The adsorption of hydroxyethyl cellulose and hydrophobically modified hydroxyethyl cellulose onto polystyrene latex

Abstract

The adsorption of hydroxyethyl cellulose (HEC) and hydrophobically modified hydroxyethyl cellulose (HMHEC) onto anionic polystyrene latex particles has been studied. The amount of polymer adsorbed much greater for HMHEC than for HEC, and studies using electron spin resonance spectroscopy (ESR) indicated that HMHEC adopted a much more extended adsorbed layer configuration with a greater proportion of segments protruding into solution in the form of loops and tails. The adsorption capacities of both polymers were not affected by the presence of electrolyte, although they were greatly reduced by the addition of both non-ionic and anionic surfactant. HEC was completely prevented from adsorbing at a sodium dodecyl sulphate (SDS) concentration of 2 · 10 −2 mol dm −3 and above and at an alkyl polyoxyethylene ether-type surfactant (C 11EO 8) concentration of 5 · 10 −4 mol dm −1 and above. In contrast, HMHEC was still able to adsorb under these conditions, albeit to a much lower level than observed in the absence of surfactant. The stability of the latex dispersions in the presence of various concentrations of polymer was monitored by turbidity measurements. Both HEC and HMHEC induced bridging flocculation at low surface coverages when salt was present to compress the electrical double layer of the latex particles and both conferred steric stability at high surface coverages.