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Keywords:

  • molecular length;
  • recurrence equations;
  • rubber;
  • strain;
  • stretch functions

Abstract

Thumbnail image of graphical abstract

The tube theory represents a powerful tool for the description of polymer behaviour. In this theory, the term in the form of an integral over a full solid angle of a magnitude of deformed unit vector represents the stretch function. This term relates the lengths of the random walk of a molecule in deformed and undeformed states. For the case of the Doi-Edwards model, the integrand is raised to a power of one, however, for other models the power differs from one. The aim of this contribution is to derive an analytical algebraic approximation of a general form of this integral with the integrand raised to an arbitrary power within the physically justified interval between zero and two.