Generation of Monodispersed Spherical Thermosensitive Gels and Their Swelling and Shrinking Behaviors in Aqueous Polymeric Solutions

This study investigates the factors affecting the formation of monodispersed thermosensitive gels and the parameters influencing the movement of gel particles containing N-isopropyl acrylamide in an aqueous polymeric solution in an upper heating system. Monodispersed thermosensitive gels were generated, and their swelling and shrinking behaviors were observed. The results revealed that continuous-phase flow rate and kinematic viscosity were most influential on the size of the monodispersed thermosensitive gels, which exhibited swelling and shrinking at both low and high temperatures of the polymeric aqueous solution, respectively, and demonstrated negative thermal expansion. In a low-temperature solution, the buoyancy force acting on the gel particles exceeded the gravitational force, because of which the size of the gels increased and the gels to ascended. At higher temperatures, the gels shrank because the gravitational force outweighed the buoyancy force, causing the gels to descend. The gels with a larger diameter tended to have longer durations of vertical movements within the aqueous polymeric solution than the smaller-sized gels; moreover, equilibrium conditions were quickly achieved by the smaller gels.