Title
Viscosity of hydroxypropyl cellulose solutions in non-entangled and entangled states
Authors
MARIA BERCEA and PATRICK NAVARD

Received Dedicated to Acad. Bogdan C. Simionescu on the occasion of his 70^th anniversary
Published Volume 52 Issue 7-8 July-August
Keywords hydroxypropyl cellulose, viscosity, non-entangled coils, entangled state

Abstract
The viscosity of isotropic hydroxypropyl cellulose (HPC) solutions was investigated in pure water and aqueous solution of 10% glucose as solvent. The intrinsic viscosity, [η], was determined by using an approach developed by Wolf, which is able to describe the viscosity evolution over a large domain of concentrations (c) for any type of macromolecular structure. The transition between dilute solution (i.e. the state with isolated non-interacting coils) and semidilute solution (i.e. the state where coils are touching each other, but with not so many interactions between chains) was evidenced for the HPC solutions. Newtonian viscosity resulted from the flow curves determined in semidilute concentration regime. From the plot of the specific viscosity as a function of a dimensionless parameter, c×[η] (defined as reduced concentration), the entangled and non-entangled states were delimitated for the HPC aqueous solutions. A critical overlap parameter of 2.4 was determined. In aqueous solution of 10% glucose, the semidilute non-entangled state was depicted for high molecular HPC in the investigated range of concentrations (below 4 g/dL).