Head-to-Head Polymers. XVI. Polymerization of 2,3-Dimethyibutadiene-l,3 to cis- and trans-1,4-Poly(2,3,-dimethyIbutadiene)

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Abstract
2,3-Dimethylbutadiene-1,3 was polymerized to cis- and trans-1,4-poly(2,3-dimethylbutadiene) of high stereochemical purity with triisobutylaluminum/titanium tetrachloride initiator systems in n-hexane. With a mole ratio of Al/Ti of 2:1, pure cis isomer was obtained while an Al/Ti ratio of 1:2 in the initiator system produced the trans polymer of 1,4-poly(2,3-dimethylbutadiene) free from 1,2-isomers. For the cis-isomer a 0.5 mol% initiator to monomer ratio gives maximum molecular weight while a 1 mol% ratio gives maximum yield. For the trans-polymer the ratios are 1 and 2 mol%, respectively. The cis- and trans-polymers are high melting crystalline materials of melting points of 190°C and near 280°C, respectively. The glass transition temperatures were 2 and 12°C, respectively (onset of transition). The temperature of maximum rate of degradation was 380°C for both polymers.