CONFORMATIONS OF FOLD PART IN ISOTACTIC POLYPROPYLENE LAMELLA WITH DIAMOND LATTICE MODEL

Based on the perfect rotational isomeric state model of isotactic poly propylene, the separation distances between an initial left helix stem and its re-entry stems have been investigated. The intervals are defi ned by the formulae D-1 = 1.54/3 root 8(k(1)(2) + k(2)(2) + k(1)k(2))/ 3 (x 10(-1) nm) for the left helix re-entry stem and D-2 = 1.54/3 root 8[k(1)(2) + k(2)(2) + (k(1) - 1)k(2) + 1/3]/3 (x 10(-1) nm) for the r ight helix re-entry stem, where k(1) and k(2) are integers. The right helix one is less existing because of possessing high energy. The most plausible fold conformation is tg(-)tg(-)tg(+)g(+)g(-) for the most a djacent (010) fold. The next minimum energy fold segments are tg(-)g(- )tg(+)tg(+)tg(-), g(+)g(-)tg(-)tg(+)g(+)t and g(+)g(-)g(-)tg(+)tg(+)t.