Volumetric, viscometric and 1H NMR spectroscopic studies in (polyhydroxy solute + CTAB + H2O) ternary solutions

Abstract

To investigate the molecular interactions of polyhydroxy solutes with cetyltrimethylammonium bromide (CTAB) surfactant, we have measured the densities and viscosities of (+)-d-xylose, xylitol, (−)-l-sorbose, d-sorbitol, (+)-d-glucose, and (+)-d-maltose in (4.0, 8.0, and 12.0)·10−4mol·kg−1 CTAB(aq) solutions at (298.15, 308.15 and 318.15) K. The density data have been utilized to evaluate apparent molar volumes (V2,ϕ), partial molar volumes (V2°) and their transfer (ΔtV2°) values at infinite-dilution. The viscosity data were analyzed using the Jones-Dole equation and further used to calculate the viscosity B-coefficients and transfer B-coefficients, ΔtB. The structure-making/-breaking behavior of the polyhydroxy solutes were analyzed using the signs and magnitude of (∂2V2°/∂T2)P and dB/dT coefficients. It has been observed that the positive ΔtV2° and ΔtB values increase with increasing CTAB concentration. 1H NMR spectroscopic study of polyhydroxy solutes was also carried out in mB=(4.0, 8.0, and 12.0)·10−4mol·kg−1 CTAB solutions which were made in 9:1 (w/w) H2O+D2O solvent. NMR results showed higher downfield shift in ternary (polyhydroxy solute+CTAB+9:1 (w/w) H2O+D2O) solutions as compared to pure CTAB solution, hence suggested the predominance of hydrophilic-ionic interactions over hydrophobic-ionic interactions.