COPOLYMERIZATION OF STYRENE WITH BUTADIENE AND ISOPRENE USING A RARE-EARTH CATALYST

In the copolymerization of styrene-butadiene and styrene-isoprene, a n ovel rare earth catalyst system (CF3CO2)(3)Ln/R(3-n)AlH(n)/(CH3)(3)CCH 2Br (Ln = Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu ; R = Me-, Et-, i-Bu-, and Oct-; n = 0 and 1) has been studied. The 1, 4 unit contents in the copolymers obtained are found to range from 64 .4 to 99.6% with St contents of 5.2 to 59.9%, and intrinsic viscositie s of 0.1 to 0.5 dl g(-1) measured by i.r., H-1 n.m.r. and C-13 n.m.r. spectra. From the calculated data of linked ratios, a change in the mi crostructure is induced by the styrene unit, probably adjacent to the butadiene or isoprene unit. An interesting result is that the ratios o f styrene unit linked with 1, 2 or 3,4 units in the copolymers are far higher than in copolymers obtained with the nickel catalyst. The expe rimental results are discussed in terms of rare earth pi-allyl coordin ation and back-biting mechanism.