SIMULATION BY MOLECULAR-DYNAMICS OF POLY(1,4-TRANS-BUTADIENE) AS AN INCLUSION COMPLEX IN THE CHANNEL OF CRYSTALLINE PERHYDROTRIPHENYLENE

A molecular dynamics simulation has been performed for a poly(1,4-trans-butadiene) chain, with a degree of polymerization of 10, confined to a channel produced by crystallization of 90 molecules of perhydrotriphenylene. All hydrogen atoms are treated explicitly in the simulation. The entire system contains 4422 atoms. No rotational isomerization is observed in the polymer if the perhydrotriphenylene matrix is artificially constrained to be rigid, with the geometry observed for the crystal. When this artificial constraint is removed, coupled rotational isomerizations at bonds i and i + 2 are observed in the polymer. These rotational isomerizations produce very little displacement of the tails, and in this respect they are similar to the transitions observed by Helfand and co-workers in the simulation by Brownian dynamics of a simple chain in a viscous environment. They can randomize the orientation of the C-H bond vectors within the time scale reported by Sozzani et al3. The coupled transitions can be written as A+TA- --> A-TA+, where A +/- and T denote anticlinal +/- and trans, respectively. The anticlinal states occur at CH-CH2 bonds separated by a CH = CH bond or a CH2-CH2 bond in a trans state.