Stereoregular di-block butadiene/isoprene and butadiene/myrcene copolymers by iron catalysis

The catalytic systems obtained by combining monoalkyl-N-aryl-substituted iminopyridine iron complexes with methylaluminoxane are able to polymerize 1,3 conjugated dienes exhibiting high catalytic activity and selectivity. In particular, the complex (I) provides a polymer with an essentially 1,2-syndiotactic structure from butadiene, while polymers with a predominantly alternating cis-1,4/3,4 structure are obtained from isoprene and myrcene. Notably, these polymers also contain cis-1,4 unit sequences of various lengths: three units in polyisoprene and five units in polymyrcene. This system was also found to have living features, therefore, also taking advantage of the different selectivity exhibited towards different monomers, we were able to prepare stereo-block butadiene/isoprene and butadiene/myrcene copolymers constituted by the junction of two blocks, one crystalline/crystallizable and the other amorphous, with elastomeric and thermoplastic features within the same polymer chain. These stereo-block copolymers were found to be overall amorphous in the undeformed state, with excellent mechanical properties of ductility and elasticity, probably associated with the crystallization under stretching of the polybutadiene 1,2 blocks, such as to allow an expansion of the field of application of diene-based polymeric materials, currently essentially confined to the production of tires.