LAUSR

Abstract Micellar aggregates formed in aqueous solution of Gemini surfactant: N, N′-didodecyl-N,N, N′,N′ tetramethyl-N,N′-ethanediyldiammonium dibromide (12-2-12), in presence of organic additive: Phenyl Propiolic acid (PPA), has been systematically characterized by rheology, 1H-NMR, fluorescence spectroscopy, dynamic light scattering (DLS), small angle neutron scattering (SANS), transmission electron microscopy (TEM), and contact angle (CA) techniques as a function of temperature. 12-2-12 undergo micellar transition from elongated ellipsoidal micelles to unilamellar vesicles (ULV) upon addition of varying amount of PPA as a function of temperature which was inferred by scattering and microscopy results. The quantification of the geometrical parameters of 12-2-12 micelles was achieved by a complete fit of the obtained SANS data using prolate ellipsoidal form factor and the structure factor model thereby confirming the presence of elongated ellipsoidal micelles and ULV. Variation of the viscosity with the shear rate for the ratio 50 mM 12-2-12: 10 mM PPA exhibited the typical viscoelastic characteristics which are further investigated by dynamic rheological measurements. 1H-NMR study indicated the substantial change in the chemical shifts of the protons for 12-2-12 with the addition of PPA, thereby inferring the significant interaction between the two components leading to such micellar transition. Furthermore, DLS and Fluorescence study suggested the formation, aggregation and collapse procedure of the network structures of the 12-2-12+PPA system, which either resulted in increase or decrease of viscosity as a function of PPA concentration and temperature. Such observation is evidently complimented by TEM findings and CA study. The structural dynamics of these aggregates corresponding to the interaction between them are well correlated with quantum simulation approach using Density Functional Theory (DFT)/B3LYP with the basis set 3-21G method.