1999 REU Participants

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Laura MacManus

Laura is a junior at the College of St. Benedict majoring in Chemistry, minoring in Environmental Studies.

Brownian Motion of Semi-flexible Polymer Chains
Laura MacManus
College of St. Benedict

David Morse
Department of Chemical Engineering and Materials Science, University of Minnesota

The Brownian motion of semi-flexibly polymers in dilute solution was explored through computer simulation. The computer program, Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS), was used to simulate the behavior of semi-flexible polymer chains in solutions and observe the systemÕs response to an initial step shear. The relaxation of the polymer chains from their initially deformed conformations was analyzed in terms of the stress in the system. The total stress in the system was decomposed into three components: stress due to the orientation of the molecules, stress due to the curvature of the molecules, and stress due to the tension in the bonds of the molecules. Calculations of the cross-correlations of these three components of the stress indicate a possible correlation between the orientation stress and the curvature stress, suggesting that modifications are necessary in the calculation of the curvature stress. The effects of altering system parameters were also explored. Reproducible results were obtained for the calculation of the tension stress while increasing or decreasing the damping constant, which correspondingly increased or decreased the diffusivity of the polymers in solution.