Associative and Entanglement Contributions to the Solution Rheology of a Bacterial Polysaccharide

Abstract

We report the viscosity of semidilute solutions of a bacterially synthesized polysaccharide—a partially deacetylated poly-N-acetylglucosamine—as measured by microrheology. This polymer, commonly called polysaccharide intercellular adhesin (PIA), is synthesized by Staphylococcal strains; it is a principal component of the biofilms of these bacteria. We show that the concentration-dependent viscosity of PIA at a pH in which it is associated can be predicted using the Heo–Larson equation for entangled polymers [J. Rheol. 2005, 49 (5), 1117−1128], if the molecular parameters of the equation are measured in its associated state. This agreement is consistent with PIA adopting a concentration-dependent scaling of the viscosity that is dominated by entanglements and intermolecular associations, as described in the theory of Rubinstein and Semenov [Macromolecules 2001, 34 (4), 1058−1068]. The zero-shear specific viscosity, ηsp, measured in the concentration range, cPIA = 0.1–13 wt %, scales as ηsp ∼ cPIA1.27±0.15 ...