Elastic modulus and relaxation times in telechelic associating polymers

Abstract

Dynamic mechanical measurements have been performed on solutions of HEUR-associating polymers with different molar mass, end-cap length, and extent of modification. These systems appear as Maxwellian fluids although at high frequencies a short-time relaxation process is evidenced for the systems with a strong hydrophobicity. This relaxation process could be attributed to the Rouse dynamics of active links in the temporary network. The high-frequency elastic modulus G_∞ decreases with increasing temperature according to an Arrhenius law. The associated activation energy decreases with increasing concentration. This is interpreted in terms of two contributions to the elastic modulus (osmostic and entropic elasticity).