Frontal polymerization for smart intrinsic self-healing hydrogels and its integration with microfluidics

Frontal polymerization (FP) is applied for the synthesis of β-cyclodextrin/poly(vinylimidazole-co-N-vinylcaprolactam-co-acrylic acid) (β-CD/P(VI-co-NVCL-co-AA)) copolymers. The dependence of frontal velocity and temperature on the initiator and cross-linker are discussed. The synthesized copolymers have been characterized by Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The thermo-pH dual-stimuli responsive behavior of the hydrogel is determined by swelling measurement at different temperatures and pH values. Besides, the hydrogels show intrinsic self-healing behavior and their healing efficiency is determined by the mechanical tests. Interestingly, we integrate FP with microfluidic technology, which may realize the execution of FP under continuous condition. Such simple microfluidics-FP integrated approach has both methodological and practical value for the synthesis of functional materials. This paper mainly presents the synthesis and characterization of β-cyclodextrin/poly(vinylimidazole-co-N-vinylcaprolactam-co-acrylic acid) (β-CD/P(VI-co-NVCL-co-AA)) copolymers by using thermal frontal polymerization (TFP). Hydrogels were found to be self-healing with good mechanical performance and show dual thermo-pH responsive behavior. Low-cost, energy-saving and efficient method of thermal frontal polymerization process was integrated with microfluidics technology to prepare supraball hydrogel.