Rheological properties of binary associating polymers

Dynamics of associating polymer solutions above the reversible gelation point are studied. Each macromolecule consists of a soluble backbone (B) and a small fraction of specific strongly interacting groups (A or C stickers) attached to B. A mixture of B-A and B-C associating polymers with 1: 1 stoichiometric ratio is considered. As a result of AC association, the polymers reversibly gelate above the overlap concentration. It is shown that (1) the network strands are linear complexes (double chains) of B-A and B-C; ( 2) diffusion of the network junction points is characterized by an apparent activation energy, which can be significantly higher than the energy of one AC bond; ( 3) most importantly, the randomness of sticker distribution along the chain can significantly slow down the network relaxation leading to a markedly non-Maxwellian viscoelastic behavior. The theory elucidates the most essential features of rheological behavior of polysaccharide associating systems (with A = adamantyl moiety, C = beta-cyclodextrin, B=either chitosan or hyaluronan) including similar behavior of G' and G '' in a wide frequency range, strong temperature dependence of the characteristic frequency omega(x), and an extremely strong effect of added free stickers (fC) on the dynamics.