Stereochemical Aspects of Polymerisation

Cycloolefins can be ring-open polymerised with a high degree of stereospecificity. Many poly(l-alkenylene)s prepared by metathesis polymerisation of cycloolefins are stereoregular polymers with presumably a cis or Irons configur- 

General schemes accounting for the changes in polymer structure that are brought about by changes in the structure of the catalyst have been proposed. The kind of transition metal, its oxidation state and the ligand environment of the metal are decisive for determination of the steric control in the propagation steps [121]. 

If it is supposed that the metal centre is chiral, then each of the Ph and Pt propagating species may appear in two enantiomorphic forms, A and A (the assumption is that the configuration of active sites Ph(h) and P ) or Pt( and 

Pt(/i) remains intact between successive propagation steps, i.e. there is no ligand migration or rotation about the Mt=C bond) [121]  

Let us also note that 1-methylnorbornene exists in two enantiomeric forms, R and S  

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