Viscoelasticity of a Stretched Semiflexible Polymer Chain with Fixed Ends

Abstract

Regularities of the decay of time correlation functions of fluctuations of the microscopic stress tensor characterizing viscoelastic properties for statically stretched chains composed of elastic units with bending stiffness are studied by molecular dynamics and analytically. Chains with the persistent length smaller than the contour length at degrees of extension up to break are considered. In the region of high extensions, where distortions of the local structure of a chain appear, the decay of correlation functions can be described by the modified Rouse model consisting of subchains with anisotropic rigidities depending on the equilibrium chain extension. This makes it possible to determine the relaxation times and moduli of strongly stretched chains, which is necessary in studying the strength of polymer networks. For correlation functions, the analytical relation is formulated that takes into account the contribution of transverse bending fluctuations and agrees with the results of computer simulation at low extensions. A change in the correlation functions with the extension of long semiflexible chains is qualitatively similar to that for flexible chains, but quantitatively is appreciably different.