ИСТИНА

Properties of ionic amphiphilic diblock copolymers containing polystyrene PS as a non-polar block and the alternating copolymer of styrene and maleic acid (in the form of its sodium salt) P[S/MaNa] as a hydrophilic block, PS(X)-b-P[S/MaNa](Y) (X, Y are DPns of the corresponding blocks, X = 20, Y = 145; X = 155, Y = 75; X = 210, Y = 70) in aqueous alkaline solutions (pH 9.5) were examined by means of analytical ultracentrifugation, dynamic small-angle light scattering, and fluorescence spectroscopy (with the use of pyrene as a polarity probe). The copolymers with the longer non-polar blocks were found to undergo self-assembly, generating large aggregates with high values of hydrodynamic radius Rh and sedimentation coefficient S: e.g., at 0.1 M NaCl Rh = 30 nm, S = 45 Sv and Rh = 55 nm, S = 90 Sv for PS(155)-b-P[S/MaNa](75) and PS(210)-b-P[S/MaNa](70), respectively. Such aggregates were shown to effectively solubilize pyrene, manifesting their micellar structure. For the copolymer with the short non-polar block, the values of Rh and S under the same conditions are small, Rh = 8 nm and S = 2 Sv, and comparable with those detected for the reference alternating copolymer P[S/MaNa](120), thus indicating that PS(20)-b-P[S/MaNa](145) exists in the aqueous alkaline solutions in molecularly dispersed state. The interaction of PS(X)-b-P[S/MaNa](Y) with the strong linear cationic polyelectrolyte, poly-N-ethyl-vinylpyridinium bromide P4VP*EtBr (DPw = 480), in aqueous alkaline media (pH 9.5) was examined by means of turbidimetry. In the case of the copolymers with the longer non-polar blocks, this interaction was demonstrated to result in the formation of insoluble interpolyelectrolyte complexes (IPECs) only (most probably because of the pronounced hydrophobicity of original copolymer molecules, resulting from the high molar content of styrene monomer units x in such copolymers, x = 75 - 80%) while the copolymer with the short non-polar block (x = 53%) was found to generate water-soluble IPECs with P4VP*EtBr when the charge ratio Z in the system, Z = [+]/[-] (molar concentrations of the ionic groups of the corresponding polymeric components are given in the brackets), does not exceed a certain critical value of Z*, Z < Z* = 0.2 (0.2 M < [NaCl] < 0.7 M). The interpolyelectrolyte complexation between PS(X)-b-P[S/MaNa](Y) and P4VP*EtBr was shown to be suppressed at rather high ionic strength of the surrounding medium due to the screening effect of small ions, the concentration of NaCl required for the dissociation of IPECs was found to considerably increase with the rising x, changing from ca 0.75 M for PS(20)-b-P[S/MaNa](145) (x = 53%) up to ca 1.1 M for PS(210)-b-P[S/MaNa](70) (x = 80%).