title: Wormlike micelles formed by mixed cationic and anionic gemini surfactants in aqueous solution.
abstract: The formation and the properties of wormlike micelles in aqueous solutions of mixed cationic and anionic gemini surfactants, 2-hydroxyl-propanediyl-α,ω-bis(dimethyldodecylammonium bromide) (12-3(OH)-12) and O,O'-bis(sodium 2-dodecylcarboxylate)-p-benzenediol (C(12)ϕC(12)), have been studied by steady-state and dynamic rheological measurements at 25°C. With the addition of a small amount of C(12)ϕC(12) into the solution of 12-3(OH)-12, the total surfactant concentration of which was always kept at 80 mmol L(-1), the solution viscosity was strongly enhanced and its maximum was much larger than that of the mixed system of propanediyl-α,ω-bis(dimethyldodecylammonium bromide) (12-3-12) and C(12)ϕC(12). The results of dynamic rheology measurements showed that 12-3(OH)-12/C(12)ϕC(12) formed longer wormlike micelles in comparison with 12-3-12/C(12)ϕC(12). This was attributed to the effect of hydrogen bonding occurring between 12-3(OH)-12 molecules, which was an effective driving force promoting micellar growth. As few C(12)ϕC(12) participated in the micelles, the electrostatic attraction between the oppositely charged head groups of 12-3(OH)-12 and C(12)ϕC(12) made the molecules in the aggregates pack more tightly. This reinforced the hydrogen-bonding interactions and greatly promoted the micellar growth.
authors.affiliation: Institute of Colloid and Interface Chemistry, College of Chemistry and Chemical Engineering, Fuzhou University, Fuzhou, Fujian, People's Republic of China.
authors.forename: Xiaomei
authors.initials: X
authors.lastname: Pei
authors.forename: Jianxi
authors.initials: J
authors.lastname: Zhao
authors.forename: Xilian
authors.initials: X
authors.lastname: Wei