Trans-Butadiene-piperylene copolymers

The synthesis of transtactic structures is based on catalysts in which the transition metal belongs to the 3d block (Ti, Cr, V, Ni). Particular emphasis is devoted to the synthesis of trans butadiene/piperylene copolymers and to their blends with synthetic cis-l,4-polyisoprene, with the aim of increasing the "green strength" of the latter. 

Figure 16. Processibility and green strength of trans-butadiene-piperylene copolymers as a function of melting point and Mooney viscosity.

Tranv-1,4- and 1,2-polybutadiene can be hydrohalogenated under mild conditions with gaseous HCl. The same is true of copolymers of butadiene with piperylene and also of isotactic transAA-piperylene. The addition of HCl to the asymmetric double bond is trans for polypiperylene and occurs in a stereoselective way, judging from the NMR spectra. 

Marina et al. (1984) reported the effect of solvent nature on the copolymerization of butadiene with trans-piperylene. An aliphatic solvent (heptane) rather than an aromatic solvent (PhMe) ensured a high polymerization rate and favorable reactivity ratios, and gave a copolymer with a high content of ds-1,4 units. 

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