Acrylamide/2-acryloxyethyltrimethyl ammonium chloride copolymers in inverse microemulsion, with a cationic charge density of 60% and a concentration of active matter of 30 wt %, of interest as flocculants have been obtained by inverse microemulsion copolymerization. Interesting inverse microemulsion formulations from both industrial and economical standpoints were selected from pseudoternary phase diagrams. These formulations were polymerized by semicontinuous free radical copolymerization in inverse microemulsion using sodium disulfite and ammonium persulfate as initiators. Influence of initiators and initiator addition conditions (specific flow rate and concentration) on semicontinuous polymerization and final product properties as flocculants have been studied. A strong difference in copolymer solution viscosity has been found when an aqueous solution of sodium disulfite is used as initiator instead of sodium disulfite/ammonium persulfate couple redox, specially for low sodium disulfite solution feeding flow. (c) 2006 Wiley Periodicals, Inc.