The effects of temperature on the critical micelle concentrations of alkyl α-picolinium bromides

Abstract

The temperature dependence of the critical micelle concentrations of decyl, dodecyl and tetradecyl a-picolinium bromides has been determined by measurement of conductance. Constants for the equation relating log. CMC and alkyl chain length have been calculated for the temperature range 5" to 70", in increments of 5". An estimate of the effect of temperature upon the degree of counterion binding is recorded. Thermodynamic parameters have been calculated using the uncharged phase-separation model and a theoretical interpretation of the process of micellization given.

Effect of Hydrophobic Chain Length of Surfactants on Enthalpy−Entropy Compensation of Micellization

“…The minimum cmc is generally observed not only in nonionic surfactants but also in ionic surfactants. Table also lists the values of T min determined from cmc data available in literature for various homologous series of ionic surfactants. ,− , It is consistently found that for surfactants in a homologous series T min is smaller for surfactants of longer alkyl chain length. An increase of hydrophobicity by replacing one of the methyl groups of dodecyltrimethylammonium bromide by a benzyl group to form dodecylbenzyldimethylammonium bromide would reduce the T min from 21 to 18 °C.…”

“…Only some of the experimental data of the temperature of minimum cmc, T min , have been reported and discussed in the literature. , There is, to the best of our knowledge, no systematic study on the relation between T min and the molecular structure of the surfactants. On the basis of our experimental cmc data 14 and the available data in the literature, ,− the dependence of T min on surfactant hydrophilic−lipophilic balance is discussed in section III. In section IV, the cmc data treatment of determining Δ G ° m , Δ H ° m , and Δ S ° m is described for both nonionic and ionic surfactants.…”

“…In addition, it is intriguing to note that the intercept Δ H * m is a linear function of the hydrophobic chain length of the surfactant. We further examined the available cmc data of ionic surfactants in the literature. ,,− The intercept Δ H * m of compensation lines is also found as a function of hydrophobic chain length of surfactant for several homologous series of ionic surfactants in aqueous solutions.…”

Wide-Antimicrobial Spectrum of Picolinium Salts

“…Picolinium salts have, in many cases, been used as intermediates for the preparation of donor-acceptor molecules for the construction of promising photo- and electro-active materials [ 29 , 32 , 33 , 34 , 35 , 36 , 37 , 38 ]. In addition, their typical physicochemical features such as surface activity and micellization have been intensively studied in the line of their possible application [ 39 , 40 , 41 , 42 , 43 , 44 ]. For instance, N -( n -hexadecyl)- and N -( n -heptadecyl)-3-methylpyridinium bromide or 1-methyl-3-octylpyridinium alkyl sulfate were found to be effective for micelle-based drug delivery to improve drug solubility and the bioavailability of anionic drugs and metal complexes [ 28 , 43 ].…”

Heat Evolution of Micelle Formation, Dependence of Enthalpy, and Heat Capacity on the Surfactant Chain Length and Head Group

“…In an attempt to evaluate the generality of our interpretation of the temperature dependence of H demic , we have reanalyzed the published data regarding the dependence of H demic on temperature for a few series of surfactants of a common head group and varying chain length (11,(23)(24)(25)(26)(27). Unfortunately, much of these data are of limited precision due to limitations of experimental tools available until recently (37,38).…”