Generalized Statistical Mechanics and Scaling Behavior for Non-equilibrium Polymer Chains: II. Monomers Connected by Springs

概要

論文の詳細を見る
We use molecular dynamics simulations to study the relaxation process in a system of spatially well-mixed polymer chains and Lennard-Jones molecules, in which each polymer chain consists of monomers connected by springs of strength $k_{\text{spring}}$ and governed by bending and torsion angle potentials. The monomers are fluid-repelling, except for a small number of randomly chosen fluid-attractive “linker-sites”. The instantaneous temperatures of the monomers in polymer chains, $T^{*}_{\text{P}}$, and the fluid, $T^{*}_{\text{F}}$, are initially different, but they vary in time and their ratios $\Gamma^{*} = T^{*}_{\text{P}}/T^{*}_{\text{F}}$ approach a constant during the relaxation process. The velocity distributions of monomers in the relaxation process follow $q$-statistics with $q \geq 1$. We find that the value of $q$ and the limiting ratio of $\Gamma^{*}$ depend on $k_{\text{spring}}$; in the strong strength limit, they approach those for the system, in which each polymer chain consists of monomers connected by rigid bonds; in the weak strength limit, $\Gamma^{*}$ and $q$ approach 1 corresponding to Maxwell–Boltzmann distribution. The thermal contact between polymer chains and the fluid in our simulated systems provides a good basis for further study on the concept of temperature and the effective number of degrees of freedom in heterogeneous soft-matter systems.
2010-02-15