Configurational Statistics of Poly(cyclohexene carbonate)

Conformational characteristics of poly(cyclohexene carbonate) (PCHC) have been investigated via molecular orbital (MO) calculations and NMR experiments on model compounds. The MO energies established through comparison with the NMR experiments were applied to the rotational isomeric state scheme with Bernoulli and Markov stochastic processes to yield configurational properties such as unperturbed characteristic ratio, its temperature coefficient, configurational entropy, tacticity entropy, and coherence number of PCHC chains including various stereosequences. trans-PCHC composed of (R,R)- and/or (S,S)-repeating units prefers a tg+t conformation in the O-CH-CH-O bond sequence of the (R,R)-unit, and its unperturbed characteristic ratio depends considerably on stereoregularity: isotactic, 29, and syndiotactic, 0.83 (in chloroform at 25 °C). cis-PCHC comprising (R,S)- and/or (S,R)-units exclusively adopts either g-g+g+ or g-g-g+ conformation in the O-CH-CH-O bond sequence of the (R,S)-unit partly owing to intramolecular hydrogen bonds, and the dependence of the characteristic ratio of cis-PCHC on stereoregularity would be completely opposite to that of trans-PCHC: isotactic, 0.59, and syndiotactic, 25. In terms of the abovementioned characteristic parameters, properties of PCHCs synthesized so far with stereospecific catalysts are discussed.