Metathesis copolymerization of norbornene with phenylacetylene and its ring-substituted derivatives catalysed by WCl 6: 2. Reactivity of monomers

Abstract

Effects of ring substituents of phenylacetylene (PA) were studied in the metathesis copolymerization of norbornene (NBE) with PA catalysed by WCl 6. The shape of copolymer composition curves indicated the formation of random copolymers in the copolymerizations of NBE with PA and its para- or meta-substituted derivatives. The more electron-withdrawing the substituent, the less reactive the PA; the Hammett plot of these systems gave a straight line with a negative slope ( ϱ = −1.1). In contrast, some composition curves for the copolymerizations of NBE with ortho-substituted PAs were sigmoidal. This difference is explained in terms of the steric hindrance of ortho-substituents, i.e. the propagation reaction between the ortho-substituted PA end and the NBE monomer seems sterically difficult.