THE PROPERTIES OF AQUEOUS-SOLUTIONS OF SOME SHORT-CHAIN COSURFACTANTSUSED FOR RADICAL POLYMERIZATION OF VINYL-ACETATE

The refractive index and excess molar volume, of the following short h ydrocarbon chain cosurfactants were studied: ethylene glycol, ethylene glycol monomethyl ether, ethanol, n-, i-propanol, acrylic acid, ethyl monomethylmaleate and acrylamide. The refractive indexes of the aqueo us solutions of these compounds vary nonlinearly with composition. The maximum variation of refractive indexes occurs up to a cosurfactant/w ater molar ratio equal to 1/5. The fluorescence probe method was succe ssfully used to evidence the structure modifications of the alcohol-wa ter mixtures. The intensity ratio of pyrene fluorescence vibrational b ands varies nonlinearly with the composition of the systems; in case o f l-propanol, the sudden decrease of the ratio is similar to that of m icellar solutions, so that a critical concentration of association can be determined at a 0.88 water mole fraction. It was shown, in good ag reement with data in literature, that the compounds mentioned penetrat e into the cluster structure of water and associate. At concentrations higher than critical, restructuring of aqueous solutions continues an d structures of bicontinuous or w/o type may arise. The excess volume of the first six compounds is negative owing to the restructuring just mentioned. Vinyl acetate may penetrate in the structures of binary sy stems to form homogeneous systems. The number of homogeneous systems d ecreases in the sequence: ethanol, i-propanol, acrylic acid, n-propano l, the monomethylether of ethyleneglycol, methyl monomaleate. The viny l acetate over cosurfactant molar ratio of limiting homogeneous system s varies in inverse sequence at the same monomer/water ratio. After ra dical polymerization of VAc in homogeneous samples transparent systems were obtained only when the polymer was solubilized in cosurfactant w ater mixtures.