Effect of water solubility of monomer on reaction kinetics oil-water microemulsion copolymerisation

A partially water soluble monomer acrylonitrile (AN) and a hydrophobic mono mer butyl acrylate (BuA) were copolymerised in oil-water microemulsions pre pared with anionic emulsifier sodium dodecyl sulfate. The effect of initiat or type and concentration, polymerisation temperature, monomer feed composi tion and cosurfactant concentration on kinetics was investigated. Stable an d translucent latexes were obtained. Rate of polymerisation (R-p) was found higher for water-soluble initiator potassium persulfate than for oil-solub le initiator 2,2,azo-bis-isobutyronitrile, R-p was observed to be directly proportional to the initiator concentration and BuA concentration in feed w hereas it was inversely proportional to the AN concentration in feed. The p article size was found dependent on the initiator type, polymerisation temp erature and monomer feed composition. The overall energy of activation (<(D elta)over bar>E-a) was found to be dependent on the initiator type. The dec rease in thr percentage conversion and R-p and increase in the particle siz e was observed with increasing cosurfactant (hexanol) concentration. The la texes were characterised by dynamic light scattering and transmission elect ron microscopy for particle size. Latex particles were found to contain mac romolecules of 10(5) molecular masses with polydispersity 1.6. (C) 1999 Els evier Science Ltd. All rights reserved.