Orientational anisotropy of bead-spring star chains during creep process



The bead-spring model for star chains (Rouse–Ham model) is a fundamental model for the polymer dynamics. Despite the importance of this model, its dynamics under the stress-controlled condition was not analyzed so far. For completeness of the model, the equation of motion of the Rouse–Ham chain was solved to derive an analytical expression of the orientation function S(n,t) for the stress-controlled creep process. This expression indicated that the segments near the free end of the star arm exhibit overshoot of their orientational anisotropy to compensate for the slow growth of the anisotropy near the branching point and that the distribution of the anisotropy along the arm contour becomes more heterogeneous with increasing arm number f. This correlation/interplay of the segments at different locations along the arm, not seen under the strain-controlled condition, is a natural consequence of the constant-stress requirement during the creep process. The corresponding interplay was noted also for respective Rouse–Ham eigenmodes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3501–3517, 2006