The influence of monomers upon microemulsions with short chain cosurfactant

Several monomers (i.e., acrylonitrile (ACN), ethyl acrylate (EtA), acrylate of 2 ethylhexyl (EHA), butyl acrylate (BuA), vinyl acetate (VAc), methyl m ethacrylate (MMA) and styrene (St)) were investigated in order to study the ir capacities to form microemulsions. The surfactant was nonyl phenol ethox ylate with 25 moles ethylene oxide and ethanol was used as the cosurfactant . The phase diagrams prove that the capacity for microemulsion formation va ries in the following sequence: ACN = EtA > VAc > BuA > MMA > St > EHA. Con ductometric and rqfractometric studies allowed us to evidence the formation of microemulsions with W/O, bicontinuous or O/W structure. Fluorescence st udies give interesting informations on the stabilization capacity of the mo nomers dispersed by interaction with hydrophobic chain of the cosurfactant. H-NMR studies suggest that the monomers in microemulsions lie in regions w ith various polarities as junction of their chemical nature. In polymerizat ion initiated with benzoyl peroxide the minimum conversions were obtained i n zones of composition where the initial microemulsions possess a bicontinu ous microstructure. The reactions of degradative transfer of the increasing macroradicals account for these conversion modifications. For initiation w ith ammonium persulphate, its rate of decomposition depends on its ability to displace the proton bonded to the substituted vinylic carbon of the mono mer. The productivity of this initiator varies within the sequence MMA > Et A > BuA > St > ACN > VAc. The consumption of the initiator, as induced by t he monomer, depends on its chemical nature and on the solubilization site o f the microemulsions.