Primitive Chain Network Simulations of Conformational Relaxation for Individual Molecules in the Entangled State. II. Retraction from Stretched States.

Abstract

Although some experiments have addressed individual chain dynamics in the entangled state, the behavior of the quantity measured in the experiments, and its relation to chain conformation, deserves further study. In our previous work using primitive chain network simulations at equilibrium (Masubuchi et al, Nihon Reoroji Gakkaisi (J. Soc. Rheol. Jpn.) 36, 181, 2008), we examined the relaxation of the chain extension, x, which is the maximum distance between segments of any given chain. In this supplementary study we performed simulations under step shear deformations, away from the equilibrium state. It was found that the x relaxation under deformation is qualitatively similar to that of the relaxation modulus, where slow relaxation modes are insensitive to deformation while the intensity of fast modes is enhanced. As a result the longest relaxation time of x was found to be the same as the equilibrium state, and different from that of stress. For what concerns the behavior of the fast modes, less damping was observed for the relaxation of x than that for stress.