Synthesis and characterization of thermally-responsive hydroxypropyl methylcellulose gel beads

Thermally responsive gels of hydroxypropyl methylcellulose (HPMC) were produced in spherical form by a suspension crosslinking technique. The suspension crosslinking of HPMC with divinylsulfone was accomplished by dispersing aqueous polymer droplets, containing all of the reactants, in a continuous organic phase. The gel beads were characterized in terms of their swelling properties and particle size distribution. The swelling degrees at 25°C of different formulations of the gel beads ranged from 12 to 123 times their dry volume and shrank to 4 to 18 times dry volume at 75°C. The spherical beads were made in diameters ranging from 500 to 3000 μ. Bead size generally decreased with use of a larger impeller, suspending at high stirring speeds, or at a lower phase ratio. As bead size decreased, the size distribution also narrowed. When compared with bulk HPMC gels, the gel beads demonstrated the same swelling properties and crosslinked network formation.