Inverse-emulsion copolymerization of acrylamide and quaternary ammonium cationic monomers with block copolymeric surfactants: copolymer composition control using batch and semi-batch techniques

Abstract

An experimental investigation of the inverse-emulsion copolymerization of acrylamide and quaternary ammonium cationic monomers (dimethylaminoethylacrylate, DMAEA and dimethylaminoethylmethacrylate, DMAEM) has been carried out using both a block copolymeric surfactant (HB246) whose hydrophilic moiety is polyethylene oxide and whose hydrophobic moiety is poly(12 hydroxy stearic acid) and sorbitan monoleate (SMO). Our results indicate that the choice of surfactant influences strongly the quality of the copolymers produced. For example, more uniform copolymers of acrylamide and DMAEA can be synthesized using the block copolymeric surfactant (HB246) at faster production rates in comparison with sorbitan monoleate (SMO) when utilizing batch reactors. However, a composition drift is observed in the inverse-emulsion copolymerization of acrylamide and DMAEM using HB246. A possible explanation for this behaviour is either a reduced reactivity ratio ( r 2) or propagation constant ( k 22). However, physical effects such as a possible lower interfacial acrylamide concentration are not to be ruled out. It is also shown, for the first time, that copolymers of acrylamide and DMAEM of more uniform composition can be produced by implementing simple semi-batch policies with non time-varying feedrates. It is believed that these cationic copolymers would have a higher flocculation efficiency both in municipal and in industrial water treatment due to their more uniform distribution of the positive charge along the polyacrylamide backbone.