A Mathematical Approach to a More Accurate Determination of Critical Micelle Concentration and Other Thermodynamic Parameters of 14‐2‐14 Gemini Surfactant in Water–Organic Solvent Mixed Media at Variable Temperatures

Abstract

To explore how the solvent characteristics influence the self-aggregation of the cationic gemini surfactant dimethylene-1,2-bis(tetradecyldimethylammonium bromide) (14-2-14) and to obtain various energetic parameters, conductometric experiments were performed on the binary mixtures in the presence of commonly used organic solvents; formamide (FA), acetonitrile (AN) and 2-methoxyethanol (ME) in aqueous solutions at varying temperatures (298.15-323.15 K) and compositions. The procedure suggested by Carpena et al. has been utilized to analyze conductivity-concentration plots in order to obtain critical micelle concentration (CMC) and degree of counterion dissociation (a) of the micelles. This method provides more accurate results as compared to conventional treatments, and the experimental error for the evaluation of micellar parameters is reduced significantly. The results revealed that, although the process of micellization becomes less favorable with the increase in composition of FA, AN and ME in mixed systems, the increase in CMC at compositions lower than 20% (v/v) of the organic solvents is relatively less, indicating that water character is dominant in the bulk phase. As the enthalpy of micellization became more negative, the corresponding entropy change became less positive and enthalpy-entropy compensation phenomenon has been observed for 14-2-14 in all the mixtures within the studied temperature range.

Surfactant Self-Assembling and Critical Micelle Concentration: One Approach Fits All?

“…Actually, different mathematical approaches have been applied to calculate CMC from the experimental data obtained from different techniques ( e.g ., a linear regression model for tensiometry, a nonlinear regression model for spectrofluorimetry). 17 − 19 In addition, different approaches have been proposed for the same technique, showing sometimes only partially advantages over each other. 20 , 21 We proposed here the use of a single approach, as the second derivative of the experimental data from different techniques (tensiometry, conductimetry, densimetry, spectrofluorimetry, and high-resolution ultrasound spectroscopy) to determine the CMC values.…”

“…Despite different techniques generally provide quite comparable CMC values among the tested surfactants, it is not unequivocal and straightforward how to treat the experimental data to calculate the CMC values. Actually, different mathematical approaches have been applied to calculate CMC from the experimental data obtained from different techniques ( e.g ., a linear regression model for tensiometry, a nonlinear regression model for spectrofluorimetry). − In addition, different approaches have been proposed for the same technique, showing sometimes only partially advantages over each other. , We proposed here the use of a single approach, as the second derivative of the experimental data from different techniques (tensiometry, conductimetry, densimetry, spectrofluorimetry, and high-resolution ultrasound spectroscopy) to determine the CMC values. As such, five different surfactants were chosen as a model, specifically, three anionic (sodium dodecyl sulfate, sodium deoxycolate, and N -lauroyl sarcosinate) and two nonionic, such as polyethylene glycol (PEG) ester surfactants (polyethylenglicol (8) monostearate and polyethylenglicol (8) monolaurate).…”

Construction of MPEG‐PCL Nanomicelle Ocular Drug Delivery Vector and Its Application in the Treatment of Hypertensive Fundus Disease

“…The polymer material is vacuum dried in advance. Take about 200 mg of potassium bromide (KBr) and use a grinding rod to fully grind into ultrafine powder, weigh 2 mg of the sample to be tested and potassium bromide to fully grind and mix, and then make it into potassium bromide tablets for detection by infrared spectroscopy [33][34][35][36].…”