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.

The stoichiometric complexes of the DNA samples of rather different molecular masses:  300−500 b.p. (DNA1) and 5000−10000 b.p. (DNA2) with dodecyldimethylammonium (DODA) chloride as a cationic amphiphile were prepared. DNA1−DODA and DNA2−DODA complexes are soluble in low polar organic solvents, in particular, in chloroform, as well as the complexes of ordinary linear polyelectrolytes with micelle-forming ionic surfactants. The solution behavior of the DNA−DODA complexes was studied by ultracentrifugation, viscometry, isothermal diffusion, and electrical birefringence techniques. It has been found that the DNA−DODA complex species in their dilute solutions in chloroform and a chloroform−acetone mixture (2:1) are represented by individual complex macromolecules retaining a double spirality, but strongly compacted. The latter is contrasting with other polyelectrolyte−surfactant complexes, which behave in chloroform as in a good solvent, taking expanded random coil conformations. The possible reason of such a basic difference is discussed and considered to be the result of an inherent tendency of the DNA double helix to be compacted if not ionized. This tendency has been detected due to a unique compromise between the thermodynamic solubility and complete electric neutrality of DNA−surfactant complex macromolecules in low polar organic solvent.

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