Molecular dynamics analysis of transitions between rotational isomers in polymethylene
- 1 October 1991
- journal article
- research article
- Published by AIP Publishing in The Journal of Chemical Physics
- Vol. 95 (7), 5348-5354
- https://doi.org/10.1063/1.461649
Abstract
Molecular dynamics trajectories have been computed and analyzed for linear chains, with sizes ranging from C10H22 to C100H202, and for cyclic C100H200. All hydrogen atoms are included discretely. All bond lengths, bond angles, and torsion angles are variable. Hazard plots show a tendency, at very short times, for correlations between rotational isomeric transitions at bond i and i±2, in much the same manner as in the Brownian dynamics simulations reported by Helfand and co-workers. This correlation of next nearest neighbor bonds in isolated polyethylene chains is much weaker than the correlation found for next nearest neighbor CH–CH2 bonds in poly(1,4-trans-butadiene) confined to the channel formed by crystalline perhydrotriphenylene [Dodge and Mattice, Macromolecules 24, 2709 (1991)]. Less than half of the rotational isomeric transitions observed in the entire trajectory for C50H102 can be described as strongly coupled next nearest neighbor transitions. If correlated motions are identified with successive transitions, which occur within a time interval of Δt≤1 ps, only 18% of the transitions occur through cooperative motion of bonds i and i±2. An analysis of the entire data set of 2482 rotational isomeric state transitions, observed in a 3.7 ns trajectory for C50H102 at 400 K, was performed using a formalism that treats the transitions at different bonds as being independent. On time scales of 0.1 ns or longer, the analysis based on independent bonds accounts reasonably well for the results from the molecular dynamics simulations. At shorter times the molecular dynamics simulation reveals a higher mobility than implied by the analysis assuming independent bonds, presumably due to the influence of correlations that are important at shorter times.Keywords
This publication has 21 references indexed in Scilit:
- Conformational statistics of poly(dimethylsiloxane). 1. Probability distribution of rotational isomers from molecular dynamics simulationsMacromolecules, 1991
- Simulation by molecular dynamics of poly(1,4-trans-butadiene) as an inclusion complex in the channel of crystalline perhydrotriphenyleneMacromolecules, 1991
- Rheology of n-alkanes by nonequilibrium molecular dynamicsThe Journal of Chemical Physics, 1987
- CHARMM: A program for macromolecular energy, minimization, and dynamics calculationsJournal of Computational Chemistry, 1983
- Stochastic molecular dynamics study of t r a n s–g a u c h e isomerization processes in simple chain moleculesThe Journal of Chemical Physics, 1980
- Brownian Dynamics Study of Polymer Conformational Transitions±Macromolecules, 1980
- Brownian dynamics study of polymer conformational transitionsThe Journal of Chemical Physics, 1979
- Simulation of n-butane using a skeletal alkane modelThe Journal of Chemical Physics, 1978
- Simulation of polymer dynamics. I. General theoryThe Journal of Chemical Physics, 1978
- Dynamics of stiff polymer chains. IThe Journal of Chemical Physics, 1974