Specific ion effects of chloride vis-à-vis acetate, propionate and butyrate counterions on the cetylpyridinium headgroup at the micelle–solution and air–solution interfaces

Salting-in and salting-out effects of short amphiphilic molecules: a balance between specific ion effects and hydrophobicity

Salting-in or salting-out tendencies depend on a balance between headgroup-specific ion effects and the hydrophobicity of the tail.

Effect of Added Tetraalkylammonium Counterions on the Dilational Rheological Behaviors of N-Cocoyl Glycinate

Ion specific effect, which is also known as Hofmeister effect, has been reported in numerous systems including ionic surfactant aggregates. Acyl amino acid surfactants have attracted growing attentions in the field of novel surfactants research due to their environmentally benign characteristics. The objective of this study was to investigate the effect of different salts containing NH₄⁺ and tetraalkylammonium (TAA⁺), where alkyl = methyl (TMA⁺), ethyl (TEA⁺), and propyl (TPA⁺), cations on the dilational rheological properties of interfacial film are stabilized by potassium N-cocoyl glycinate (KCGl). The interfacial behaviors were studied using oscillating drop shape analysis method. The interfacial tensions (IFTs) and dilational rheological parameters results illustrate that KCGl in the presence of salts has better interfacial activity and stronger intermolecular interaction, indicating that added cations contribute to denser molecular packing at oil-water interface. Ion specific effects were observed in the system. Among the cations, KCGl shows highest dilational modulus in the presence of NH₄⁺. The overall interaction between cations and headgroups of KCGl decreases in the sequence NH₄⁺ >TMA⁺ >TEA⁺ ≈TPA⁺, which follows Hofmeister series. The increasing hydrophobicity of TAA⁺ prevents the interaction between cations and KCGl's headgroup, and therefore prevent amphiphiles from packing closely at interface. The results present a theoretical origin for useful application of KCGl in cosmetics, petroleum and daily chemical industries.

Kinetics and Mechanism of Alkaline Hydrolysis of N-(o-Aminophenyl)Phthalimide in the Presence and Absence of Cationic Micelles and Sodium Salts of Aliphatic Acids

Pseudo first-order rate constants, k obs, for the alkaline hydrolysis of N-( o-aminophenyl) phthalimide, obtained at constant [CTABr]T (total concentration of cetyltrimethylammonium bromide) and varying concentrations of inert salt MX (MX = sodium formate, sodium acetate, sodium propanoate, sodium butyrate, sodium valerate and sodium hexanoate) follow the relationship: [Formula: see text], where θ and KX/S are empirical constants and S = HO-. The values of KX/S for each aliphatic acid decrease with an increase in [CTABr]T. This relationship gives an empirical constant whose magnitude is the measure of the ability of an ion, X-, to expel another counterion S-, from the cationic micellar surface to the bulk aqueous phase. The values of the empirical constant, KX/S, are used to derive the ion exchange constant, KBrX.

Determination of Relative Counterion Binding Constant to Cationic Micelles

The efficiency of counterion affinity towards ionic micelles is often described in terms of the degree of counterion binding (β _X ) to ionic micelles or the conventional ion-exchange constant ([Formula: see text]) or relative binding constant ([Formula: see text]) of X ^- and Br^- counterions. This review describes the use of ionized phenyl salicylate ions, PSa^-, as a new probe to determine [Formula: see text] values using a semiempirical spectrophotometric method. The value of [Formula: see text] is found to be comparable to reported values obtained using different probes by the semiempirical kinetic method as well as different physical methods. Application of semiempirical methods for calculation of [Formula: see text] or [Formula: see text] values involves an inherent assumption that these values are independent of the physicochemical characteristics of the probe molecule.