Branching and Other Minor Irregularities

Branching in poly(vinyl chloride) has been studied using C n.m.r. by reduction of C—Cl bonds to C—H(D) bonds with LiAlH4 or LiAlD to give polyethylene with short branches (—CHjCl) and also longer branches. Branches with —CH2CI end-groups have also been detected in the H spectra of poly(vinyl chloride) itself. Also in poly(vinyl chloride) H n.m.r. spectra, the structures 

Roggero, T. Salvatori, and A. Mazzei, European Polymer J., 1977,13, 77. 

In polybutadiene, a substituted cyclopentane structural unit has been identified for polymerization carried out at low concentration. It was suggested that this unit is due to an intramolecular cyclization involving a penultimate 1,2-unit. 

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