The mdecular weight of high 1

2-content polybutatienes obtained with Mo-catalyst system decreased with the amount of allyl bromide added．The vinyl content and the syndio-tafic configuration of the polybutadienes also increased with the addition of allyl bromode．On account of the increase in both vinvl content and syndiotacticity the glass transition temperature of the polymer is raised and the polymer becomes partially crystalline and shows a higher yield strength．With or without addition of allyl bromide，the plots of yield strenght against [n] show linear relation．The two lines are paralled to each other．The molecular weight effects the extruding properties of the polymer，whereas the molecular weight distribution exerts only a minor effect under our experimental conditions．The phy-sicomechanical properties of the valcanized rubber ate nearly equivalent to that of cis-1，4-polybutadiene．