C-13 NMR-STUDY OF THE MICROSTRUCTURE OF POLYNORBORNADIENE

Polynorbornadiene obtained with an AlEtCl2/t-BuCl catalyst system at -50-degrees-C was successively fractionated by boiling toluene and o-dichlorobenzene, with the result that the boiling toluene soluble portion was the major fraction. The microstructures of both the toluene soluble and o-dichlorobenzene insoluble fractions were characterized by high resolution C-13 nuclear magnetic resonance spectroscopy in solution and or in the solid state and by differential scanning calorimetry. Both polymer fractions were shown to contain the repeating 3,5-disubstituted nortricyclene unit with exo exo and exo endo placements present in a 55:45 ratio. The polymerization mechanism involving the stereoregular addition of a norbornadiene monomer to the carbonium ion at the growing polymer chain-end was also proposed.