Ring-retaining polymerisation

It should also be noted that exocyclic olefins, the most representative of which are exomethylenecycloalkanes, can be homopolymerised by a ringopening reaction. 

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Commercially available polymers, produced from cycloolefins by ring-retaining polymerisation and ring-opening metathesis polymerisation of cycloolefins, and their typical uses are listed in Table 6.1 [12,14,144-147, 150,167-171,177-186],... 

Give the structure and stereochemical designation of all possible cycloolefin polymers that might, in principle, be obtained by stereospecific ring-retaining polymerisation. 

Explain why ring-retaining polymerisation of cyclopentene with a zirconocene catalyst yields poly(l,3-cyclopentylene) but not poly (1,2-cyclopentylene). 

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