Molecule isotactic stereoisomerism

By enantioselective polymerization polymer chains, each containing only one configurational kind of monomeric unit, are produced from a mixture of stereoisomeric monomer molecules. The number of kinds of polymer chain generated therefore equals the number of various stereoisomers in the monomer mixture. In the course of propagation, the enantiomeric composition of the polymer and unreacted monomer remains identical to the intial composition. When optically active monosubstituted cyclic monomers are polymerized, stereoregular polymers are formed with both isotactic polyR and polyS chains... 

Stereoisomerism refers to molecular species that have the same composition and bond sequence but a different arrangement in space of their atoms. Stereoisomers that are characterized by different interatomic distances between certain atoms that are not bound directly are called diastereoisomers. Examples of diastereoisomers are cis-trans isomers of compounds containing C = C bonds and syn-anti isomers of compounds containing C = N bonds. Other diastereoisomers are not based on the presence of a double bond. For example, a molecule with more than one tetrahedral carbon that has different substituents may form diastereoisomers. For example, for a head-to-tail polymerized monosubstituted vinyl monomer, there are three possible structures indicated as isotactic, syndiotactic and atactic, which are schematically shown below ... 

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