Specific preparation of diolefin homopolymers with equimolecular binary microstructures

During an investigation of some structural features in the stereospecific polymerization of conjugated diolefins evidence was obtained that some catalytic species are able to yield high molecular weight polymers containing selectively two of the several possible geometric isomers; moreover, the two isomers involved are present in equimolecular amounts, in a nonsequential arrangement. Up to now equimolecular (cis‐1,4‐3,4)‐polyisoprene, (1,2‐3,4)‐polyisoprene, and (cis‐1,4‐trans‐1,4)‐polybutadiene were obtained with different catalytic systems (among which, monometallic complexes). The preliminary results suggest an alternating propagation mechanism, similar to the one already proposed by several authors for Ziegler‐type catalysts. Further work is in progress to prepare new binary polymers of this type, with different microstructures.