The viscosity B and D coefficient (Jones–Dole equation) studies in aqueous solutions of alkyltrimethylammonium bromides at 298.15 K

Abstract

The relative viscosity coefficient data of good precision and accuracy have been obtained for binary aqueous solutions of a homologous series of salts of alkyltrimethylammonium bromides (ranging from C6 to C16 carbon atoms in the side chain) at 298.15K. The concentration range has been extended to 0.0008mol·kg−1 for aqueous solutions of higher number of homogeneous series. The data pertain to both pre-micellar and post-micellar regions of the micelle forming salts. The application of the Jones–Dole equation in the form ((ηr−1)−Ac1/2)/c yielded the viscosity B and D coefficients. The same data are subjected to scrutiny by applying Vand viscosity equation. It has been found that the results of viscosity B coefficients obtained by both approaches show good agreement. The main result of this work is that application of the Vand equation enabled us to determine critical micelle concentration (cmc) in agreement with the similar data obtained by other methods. The variation of D coefficients for the series of compound shows that the solute–solute association effects due to hydrophobic interaction uniquely differentiate water structure making, structure breaking, aggregation and hydrophobic interaction effects. The applicability of the Vand equation is discussed on the basis of shape and size of the micelles, hydrodynamical effect and structural effects. Very high magnitudes of viscosity B coefficients have been obtained for higher members and these are attributed to high aggregation number and high volume fraction of micelle causing obstruction to the hydrodynamic flow properties of the solutions. Further the magnitudes of D coefficient in pre-micellar region are attributed to cation–cation and cation–anion–cation (pair and triplet interaction) attraction due to hydrophobic interactions in water.