Rheological properties of sulfoacetate derivatives of cellulose.

Water-soluble cellulose acetate sulfate derivatives (CAS) have been prepared through chemical reaction involving sulfuric acid as a catalyst. These CAS have been obtained from cellulosic materials of different origins (pure cellulose, wheat bran, maize bran) and their rheological behavior in salt-free aqueous solution has been estimated in dilute and semi-dilute regime using dynamic viscoelastic and viscosity measurements. Influence of concentration, temperature of solubilization and temperature of measurement has been investigated. Weak gel-like properties were exhibited at elevated concentration (typically above 7-8 g/L). These systems also exhibited thixotropic properties: the structure was partly broken down upon shearing and recovered at rest. They also displayed thermoreversibility with large hysteresis, the melting temperature being approximately 15 degrees C higher than the temperature at which gelation took place. These overall observations clearly indicate that these distinctive properties arise from intermolecular association of the macromolecular chains of the cellulose derivative.