ИСТИНА

Surfactant molecules are able to self-assemble into long wormlike micelles, which behave like reversibly breakable polymers. In particular, they can form entangled networks exhibiting viscoelasticity. In the present paper, we propose to enhance the rheological properties of the micellar networks by adding polymer network. In order to retain the labile character of hydrogels, polymer chains were cross-linked by dynamic bonds, which are able to reversibly break and recombine. Wormlike micellar network was prepared by using mixed anionic (potassium oleate) and cationic (n-octyltrimethylammonium bromide) surfactants, while dynamic polymer network consisted of polyvinyl alcohol (PVA) cross-linked by borate ions. Interpenetrating networks were obtained by a simple one-pot method, and both networks were formed by self-assembly [1]. Two-component hydrogels show a synergistic enhancement of rheological properties as compared to single polymer and micellar networks: a 3400-fold increase of viscosity and 27-fold rise of the plateau storage modulus. As proven by structural investigations by SANS, USANS and cryo-TEM, this is due to the microphase separation leading to local concentrating of PVA and wormlike micelles providing larger number of polymer-polymer contacts for cross-linking and longer micelles with more entanglements. SANS data confirm that local cylindrical structure of the micelles is not affected by the presence of polymer, while 11B NMR shows that PVA chains remain cross-linked into a network in the presence of wormlike micelles. The strongest enhancement in rheological properties was observed when the volumes of both microphases are rather close to each other providing the conditions for the formation of bicontinuous microphase separated structure, so that each of the components can spread in the whole volume of the system. When the amount of one of the components becomes predominant, the synergistic effect vanishes. Two-component dynamic hydrogels obtained in this work are very promising for the application in many areas, ranging from enhanced oil recovery to biomedical uses. Acknowledgment: The work was financially supported by the Russian Science Foundation (project 19-73-20133).