ИСТИНА

Managing the association of amphiphilic copolymers in aqueous media is a key point in development of a broad spectrum of advanced materials including thickening agents, drug delivery systems, nanoreactors, smart membranes, protective and electroconductive films and coatings [1]. In our research we have synthesized and explored a novel type of ABC-amphiphilic copolymers, where a central hydrophobic C-block (poly-n-butyl acrylate, PBA) is surrounded by a couple of A-st-B blocks from nonionic hydrophilic A-units (N-isopropylacrylamide, NIPAM) and ionic hydrophilic B-units (acrylic acid, AA). The copolymers were synthesized via RAFT-polymerization, dissolved in dimethylformamide (nonselective solvent), transferred into pure water using dialysis technique and tested by dynamic light scattering. The molecular mass of PBA-block was 9000 (polymer I) and 32700 (polymer II). In both copolymers cumulative molecular mass of two NIPAM-st-AA blocks equals 4600, the molar ratio NIPAM:AA is 50:50 [2]. Two factors in aggregative behavior of ABC-copolymers can be isolated. The first one is enhanced shielding capacity of a pair of hydrophilic blocks. Thus at room temperature and neutral pH polymer I exists in a form of single macromolecules, while micelles do form only for polymer II with more extended hydrophobic block. The second is the strong tendency for intermolecular/intermicellar association of NIPAM-st-AA blocks in aqueous solution. Such association monotonously increases with the growth of temperature and passes through a minimum as a function of pH. For example, the dimensions of intermicellar associates for polymer II are maximum in acid media (Rh ~ 400 nm), minimum at neutral pH (Rh ~ 100 nm) and increase again in alkaline media (Rh ~ 200 nm). Overall, by changing the molecular mass of PBA-block, pH and temperature one can effectively manipulate the aggregation behavior of amphiphilic (A-st-B)-b-C-b-(A-st-B) copolymers, getting whole range of block-copolymer structures from single coils through individual micelles to intermicellar associates. Acknowledgements The Russian Science Foundation is acknowledged for support under grant No 15-13-30007. References 1. Forster S., Plantenberg T. // Angew. Chem. Int. Ed., 2002, 41(5), P. 688. 2. Chernikova E.V., Plutalova A.V., Mineeva K.O., Vishnevetskii D.V., Lysenko E.A., Serkhacheva N.S., Prokopov N.I. // Polym. Sci. Ser. B, 2016, 58(5), P. 564.