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 40oC. The catalysts were compared based on various parameters such as Al/V 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 Al/V ratios were 2.2 and 1.4 and the activation energies were 8.9 and 9.1 kcal.mol-1, respectively for the catalysts VO(acac) 2 / AlEt 2 Br and VO(acac) 2 / AlEt 2 Br / TEMPO. Inclusion of TEMPO to the catalyst system VO(acac) 2 / AlEt 2 Br shows increased catalytic activity. The catalyst systems have resulted in syndiotactic rich PMMA’s having M n 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 40oC.