Aggregation and Rheology of a Triblock Supra-amphiphilic Polymer Prepared by Ionic Self-Assembly of a Double-Hydrophilic Polyelectrolyte with an Oppositely Charged Surfactant in Aqueous Solution

Supra-amphiphilic polymers as a kind of interesting and important supra-molecules have received considerable attention due to their unique advantages in preparation and promising applications in many areas. This work reported the solution aggregation and viscoelastic behavior of a triblock supra-amphiphilic polymer, which was fabricated by the ionic self-assembly of a triblock double-hydrophilic polyelectrolyte, poly(3-sulfopropylmethacrylate potassium salt)-b-poly(ethylene glycol)-b-poly(3-sulfopropylmethacrylate potassium salt) (PKSPMA-b-PEG-b-PKSPMA), with a cationic surfactant, dodecylamine hydrochloride (DAHC). The resulting supra-amphiphilic polymer contains a hydrophilic PEG middle block and two noncovalently linked hydrophobic end blocks, which are analogous to ABA-type triblock associative polymers (TAPs). Such a triblock supra-amphiphilic polymer has similar aggregation and rheological behavior to typical TAPs in aqueous solution. It can self-assemble into micelles and/or micellar aggregates in dilute solution and even form a clear physical gel in the concentrated solution by the bridging of polymer chains. However, it still exhibits some distinct rheological features from typical TAPs. Some factors such as the binding stoichiometry of oppositely charged groups and salt concentration have significant influence on its solution rheological properties. The solution relaxation dynamics follow the time–concentration/salt superposition and are dominantly controlled by the electrostatic interactions in the form of ion–ion pairs rather than the hydrophobic association in the core of a micelle. This work is the first time to report the solution rheological behavior of a supra-amphiphilic associative polymer. This result provides a new approach not only to the understanding of the solution rheology of the supra-amphiphilic associative polymers but also to the construction of a supramolecular viscoelastic gel.