ИСТИНА

The interaction of star-shaped poly(acrylic acid) (PAA)N with the number of arms N = 8 (DPn(arm) ≈ 100) with the double hydrophilic ionic/nonionic diblock copolymer poly(N-methyl-2-vinylpyridinium methylsulfate)-block-poly(ethylene oxide) (P2VPQ(38)-b-PEO(211), where subscripts denote DPn of the corresponding blocks) in aqueous media at pH 7 and 0.1 M NaCl (DN(PAA) = 0.9) was examined. Aqueous mixtures of (PAA)8 and P2VPQ(38)-b-PEO(211) were found to remain homogeneous for any value of the ratio between amounts of the ionic groups of the polymeric components, Z (Z = [N+]/[COO- + COOH]), which is in striking contrast to the reference system, aqueous mixtures of (PAA)8 and poly(N-methyl-2-vinylpyridinium methylsulfate) (P2VPQ, DPn = 36) that undergoes phase separation when Z exceeds the certain threshold value. Dynamic light scattering carried out for such homogeneous mixtures of (PAA)8 and P2VPQ(38)-b-PEO(211) provides evidence on bimodal distribution of apparent hydrodynamic radius Rh(app) of the formed macromolecular co-assemblies, though the fraction of the larger co-assemblies is rather low. The smaller macromolecular co-assemblies constituting a dominant fraction are considered as particles of the water-soluble interpolyelectrolyte complex formed upon the interaction of (PAA)8 and P2VPQ(38)-b-PEO(211). Their hydrodynamic radii (13 ÷ 15 nm) are rather close to the hydrodynamic radius of the corresponding individual (PAA)8 stars (= 8 nm), even at the charge balance (Z = 1) between the oppositely charged polymeric components, thereby suggesting that each of the complex species comprises only one macromolecule of (PAA)8. The formed macromolecular co-assemblies are thought to have "core-corona" (micellar) structure with a rather hydrophobic core assemblied from the coupled oppositely charged polyelectrolyte fragments and a hydrophilic corona providing solubility of the whole complex species in aqueous media. The corona of such water-soluble complex species is discussed to be either a two-component corona built up from the ionic arms of (PAA)8 and the non-ionic PEO blocks which maybe either mixed or segregated or a one-component corona formed only by the non-ionic PEO blocks.