화학공학소재연구정보센터
Langmuir, Vol.19, No.24, 10036-10043, 2003
Gels of hydrophobically modified hydroxyethyl cellulose cross-linked by amylose: Competition by added surfactants
Previous work has shown that amylose (AM) can cross-link hydrophobically modified polymers by inclusion complexation, whereby thermoreversible cold-setting gels are formed. This work investigates, mainly by rheology, the competition effect of seven different anionic, cationic, and nonionic surfactants when mixed at room temperature into preformed gels of AM and hydrophobically modified hydroxyethyl cellulose (HMHEC). The aqueous mixtures of AM, HMHEC, and surfactant are compared with reference mixtures of AM-HMHEC, AM-surfactant, and HMHEC-surfactant, respectively. All the added surfactants interact with HMHEC, giving rise to the well-known increase in shear storage modulus compared to pure HMHEC solution. In addition, all added surfactants, except Triton X-100, form inclusion complexes with AM. The mechanical spectra of the AM/HMHEC/surfactant mixtures are closely similar to those containing only HMHEC and surfactant but quite distinct from that of the AM-HMHEC gel, demonstrating that all surfactants can compete with the AM-HMHEC complexation. Heat treatment of the mixtures produced no significant changes. A detailed analysis of the competition by two surfactants, sodium dodecyl sulfate (SDS) and sodium octyl sulfate (SOS), showed that much larger amounts of added SOS were required for an efficient competition. The rheological characteristics indicate that the HMHEC hydrophobes are simultaneously engaged in both mixed micelles with the added surfactant and inclusion complexes with AM over a large concentration range of added surfactant.