A facile CO2 switchable nanocomposite with reversible transition from sol to self-healable hydrogel

In this paper, we report a CO2/N-2-switchable sol to gel transition system based on a triblock copolymer of dimethylaminoethyl methacrylate (DMAEMA) and ethylene oxide (EO), with a measured composition DMAEMA(6)-EO109-DMAEMA(6), in aqueous nanoclay dispersions. LAPONITE (R) is exfoliated and stabilized by Pluronic F127. The aqueous mixture exhibits a strong response to CO2, changing from a low viscous sol to a self-healable gel. In the presence of CO2, the PDMAEMA blocks are protonated and the positive charged triblock copolymer bridge the negative charged nanoclays, formation of a physical network. As a consequence, a sol to gel transition is observed at the macro level. Upon removal of CO2 through bubbling with N-2, a corresponding gel to sol transition occurs due to the deconstruction of the physical network, which is a result of the departure of the deprotonated PDMAEMA blocks from the nanoclays. This sol to gel transition is fully reversible. Furthermore, the formed gel possesses excellent self-healing ability, meaning that this hydrogel is capable of autonomous healing upon damage. Thus, we believe the fundamentals of the present CO2-responsive smart hydrogel may hold promise for a wide range of areas, such as intelligent delivery systems and smart biomaterial fields, or a potential CO2 plugging agent for enhanced oil recovery (EOR) performed by CO2 flooding.