POLYMER SURFACTANT INTERACTIONS AND THE ASSOCIATION BEHAVIOR OF HYDROPHOBICALLY MODIFIED HYDROXYETHYLCELLULOSE

The association behavior of hydrophobically modified hydroxyethylcellulose (HMHEC) and its interactions with two different types of surfactants, sodium dodecyl sulphate (SDS) and dodecyloxyheptaethoxyethyl alcohol (C12EO8) in dilute solutions have been studied using fluorescence spectroscopy, surface tension and viscometric techniques. Unmodified hydroxyethylcellulose (HEC) of the same molecular weight and degree of substitution as the HMHEC has also been examined for the purpose of comparison. Fluorescence data show that the hydrophobic groups of the HMHEC associate to form clusters above a critical polymer concentration of 500 ppm. Also, the presence of hydrophobic groups on the polymer enhances the interactions between the polymer and nonionic surfactants. Surface tension results support this observation. The viscosity results suggest that the interactions between the surfactant and the polymer affect both interpolymer-polymer association as well as chain expansion. Chain expansion due to changes in the polymer structure of the HMHEC is similar to that observed in a mixed solvent system. The increased polymer-polymer association in the case of HMHEC-SDS was found to cause phase separation. Such association was effectively prevented above the critical micellar concentration (c.m.c.) of SDS by the polymer bound micelles. © 1990.