NOPR Collection:

Physicochemical studies on microemulsions IV-A comprehensive estimation of the energetics

2017-02-10T10:08:49Z

Title: Physicochemical studies on microemulsions IV-A comprehensive estimation of the energetics Authors: Paul, Subinoy; Moulik, S P Abstract: A comprehensive presentation of the proposed thermodynamic theories on microemulsion formation has been made. The thermodynamic functions (parameters) viz. van der Waals potential, configurational entropy, potential energy and droplet free energy in water-in-oil microemulsion stabilized by the amphiphiles aerosol OT, sodium dodecyl sulphate, cetyltrimethylammonium bromide, butanol and hex-ylamine have been evaluated. The estimated van der Waals potential has been found to be much lower than the critical phase separation value of 10.6. Inter droplet interaction leading to amphiphile penetration has been considered to be responsible for this effect. It has been observed that the effective surfactant chain length has significant effect on the droplet free energy and the potential energy. The hydrodynamic radius of the microwater droplets has been found to be inversely proportional to the configurational entropy. Page(s): 931-937

Clouding and aggregation behaviour of ethylene oxide/propylene oxide/ethylene oxide block copolymers in aqueous media in the presence of sodium dodecyl sulphate

2017-02-10T10:07:29Z

Title: Clouding and aggregation behaviour of ethylene oxide/propylene oxide/ethylene oxide block copolymers in aqueous media in the presence of sodium dodecyl sulphate Authors: Lad, K; Bahadur, A; Pandya, K; Bahadur, P Abstract: The interaction of ethylene oxide-propylene oxide-ethylene oxide block copolymers (F-68, L-64 and P-85) with sodium dodecyl sulphate (SDS) in aqueous medium has been studied using various physical properties viz., cloud point, surface tension, dye solubilization, conductivity and viscosity. Dynamic light scattering (DLS) has been used to determine the size of aggregates of copolymer/SDS micelles. The cloud points (CP) of copolymer solutions increase in the presence of SDS; the CP increase is dependent on the hydrophobicity of the copolymer and its concentration. Surface tension/dye solubilization data support the aggregation of SDS taking place at concentration much below its critical micelle concentration (cmc); the copolymer-SDS mixed systems have enhanced surface activity and solubilizing power. Viscosity data reveal that the copolymer-SDS complex (or mixed micelles) possesses polyelectrolyte-like nature. The strength of. the SDS-copolymer interaction seems in the order P-85 > L-64 > F-68. DLS data indicate that the addition of SDS to L-64 solution in water gradually decreases the hydrodynamic radius of the micelles; however, no change in micelle size of L-64 is detected in the presence of 1.0M NaCI on addition of SDS. Small quantities of copolymer added to SDS solutions in water in the presence of calcium chloride reduce the turbidity and thus improve the hardness tolerance. Page(s): 938-945

Bi-ionic potentials and electrochemical characterization of membranes

2017-02-10T10:05:23Z

Title: Bi-ionic potentials and electrochemical characterization of membranes Authors: Singh, Kehar; Tiwari, A K Abstract: Bi-ionic membrane potential studies have been carried out to explore possibilities of electrochemical characterization of cellulose acetate and Dowex-50 membranes. Theoretical framework developed for the estimation of ionic transport numbers and fixed charge density from bi-ionic potentials has been outlined and used to obtain these electrochemical parameters for KCl-NaCl, KCI-NH₄Cl and NaCI-NH₄Cl bi-ionic systems. The observed trend in the variation of fixed charge density with concentration is consistent with that derived earlier using membrane potential data. Page(s): 946-949

Viscosity studies of aqueous mixed electrolyte solutions

2017-02-10T10:03:59Z

Title: Viscosity studies of aqueous mixed electrolyte solutions Authors: Patil, K J; Dhondge, S S; Manwatkar, S M Abstract: Relative viscosity studies of ternary aqueous mixed electrolyte solutions for the systems KBr-NaBr, KBr-Bu₄NBr, NaCI-NaBr and NaCI-Bu₄NBr at various constant ionic strengths with varying electrolyte mole fractions (y) at 25°C are reported. The data are used to calculate viscosity B-coefficients of the total electrolyte as a function of solute mole fraction. The excess viscosity B-coefficients (B^Ex) have been calculated and found to be distinctly positive for all the systems studied. The variation of B^Ex with y and the magnitudes have been explained in terms cation-cation, anion-anion interactions and the specific structural interactions with solvent water. Page(s): 950-953