Structure and properties of polyelectrolyte-surfactant nonstoichiometric complexes in low-polarity solvents

Solutions of complexes of poly(N-ethyl-4-vinylpyridinium) cations and dodecyl sulfate anions in chloroform are studied by viscometry, isothermal diffusion, flow birefringence, and dynamic light scattering techniques. Stoichiometric polyelectrolyte-surfactant complexes as well as nonstoichiometric ones with the compositions 0.55-1.0, expressed as the molar ratio of surfactant ions to the polycation chain units, neither form interchain associations nor dissociate into individual components in dilute solutions in chloroform. A decrease in the complexes' composition, i.e., a substitution of dodecyl anions with bromide anions, results in an increase of diffusion coefficients and a decrease in the intrinsic viscosity and in the absolute value of the negative segmental optical anisotropy of macromolecules of such complexes. Solubility of the studied complexes in low-polarity solvents increases in the order chloroform > chlorobenzene > benzene and decreases with decrease in the composition of complexes. Interchain associations dominate in dilute solutions of the complexes in chlorobenzene. Introduction of 1 vol % of cosolvent (methanol) to the dilute solutions of the complexes in chloroform and chlorobenzene (i) does not cause any change in the diffusion coefficient of the stoichiometric complex in chloroform, (ii) causes a decrease in the diffusion coefficient of the nonstoichiometric complexes in chloroform down to the value close to that of the stoichiometric complex, and (iii) causes an increase (more than an order of magnitude) in the diffusion coefficients of stoichiometric and nonstoichiometric complexes in chlorobenzene up to the values close to those of complexes in chloroform.