title: Role of kosmotrope-chaotrope interactions at micelle surfaces on the stabilization of lyotropic nematic phases.
abstract: Three lyotropic quaternary systems of ionic surfactants were prepared to investigate the role of kosmotrope-chaotrope interactions at the micelle surfaces on stabilizing the different nematic phases. The ionic surfactants were potassium laurate (KL), sodium dodecylsulfate (SDS) and tetradecyltrimethylammonium bromide (TDTMABr), where KL is a kosmotrope surfactant, and others are chaotrope. The first system consisted of KL/decanol (DeOH)/water/alkali sulfate and the second of SDS/DeOH/water/alkali sulfate. The third system was prepared by adding sodium salts of chaotropic or kosmotropic anions to the primary mixture of TDTMABr/DeOH/water, separately. The characteristic textures of discotic nematic (ND), biaxial nematic (NB) and calamitic nematic (NC) phases were identified under polarizing light microscope. Laser conoscopy was employed to determine the uniaxial-to-biaxial phase transitions. The kosmotrope-kosmotrope or chaotrope-chaotrope interactions between the head groups of the surfactants and the ions of the electrolytes led to the stabilization of the NDphase. On the other hand, kosmotrope-chaotrope interactions stabilize the NBand/or NCphases.
authors.affiliation: Arts and Sciences Faculty, Department of Chemistry, Abant Izzet Baysal University, Golkoy, 14030, Bolu, Turkey. akpinar_e@ibu.edu.tr.
authors.forename: Erol
authors.initials: E
authors.lastname: Akpinar
authors.affiliation: Arts and Sciences Faculty, Department of Chemistry, Abant Izzet Baysal University, Golkoy, 14030, Bolu, Turkey.
authors.forename: Meric
authors.initials: M
authors.lastname: Turkmen
authors.affiliation: Arts and Sciences Faculty, Department of Chemistry, Abant Izzet Baysal University, Golkoy, 14030, Bolu, Turkey.
authors.forename: Cihan
authors.initials: C
authors.lastname: Canioz
authors.affiliation: Instituto de Física, Universidade de São Paulo, Rua do Matão, 1371, SP, 05508-090, São Paulo, Brazil.
authors.forename: Antônio
authors.initials: A
authors.lastname: Martins Figueiredo Neto
keywords: Soft Matter: Liquid crystals