title: Bilayers and wormlike micelles at high pH in fatty acid soap systems.
abstract: Bilayers at high pH in the fatty acid systems of palmitic acid/KOH/H2O, palmitic acid/CsOH/H2O, stearic acid/KOH/H2O and stearic acid/CsOH/H2O can form spontaneously (Xu et al., 2014, 2015). In this work, the bilayers can still be observed at 25°C with an increase of the concentration of fatty acids. We found that wormlike micelles can also be prepared in the fatty acid soap systems at high pH, even though the temperature was increased to be 50°C. The viscoelasticity, apparent viscosity, yield stress of the bilayers were determined by the rheological measurements. Wormlike micelles were identified by cryogenic transmission electron microscopy (cryo-TEM) and emphasized by the rheological characterizations, which are in accordance with the Maxwell fluids with good fit of Cole-Cole plots. The phase transition temperature was determined by differential scanning calorimetry (DSC) and the transition process was recorded. The regulating role of counterions of fatty acids were discussed by (CH3)4N(+), (C2H5)4N(+), (C3H7)4N(+), and (C4H9)4N(+) as comparison, concluding that counterions with appropriate hydrated radius were the vital factor in the formation wormlike micelles.
authors.affiliation: Key Laboratory for Colloid and Interface Chemistry & Key Laboratory of Special Aggregated Materials, Shandong University, Ministry of Education, Jinan 250100, PR China.
authors.forename: Wenlong
authors.initials: W
authors.lastname: Xu
authors.affiliation: Key Laboratory for Colloid and Interface Chemistry & Key Laboratory of Special Aggregated Materials, Shandong University, Ministry of Education, Jinan 250100, PR China.
authors.forename: Huizhong
authors.initials: H
authors.lastname: Liu
authors.affiliation: Key Laboratory for Colloid and Interface Chemistry & Key Laboratory of Special Aggregated Materials, Shandong University, Ministry of Education, Jinan 250100, PR China.
authors.forename: Aixin
authors.initials: A
authors.lastname: Song
authors.affiliation: Key Laboratory for Colloid and Interface Chemistry & Key Laboratory of Special Aggregated Materials, Shandong University, Ministry of Education, Jinan 250100, PR China. Electronic address: jhao@sdu.edu.cn.
authors.forename: Jingcheng
authors.initials: J
authors.lastname: Hao
keywords: Counterions; Fatty acids; Regulating effect; Wormlike micelles; pH