Controllable Preparation of Polyacrylamide Hydrogel Microspheres in a Coaxial Microfluidic Device

A thermal-initiated polymerization procedure is described for the controlled preparation of monodispersed polyacrylamide (PAM) hydrogel microspheres. A coaxial microfluidic device was designed to disperse uniform drops (similar to 500 mu m) of acrylamide monomer aqueous solution into n-octane. Using a delay loop immersed into a heat bath, the polymerization is initiated and carried out in separate droplets. Combining the improvement of heat transfer in the microfluidic device and the sufficient addition of n-octane, the controllable preparation can still be achieved at 95 degrees C, much higher than 20-60 degrees C as reported prevalently. Herein, the PAM microspheres can be prepared within 2 min or less, with the CV of diameter less than 4%. Furthermore, based on this controllable reaction platform, PAM microspheres were prepared at various reaction temperatures (higher than 90 degrees C) and monomer solution compositions to investigate the fundamental rules of controlling on their skeleton structure and absorbent capacity in deionized water.