A molecular dynamic computation-experiment was performed on a system of 108 particles composed of a single polymer chain connected Np particles and solvent nature. The state considered was in the immediate neighborhood of the triple point of the system. The polymer itself is an analog to a freely jointed chain. The Lennard-Jones potential was used to represent the interactions between all particles including the interactions between non-nearest particles in the polymer except for the particles forming bonds, for which the interaction was expressed by a harmonic potential law.
The self-diffusion coefficients and time-dependent velocity autocorrelation functions of the center of mass of a polymer were calculated at various chain lengths Np, and interaction strengths between solvent molecules and polymer atoms.
For self-diffusion coefficients D, the Einstein relation holds goods; as chain length Np increases, the D value decreases at constant $\epsilon_{cs}$, the interaction strength between solvent and polymer atom; and D also decreases as $\epsilon_{cs}$ increases at constant chain length.
The velocity autocorrelation function decays roughly exponentially during the relaxation time; as chain length increases, the normalized of this function does not change during the relaxation time within statistical errors; and the relaxation time decreases if $\epsilon_{cs}$ increases, whereas the polymer molecule suffers larger backscattering as $\epsilon_{cs}$ increases.
The diffusion coefficients in various conditions reveal that our systems are in a free-draining limit.
용액중의 한개의 고분자 molecular dynamic simulation 결과, chain length 및 solvent 와 polymer 간의 interaction strength 의 변화에 따른 diffusion coefficient 및 velocity autocorrelation function 의 거동을 분자의 transport 이론 및 Kirkwood-Riesman 의 유체역학적인 이론의 두가지 관점에서 살펴 본 결과 본 연구의 결과가 이들 이론의 예견한 바와 잘 일치하며, 더욱이 Kirkwood-Riesman Theory 와의 비교로 부터, 많은 사람들이 Monte Carlo 방법으로 computer 실험할때 결여되는 것으로 예상하는 고분자의 segment 간의 유체역학적인 interaction이 거의 없는 것으로 나타났으며, 이는 그들의 이론과도 잘 일치한다.
