Inverse suspension polymerization of sodium acrylate: Synthesis and characterization

Crosslinked Poly(acrylic acid) was synthesized by inverse suspension polyme rization. This process was investigated to determine the influence of diffe rent parameters like temperature, stirring speed, solution pH, and crosslin ker concentration and to obtain the best control of the kinetics. An aqueou s phase containing partially neutralized acrylic acid, crosslinking agent, and initiator agent was dispersed in an organic phase and stabilized by a s urfactant. The inverse suspension was carried out in heptane as the organic phase with a different ratio of neutralization of the monomer, different c rosslinker concentrations, and several stirring speeds. The polymerization was initiated by potassium persulfate (K2S2O8) with N-N'-methyleneloisacryl amide (MBA,) as the crosslinker and sorbitan monooleate as the surfactant. The influence of several parameters on the head size and the swelling capac ity was investigated. Particle diameters ranged from 10 to 130 mu m The kin etic results obtained by differential scanning calorimetry showed that conv ersion and polymerization rates are a function of the solution pH, and they fell when the concentration of the crosslinking agent was higher than 7.5% in the mass of MBA(C). (C) 2000 John Wiley & Sons, Inc.