Monomers containing a fused cyclobutene ring

The order of stability of the polymers is 5P 7P 6P 9P ss lOP IIP. The last two are quite stable at room temperature and must be heated to 100-200°C to effect their conversion to polyacetylene. Polymers made using WCVMe4Sn as catalyst (MW 40 000) contain comparable proportions of cis and trans double bonds (Edwards 1984). Polymer 8P, unlike 6P, is quite stable because the retro-Diels-Alder reaction is less favoured (it would give a cyclohexadiene, not a benzene derivative). Polymers of 8 having various cis contents (6-77%) have been prepared, but no information is available concerning their tacticity (Feast 1987). 

It should be noted that monomers that contain (i) a cyclobutene ring substituted at the olefinic carbons by COOMe or CF3, and (ii) a norbomene ring system, undergo ROMP by preferential opening of the norbomene ring (see Section 13.3.5) (Saimders 1995). 

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