ABSTRACT
In the current study, the association and phase separation of cationic tetradecyltrimethylammonium bromide (TTAB) and nonionic Triton X-100 (TX-100) surfactants with promethazine hydrochloride (PMH) were investigated in aqueous ammonium-based solutions. The micellization nature of the TTAB and PMH drug mixture was examined by evaluating critical micelle concentration (CMC) and counterion binding extent (ß) at different salt contents and temperatures (298.15-323.15 K). Micelle formation in the TTAB + PMH mixture was enhanced in the presence of ammonium salts, whereas the process was delayed with an increase in temperature in the respective salt solution. With an increase in salt content, the cloud point (CP) of the TX-100 + PMH mixture decreased, which revealed that the respective progression occurred through the salting out phenomenon. In micellization and clouding processes, the changes in free energies ΔG0m and ΔG0c were found to be negative and positive, respectively, demonstrating that the corresponding processes are spontaneous and non-spontaneous. Standard enthalpies (ΔH0m/ΔH0c) and standard entropies (ΔS0m/ΔS0c) for the association and clouding processes, respectively, were also calculated and discussed. The core forces amid TTAB/TX-100 and PMH in the manifestation of electrolytes are dipole-dipole and hydrophobic forces among the employed components according to the values for ΔH0m/ΔH0c and ΔS0m/ΔS0c, respectively.
ABSTRACT
The investigation of the micellization of a mixture of cetylpyridinium bromide (CPB) and levofloxacin hemihydrate (LFH) was carried out by a conductivity technique in aqueous and aq. additive mixtures, including NaCl, NaOAc, NaBenz, 4-ABA, and urea. The aggregation behavior of the CPB + LFH mixture was studied considering the variation in additive contents and the change in experimental temperature. The micelle formation of the CPB + LFH mixture was examined from the breakpoint observed in the specific conductivity versus surfactant concentration plots. Different micellar characteristics, such as the critical micelle concentration (CMC) and the extent of counter ion bound (ß), were evaluated for the CPB + LFH mixture. The CMC and ß were found to undergo a change with the types of solvents, composition of solvents, and working temperatures. The ΔG0m values of the CPB + LFH system in aqueous and aq. additive solutions were found to be negative, which denotes a spontaneous aggregation phenomenon of the CPB + LFH system. The changes in ΔH0m and ΔS0m for the CPB + LFH mixture were also detected with the alteration in the solvent nature and solution temperature. The ΔH0m and ΔS0m values obtained for the association of the CPB + LFH mixture reveal that the characteristic interaction forces may possibly be ion-dipole, dipole-dipole, and hydrophobic between CPB and LFH. The thermodynamics of transfer and ΔH0m-ΔS0m compensation variables were also determined. All the parameters computed in the present investigation are illustrated with proper logic.
ABSTRACT
Interactions between bovine serum albumin (BSA) and cetyltrimethylammonium chloride (CTAC) were studied utilizing conductivity approach. The critical micelle concentration (CMC), micelle ionization (α) along with counter ion binding (ß) of CTAC micellization in aqueous solutions of BSA/BSA + hydrotropes (HYTs) have been computed at 298.15-323.15 K. Increase in temperatures of CTAC + BSA/BSA mixtures in HYTs resulted in elevation of CMC due to the association of chemical species in the respective systems which reduced the degree of micelle formation. CTAC + BSA consumed greater extents of surfactant species to generate micelle formation in the corresponding systems at higher temperatures. Standard free energy change associated with the assembling processes of CTAC in BSA was found negative suggesting the spontaneous nature of micellization processes. Magnitudes of ∆Hm0 and ∆Sm0 obtained from CTAC + BSA aggregation revealed the existence of H-bonding, electrostatic interactions along with hydrophobic forces among the constituents employed in the respective systems. ∆Gm0 The estimated thermodynamic parameters of transfer (free energy (∆Gm,tr0), enthalpy (∆Hm,tr0) and entropy (∆Sm,tr0)) and compensation variables (∆Hm0,∗ and Tc) provided significant insights on the association behaviors of the CTAC + BSA system in the selected HYTs solutions.
