Chapter 4
Polymerization of Water-Soluble Monomers in Microemulsions Downloaded by UNIV OF MISSOURI COLUMBIA on August 23, 2013 | http://pubs.acs.org Publication Date: December 30, 1989 | doi: 10.1021/bk-1989-0384.ch004
Potential Applications Françoise Candau Institut Charles Sadron, Centre de Recherches sur les Macromolécules, Ecole d'Applications des Hauts Polymères, 6 rue Boussingault, 67083 Strasbourg Cédex, France The general features of inverse microemulsion polymerization at the present state of knowledge are presented. The influence of various water-soluble monomers on the s t r u c t u r a l properties of the polymerizable microemulsions i s analyzed and an optimization of the process i s proposed. The best conditions correspond to the polymerization of monomers i n bicontinuous microemulsions characterized by very low i n t e r f a c i a l tensions, which subsequently leads to clear and stable microlatices of polymers with high molecular weights. The potential applications of the process are discussed. Polymerization i n microemulsion systems has recently gained some attention as a consequence of the numerous studies on microemulsions developed after the 1974 energy c r i s i s (1,2). This new type of polymerization can be considered an extension of the well-known emulsion polymerization process ( 3 ) . Microemulsions are thermodynamically stable and transparent c o l l o i d a l dispersions, which have the capacity to s o l u b i l i z e large amounts of o i l and water. Depending on the d i f f e r e n t components concentration, microemulsions can adopt various l a b i l e s t r u c t u r a l organizations globular (w/o or o/w tyoe), bicontinuous or even lamellar Polymerization of monomers has been achieved i n these d i f f e r e n t media (4-18). The f i r s t experimental studies aimed at elucidating the mechanism and the c h a r a c t e r i s t i c s of the process from an academic point of view. R e l a t i v e l y small amounts of monomers were dispersed i n microemulsions, which s t a b i l i t y was ensured by large surfactant concentrations. The major problem was often the onset of phase separation or polymer p r e c i p i t a t i o n i n the course of polymerization (7,8,15). This was due to some s t r u c t u r a l changes of these dynamic structures and to entropie effects associated with the polymerization. In some cases, these d i f f i c u l t i e s have been overcome 0097-6156/89Α)384-0047$06.00/0 * 1989 American Chemical Society
American Chemical Society Library
155 15th Structures; St., N.W. In Polymer1Association El-Nokaly, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. Washington, D.C. 20036
Downloaded by UNIV OF MISSOURI COLUMBIA on August 23, 2013 | http://pubs.acs.org Publication Date: December 30, 1989 | doi: 10.1021/bk-1989-0384.ch004
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P O L Y M E R ASSOCIATION STRUCTURES
as described i n our recent publications on the polymerization of acrylamide i n AOT reverse micelles (13,14). The main conclusions were that the mechanism and reaction k i n e t i c s i n inverse microemulsion polymerization are b a s i c a l l y d i f f e r e n t from those observed i n inverse emulsion. In addition, i t was shown that stable uniform microlatices (d
