Surface properties and micellization in aqueous solutions of homologous series of cationic surface-active monomers

The surface and bulk properties of aqueous solutions of homologous series of cationic surface-active monomers (SAM), derivatives of dimethylaminoethyl methacrylate, were extensively studied in connection with the development of the colloidal basis of the nanoencapsulation technology of biologically active substances. Surface tension isotherms σ(C) at the air-water interface within the temperature range of 25 - 55°C, isotherms of the differential refraction index Δn(C), density p(C), and molar heat capacity C p (C) at 25°C were measured. Standard values of a free energy, entropy and enthalpy of adsorption and micellization as well as values of the increments of the free energies of adsorption (1.2 kJ/mol) and micellization (1.5 kJ/mol) per one CH 2 -group were determined for the SAM studied. Degree of bonding of counterions by the SAM micelles (β = 0.98) were calculated using surface tension isotherms. Isotherms of the apparent variation of solution density Δp(C) were calculated in the approximation of additive contribution of various components of SAM solutions to the specific refraction. The values of the increments of molar heat capacities C p per one CH 2 -group (equal to 13 - 25 J/mol) were found to be in fair agreement with the calculated ones [24].