Stereoisomerism of Conjugated Diene Polymers

Isomerism in conjugated diene polymers is a considerably more complex phenomenon than that encountered in a-olefin polymers. 

3-Butadiene and symmetric internally disubstituted butadienes (of the CH2=CR-CR=CH2 type) can give polymers containing 1,4 or 1,2 monomeric 

Stereoisomerism of polymers derived from 1,3-pentadiene and other unsymmetric terminally monosubstituted butadienes (CH2 = CH CH = CHR) is more complex. Stereoregular polymers can be formed from these monomers via their 

2- or 3,4-concatenation each polymer contains two sites of stereoisomerism in the monomeric unit  

The monomeric units formed via 1,4-polymerisation of monomers of the CH2=CH-CH=CHR type display stereoisomerism at the double bond (cis trans) and at the tertiary carbon atom which can assume two opposite configurations. Hence, the obtained 1,4-polymers can appear as cis- 1,4-isotactic, cis- 

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