Isotactic PCHE

The characterization of isotactic PCHE (/PCHE) has been shown to have two distinct crystalline forms. Form 1, originally reported from analysis of isotactic 

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Figure 23.1 13C NMR spectra of (a) syndiotactic PCHE from hydrogenation of sPS, (b) atactic PCHE from hydrogenation of PS, (c) isotactic PCHE from Ziegler-Natta polymerization of vinylcyclohexane and (d) isotactic PCHE from hydrogenation of /PS (Ref. 18)...

Attempts to perform the cationic polymerization of vinylcyclohexane have been reported. While coordination-type polymerization of vinylcyclohexane monomer gives isotactic PCHE, polymerization under conditions that lead to the formation of carbocationic intermediates leads to polymers with a differentiated backbone structure. Instead of propagating via the vinyl carbons, the cationic polymerization proceeds via hydride shift to a tertiary carbocation, which then propagates to provide the polymer shown in Scheme 23.3 [32]. Conditions for these polymerizations typically involved the use of aluminum halide catalysts in halogenated hydrocarbon solvents at low temperatures [32,38]. For the most part, molecular weights are relatively low. 

Figure 23.6 Depiction of the unit cell of isotactic PCHE Form 1 unit cell Reprinted with permission from Nishikawa etal., Macromolecules, 29, 5558. Copyright 1996 American Chemical Society...

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