VISCOMETRIC AND SPECTROSCOPIC STUDIES ON THE SOLUTION BEHAVIOR OF HYDROPHOBICALLY MODIFIED CELLULOSIC POLYMERS

The solution properties of hydroxyethyl cellulose (HEC) and hydrophobically modified hydroxyethyl cellulose (HM-HEC) have been investigated by means of viscometric and spectroscopic techniques involving free radical and fluorescent probes. The greater viscosity of HM-HEC solutions above a critical polymer concentration (Cp) of approximately 0·2% has been interpreted in terms of the formation of a three-dimensional network structure in which the polymer chains are effectively crosslinked by the intermolecular association of neighbouring hydrophobic side chains. Cp is considerably less than the predicted polymer coil overlap concentration (C*) of approximately 1%. The interaction of the polymers with an anionic surfactant, sodium dodecyl sulphate (SDS) has also been investigated. A mechanism involving the interaction of free surfactant with the regions of intermolecular hydrophobic association is suggested to account for the considerable differences in the rheological behaviour of the polymers in the presence of SDS. © 1990.