title: Clouding phenomenon and SANS studies on tetra-n-butylammonium dodecylsulfate micellar solutions in the absence and presence of salts.
abstract: Clouding phenomenon in aqueous micellar solutions of an anionic surfactant tetra-n-butylammonium dodecylsulfate (TBADS) has been observed as a function of surfactant concentration. Small-angle neutron scattering (SANS) experiments in these systems show clustering of micelles as the temperature approaches the cloud point (CP). The individual micelles and the clusters of micelles coexist at CP. The clustering of micelles depends on the surfactant concentration and temperature. It is proposed that clustering is due to depletion of H-bonded water present around the butyl chains at the micellar surface. This is associated with entropy gain which is considered to be the major thermodynamic factor related to micellar aggregation. The structures (clusters) that emerge depend on the relative lengths of the alkyl chains of the counterion and can be tuned by the temperature.
authors.affiliation: Department of Chemistry, Aligarh Muslim University, Aligarh 202 002, India. kabir7@rediffmail.com
authors.lastname: Kabir-ud-Din
authors.forename: Deepti
authors.initials: D
authors.lastname: Sharma
authors.forename: Ziya Ahmad
authors.initials: ZA
authors.lastname: Khan
authors.forename: V K
authors.initials: VK
authors.lastname: Aswal
authors.forename: Sanjeev
authors.initials: S
authors.lastname: Kumar
mesh_terms: D008823:Micelles; D033363:Neutron Diffraction; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D012492:Salts / Q000737:chemistry; D053838:Scattering, Small Angle; D012996:Solutions / Q000737:chemistry; D013499:Surface Properties; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D008823:Micelles; D000644:Quaternary Ammonium Compounds; D012492:Salts; D012996:Solutions; D014867:Water; C009405:tetrabutylammonium