Creep dynamics of non-entangled miscible polymer blends and block copolymers

The bead-spring model, as a fundamental model of polymer physics, has been widely utilized so far for polymer chains under the strain-controlled conditions. Nevertheless, full analysis of conformational dynamics of the polymer chains during the creep (stress-controlled) process has not been given until recently by Watanabe and Inoue (Rheol. Acta 43: 634-644, 2004a). In this paper, this analysis is extended to disordered block copolymers and miscible polymer blends for which an effect of frictional distribution/heterogeneity manifests. Due to the requirement of constant stress, segments of different blocks of the block copolymers as well as those of different components of the polymer blends exhibit correlated anisotropic change during the creep process. Furthermore, this change contains two stages with a growth of the orientational correlation among the segments, that is, the first segmental stage where the anisotropic change reflects the intrinsic mobility of segments, and the second global stage where the anisotropy approaches the steady-state defined with respect to the specific position of a chain.