The role of molecular mechanics in the prediction of the chain conformation of polymers in the crystalline state: Syndiotactic polymers

Molecular mechanics methods have been used in order to find the conformatio ns of various syndiotactic polymers in crystals. Three different classes of polymers have been examined: i) polyolefins, such as poly(propylene), poly styrene, poly(l-butene) and poly(1,2-butadiene); ii) polydienes, such as ci s-1,4-poly(1,3-pentadiene); iii) alternating copolymers of carbon monoxide with styrene or styrene derivatives. The presence of conformational polymor phism in some of the studied polymers is predicted and explained by maps an d minimizations of the conformational energy. The calculated internal param eters and chain axis repeats of all the considered polymers result in very good agreement with X-ray experimental data reported in literature. The rol e of intramolecular nonbonded interactions in determining the conformations of the polymer chains is thoroughly discussed.