Mixed micellization between amphiphilic drug propranolol hydrochloride and cetyltrimethylammonium bromide surfactant in aqueous medium

The interaction between an amphiphilic drug (propranolol hydrochloride (PPL)) and cationic surfactant (cetyltrimethylammonium bromide (CTAB)) in aqueous solution has been investigated at different mole fractions. The CMC (pure and mixture), mixed micellar composition (X-1(id), X-2(id), X-1(m) and X-2(m)), interaction parameter (beta(m)) and the degree of counterion binding (alpha) have been computed and discussed. The micellar interaction parameter (the (beta(m)-parameter) was determined from the CMC values of the pure drug and surfactant (CMC1 and CMC2) and the mixed system (CMCmix) using the Rubingh's model (regular solution theory). For all mixtures of PPL/CTAB, the results indicate a fairly strong attractive interaction (negative (beta(m)-values), which confirming synergistic interactions between drug-surfactant. Also, activity coefficients (f(1)(m) and f(2)(m)) are always less than unity suggesting non-ideality in the mixtures. Finally, the standard Gibbs energy of micellization (Delta G(mic)(degrees)) and the excess free energy of micellization (Delta G(mic)(ex)) values were evaluated and discussed with increasing drug concentration. (C) 2017 Published by Elsevier B.V.