 and 1.4 and the activation energies were 8.9 and 9.1 kcal.rno! , respectively for the catalysts VO(acach / AIEt2Br and VO(acach / AIEt2Br / TEMPO. Inclusion of TEMPO to the catalyst system VO(acach / AIEt2Br shows increased catalytic activity. The catalyst systems have resulted in syndiotactic rich PMMA s having Mn values in the range of 12000-23000. PMMA s of narrow molecular weight distributions in the range of 1.2-1.7 could be obtained under mild conditions in benzene solvent at 40°C.