(33g) Rheology and Pinching Dynamics of Associative Polysaccharide Solutions

Associative polysaccharides are cellulose derivative polymers with multiple short, side-chain (hydrophobic stickers) that associate in aqueous solution typically used as thickeners for an extensive range of aqueous-based formulations. Characterizing the influence of hydrophobically- associative stickers on the response to extensional flows that spontaneously arise in pinching necks formed during spraying, jetting or coating fluids have remained longstanding experimental and analytical challenges, due to relatively low viscosity and elasticity of industrially-relevant systems. In this study, we contrast the shear and extensional rheology as well as pinching dynamics of hydrophobically-modified hydroxyethyl cellulose (hmHEC) as sticky polymer with the bare chain (HEC) of a higher molecular weight using the recently developed dripping-onto- substrate (DoS) rheometry protocols. We show that the presence of stickers enhances zero shear viscosity as well as relaxation time (elasticity), and both properties display stronger concentration-dependent variation for sticky polymers. Striking differences are observed in neck shapes and neck radius evolution profiles, as well as the extensional viscosity as a function of both strain and strain rate. We present a comprehensive analysis of changes in pinching dynamics, concentration-dependent variation in steady, terminal viscosity as well as filament lifespan as a function of concentration for the sticky polymer, and describe the influence of multiple stickers on macromolecular strain, relaxation, and dynamics of associative polysaccharides. Finally, we discuss the influence of associative polysaccharides on the pinching dynamics and rheology of multicomponent formulations.