Martial Pabon

POLYMERIZABLE MICROEMULSIONS : SOME CRITERIA TO ACHIEVE AN OPTIMAL FORMULATION

Abstract Two types of water-soluble polymers have been prepared via a microemulsion polymerization route: (i) copolymers of acrylamide with sodium-2-acrylamido-2-methylpropanesulfonate and (ii) copolymers of acrylamide and sodium acrylate hydrophobically modified with an amphiphilic monomer. The formulation of the polymerizable microemulsions was optimized by using cohesive energy ratio (CER) and hydrophile-lipophile balance (HLB) concepts. In addition, the role played by the nature of the surfactants and the monomers was thoroughly investigated. The best formulation was obtained for high HLB values (8–11), in favor of microemulsions with a bicontinuous structure. The process was shown to yield remarkably stable, clear microlatexes of moderate particle size containing up to 25% high molecular weight polymer in the medium, in contrast to inverse latexes prepared by using classical emulsions which are unstable and turbid. These materials are of great interest for industrial applications.

Polymerization of acrylamide in solution and inverse emulsion: Number molecular weight distribution with chain transfer agent

The molecular weight distributions of the free-radical polymerization of acrylamide in solution and in inverse emulsion are examined as a function of concentrations of initiator and of amount of added chain transfer agent (sodium formate). When these distributions are displayed as In(number molecular weight distribution), readily obtained from the GPC trace (essentially by dividing by the square of molecular weight), the results can be semi-quantitatively interpreted in terms of the amounts of chain stoppage by transfer and by termination.