Linear and nonlinear rheological characterization of temporary networks of telechelic polybutadiene

Apolar polymers with hydrogen-bonding or ionic end-groups have a natural tendency to form temporary networks and are as such interesting systems to study the interplay between topological interactions, i.e. entanglements, and reversible supramolecular linkages. While some rheological and structural characterization of such systems has been published in the past, no systematic study on the respective influences of topological vs. supramolecular interactions has been reported. In this work, we focus on the linear and non linear rheological characterization of telechelic polybutadienes (PBd) with carboxylic end groups neutralized with various inorganic and organic bases. A difunctional carboxylic acid terminated PBd shows only very weak associative behavior with a slightly increased temperature dependence by comparison with the neat polymer. The neutralization of the acid end-groups, however, leads to the formation of a reversible network, whose bonding strength and characteristic relaxation time depend very much on the nature of the ion, and to a much higher temperature dependence. An increase of the relaxation time by several orders of magnitude is observed together with a dramatic change of the plateau modulus by comparison with the reference polymer.