title: Photoinduced increase in surfactant solution viscosity using azobenzene dicarboxylate for molecular switching.
abstract: We provide further insight into the photochemical control of viscoelasticity through the use of azobenzene sodium dicarboxylate for molecular switching. As a photoresponsive molecule, Sodium 3,3'-azobenzene dicarboxylate (3,3'-Azo2Na) was added to a solution of cetyltrimethylammonium bromide (CTAB)/sodium salicylate (NaSal), which is known for inducing the formation of wormlike micelles. This solution maintained a wormlike micellar structure, although a reduction in zero-shear viscosity was observed. When this mixed aqueous solution of CTAB/NaSal/3,3'-Azo2Na (16.7 mM each) was irradiated by ultraviolet light, the 3,3'-Azo2Na exhibited molecular trans-cis photoisomerization. We measured the dynamic viscoelasticity of the sample in the photostationary state and found that the zero-shear viscosity increased approximately sevenfold compared to the preirradiation state. This phenomenon is the opposite of the system wherein viscosity reduced by irradiation, as reported by us. We discuss the mechanism of this viscosity change.
authors.affiliation: Faculty of Science and Technology, Tokyo University of Science, Noda, Chiba, Japan.
authors.forename: Atsutoshi
authors.initials: A
authors.lastname: Matsumura
authors.forename: Kenichi
authors.initials: K
authors.lastname: Sakai
authors.forename: Hideki
authors.initials: H
authors.lastname: Sakai
authors.forename: Masahiko
authors.initials: M
authors.lastname: Abe
mesh_terms: D001391:Azo Compounds / Q000737:chemistry*; D000077286:Cetrimonium; D002593:Cetrimonium Compounds / Q000737:chemistry*; D008823:Micelles; D055668:Photochemical Processes; D012980:Sodium Salicylate / Q000737:chemistry*; D012996:Solutions; D013501:Surface-Active Agents / Q000737:chemistry*; D014783:Viscosity
chemical_list: D001391:Azo Compounds; D002593:Cetrimonium Compounds; D008823:Micelles; D012996:Solutions; D013501:Surface-Active Agents; D012980:Sodium Salicylate; D000077286:Cetrimonium