Dominant interactions in the conformation of isotactic polypropylene: 1. Intrachain energy

A calculation is presented of the intrachain component of the conformational energy of isotactic polypropylene. Multiple minima are found for the energy as a function of the three torsional angles, with a strong dependence noted on the rotation of the methyl group. A comparison is made between the energies of ordered and disordered chain conformations constructed to produce the experimentally observed 31 helix.