Triton X-100 micelles modulated by solubilized cinnamic acid analogues: The pH dependant micellar growth

Aqueous micellar solutions of a nonionic surfactant p-tert-octylphenoxy polyethylene (9.5) ether, Triton X-100 (TX-100) in the presence of cinnamic acid and its hydroxyl derivatives viz. p-coumaric acid, caffeic acid, ferulic acid and sinapic acid were examined by cloud point (CP), viscosity, dynamic light scattering (DLS), nuclear magnetic resonance (NMR) and small-angle neutron scattering (SANS) measurements. These solubilizates influence the CP, viscosity and micelle size of TX-100 depending on their hydrophobicity. Cinnamic acid, a biomedically useful compound displayed maximum growth in the micelles and was therefore studied in detail. We found that an increase in the cinnamic acid concentration, a decrease in pH and the presence of sodium chloride all favour the micellar growth at low temperature. The location of cinnamic acid in micelles was elucidated from H-1 NMR. SANS study showed that ellipsoidal micelles transform into rod-like on solubilization of cinnamic acid which otherwise change to spherical ones in alkaline medium. (C) 2014 Elsevier B.V. All rights reserved.