The polymerization of isoprene by Ti(OBu)4 -AlEt2Cl and Ti(OBu)4 -AlEt3 catalysts to which AIX, was added has been investigated. In Ti(OBu)4 -AlEt2Cl-AlX3 catalysts, the maximum activity of ...polymerization is exhibited when AlEt2Cl/AlX3= 3 and total Al/Ti = 8 (represented as CAT I -X); and in Ti (OBu)4 -AlEt3 -Al X3 catalysts, when AlEt3/AlX3=1 and total Al/Ti = 7-8 (represented as CAT-II-X). By CAT-I -Br and CAT- II -Br, cis-1, 4-polymer with high molecular weight, η >4, is easily obtained. The rate equations in the case of both catalysts are of first order with respect to concentration of isoprene and the activation energies are from 8.7 to 12.0 kcal/mol. The number average molecular weight, Mn, of the polymers obtained by CAT I -Br and CAT-II -Br is larger and Mw /Mn value is smaller than those of the polymers obtained by CAT I -Cl and CAT II -Cl. Then, it was assumed that the less degree of chain transfer occurred in the polymerization by the catalysts which contained AlBr3.
PDF