ИСТИНА

Interpolyelectrolyte complexes (IPECs) resulting from the electrostatic interaction between oppositely charged macromolecules are of considerable interest not only from a fundamental point of view but also because of their numerous promising potential applications as new intelligent polymeric reagents and materials for industry. ecology, biotechnology and medicine. Micelles of ionic amphiphilic block copolymers are also naturally expected to take part in interpolyelectrolyte complexation. Up to the date, however, the interaction of such macromolecular assemblies with oppositely charged polyelectrolytes has received only little attention. Our contribution considers the interaction of micelles generated in aqueous solutions of polyisobutylene-block-poly(sodium methacrylate) diblock copolymers (PIB(20)-b-PMANa(X), subscripts denote number-average degrees of polymerization of the corresponding blocks X = 100, 280, 425) with a strong cationic polyelectrolyte poly(N-ethyl-4-vinylpyridinium bromide) (PVPEtBr, DPw = 500) and describes properties of IPECs resulting from this interaction. On addition of the solution of PVPEtBr to alkaline solutions of the PIB(20)-b-PMANa(X) micelles (pH = 9), no phase separation is observed until the charge ratio of the polyelectrolytes, Z = [+]/[-], exceeds a certain value, Z*. The values of Z* were found to be in the range 0.4 ÷ 0.6, being dependent on the length of the PMANa block and the concentration of NaCl. At Z < Z*, the mixtures of the oppositely charged polymeric components remain homogeneous. Such homogeneous mixtures were examined by means of analytical ultracentrifugation, dynamic light scattering, fluorescence spectroscopy (with the use of pyrene as a polarity probe), and small-angle neutron scattering. The obtained results suggest that the PIB(20)-b-PMANa(X) micelles interacting with PVPEtBr form a novel type of water-soluble IPECs in which the polyelectrolyte component of the original micelles apparently plays a lyophilizing part. Each particle of the formed water-soluble IPECs is considered to be a peculiar onion-like micelle consisting of a two-phase hydrophobic nucleus and a hydrophilic corona. The nucleus consists of a polyisobutylene core surrounded by a shell of coupled oppositely charged polyelectrolyte fragments. The corona is built up from fragments of PMANa blocks not involved in the interpolyelectrolyte complexation. At relatively high ionic strength ([NaCl] > 0.45 M), the electrostatic interaction between the PIB(20)-b-PMANa(X) micelles and PVPEtBr was found to be suppressed because of the screening effect of low molecular weight ions: dissociation of the micellar IPECs to their original polymeric components was observed. Interpolyion exchange reactions proceeding upon addition of PMANa (DPn = 400) to solutions of the formed micellar IPECs were examined by means of analytical ultracentrifugation. A transfer of a certain fraction of cationic macromolecules from the water-soluble complex species to free chains of PMANa was demonstrated to be a result of such reactions.