ИСТИНА

The self-assembly of ionic amphiphilic diblock copolymers polyisobutylene-block-poly(sodium methacrylate) containing 20 monomer units in polyisobutylene block and 100, 280, or 425 monomer units in poly(sodium methacrylate) (PMANa) block was examined in alkaline media by means of fluorescence technique with a use of pyrene as a polarity probe. For all the copolymers, the increase in their concentration above the certain value (cmc) was found to result in the formation of macromolecular micelles. The values of cmc were found to be about 1E-06 mole/L (cmc is given as the concentration of macromolecules), they being nearly independent of the length of PMANa block of the copolymers and ionic strength of the surrounding medium ([NaCl] ≤ 0.5 M). The hydrodynamic characteristics of such copolymer assemblies were determined by means of analytical ultracentrifugation. The images obtained with transmission electron microscopy provided evidence for a virtually spherical shape of the macromolecular micelles. The interaction between the copolymer micelles and cationic polyelectrolytes, poly(N-ethyl(amyl)-4-vinylpyridinium bromide) with DPw = 500 and 2,5-ionene bromide with DPw = 60, in alkaline media was examined by means of turbidimetry, fluorescence spectroscopy (pyrene was used as s fluorescent probe), and analytical ultracentrifugation. In mixtures containing charges of the polymeric components in non-equivalent ratios Z = [+]/[-] lower than the certain critical value Z < Z* < 1, the formation of particles of water-soluble non-stoichiometric interpolyelectrolyte complexes considerably enriched by carboxylate groups of the anionic copolymers compared to ionic groups of the cationic polyelectrolyte was observed. Such particles were found to effectively solubilize pyrene, their solubilization capability being nearly the same as for the pure macromolecular micelles. A particle of the interpolyelectrolyte complex resulting from the interaction of the copolymer assemblies with cationic macromolecules was hypothesized to be a peculiar micelle consisting of a hydrophobic nucleus formed by a polyisobutylene core surrounded by a layer of coupled oppositely charged polyelectrolyte fragments and an ionic corona formed by fragments of PMANa blocks not involved in interpolyelectrolyte interaction. The dependencies of Z* on the concentration of NaCl were obtained for all the copolymers as well as for a reference anionic homopolyelectrolyte PMANa. While for PMANa the increase in the salt concentration is accompanied by a drastic decrease in the values of Z*, this tendency was either completely absent or only slightly detectable for the copolymers. For all the copolymers, the interaction between the copolymer micelles and the cationic polyelectrolytes was found to be completely suppressed at relatively high salt concentrations due to screening effect of small ions, stability of micellar interpolyelectrolyte complexes with respect to their salt-induced dissociation being close to that observed for interpolyelectrolyte complexes formed by the corresponding homopolyelectrolytes.