title: Interaction between a nonionic surfactant and a hydrophobically modified 2-hydroxyethyl cellulose.
abstract: Interaction between the nonionic surfactant Tergitol 15-S-7 and hydrophobically modified 2-hydroxyethyl cellulose (HMHEC) was studied rheologically in a semidilute regime of HMHEC. The low-shear viscosity of HMHEC was increased with addition of surfactant from 25 to 250 ppm, in which the critical micelle concentration of surfactant was near 39 ppm, and then decreased to a value smaller than that of pure HMHEC with further addition of surfactant to 1000 ppm. An interesting shear-induced phenomenon was observed. The steady-state shear measurements show that there exist crossovers between viscosity-shear rate curves of HMHEC solutions with and without surfactant added, whereas it was not observed in the HEC-surfactant systems. Moreover, added Tergitol 15-S-7 reversed the temperature effect on the viscosity of the HMHEC solution. That is, increasing temperature to or near the cloud point raises the viscosity of the HMHEC-surfactant aggregates, in contrast to the viscosity decrease in the pure HMHEC solutions. A possible mechanism based on the necklace model and the clouding phenomenon is conjecturally introduced to explain such phenomena.
authors.affiliation: Department of Chemical and Biomolecular Engineering, The National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260.
authors.forename: Dongshun
authors.initials: D
authors.lastname: Bai
authors.forename: Cho Cho
authors.initials: CC
authors.lastname: Khin
authors.forename: Shing Bor
authors.initials: SB
authors.lastname: Chen
authors.forename: Chih-Chang
authors.initials: CC
authors.lastname: Tsai
authors.forename: Bing-Hung
authors.initials: BH
authors.lastname: Chen
mesh_terms: D002482:Cellulose / Q000031:analogs & derivatives* / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D013501:Surface-Active Agents; D002482:Cellulose; C002283:hydroxyethylcellulose