A NEW MECHANISM FOR THE TRANSITION-METAL CATALYZED COPOLYMERIZATION OF CONJUGATED DIENES WITH OLEFINS - THE DOUBLE COORDINATION MECHANISM

We have focused our interest on the ethylene-butadiene copolymerizations catalyzed with Ziegler-Natta type catalysts. The catalysts used are MgCl2 supported titanium catalysts. The main features of these copolymerizations (stereospecificity of the butadiene enchainments, multiblock structure, gel formation) cannot be rationalized on the basis of the Cossee mechanism. We propose a new model: the double coordination mechanism. It explains all the phenomena observed. Experimental confirmations will be presented in this paper.