Self-assembly and micellar transition in CTAB solutions triggered by 1-Octanol

Abstract

This study exploits higher-order micellar transition ranging from ellipsoidal to rodlike to wormlike induced by 1-octanol (C8OH) in an aqueous solution of cetyltrimethylammonium bromide (CTAB), characterizing phase behavior, rheology, and small-angle neutron scattering (SANS). The phase diagram for the ternary system CTAB-C8OH-water was constructed, which depicted the varied solution behavior. Such performance was further inferred from the rheology study (oscillatory-shear frequency sweep (ω) and viscosity (η)) that displayed an interesting solution behavior of CTAB solutions as a function of C8OH. It was observed that at low C8OH concentrations, the solutions appeared viscous/viscoelastic fluids that changed to an elastic gel with an infinite relaxation time at higher concentrations of C8OH, thereby confirming the existence of distinct micelle morphologies. Small-angle neutron scattering (SANS) provided various micellar parameters such as aggregation numbers (Nagg) and micellar size/shape. The experimental results were further validated with a computational simulation approach. The molecular dynamic (MD) study offered an insight into the molecular interactions and aggregation behavior through different analyses, including radial distribution function (RDF), radius of gyration (Rg), and solvent-accessible surface area (SASA).