Polymerization of a Hydrophilic Monomer

The concentrated emulsion polymerization was also applied to an aqueous solution of acrylamide dispersed in decane. Compared to the conventional inverse emulsion polymerization [20], a much smaller amount of organic solvent is employed to produce polymer latexes. 

The Span 80 with an HLB (hydrophilic-lipophilic balance number) of 4,3, which is an oil soluble liquid, was used as surfactant. The effect of the continuous medium was investigated by employing 1,1,2,2-tetrachloroethane, toluene, or decane, which have various degrees of hydrophobicity. The amounts of the components used are listed in Table 3. At room temperature (20 °C), concen- 

The effect of the monomer concentration in the dispersed phase on the stability of the concentrated emulsions, with decane as the continuous medium, prepared at room temperature and heated at 60 °C for 5h, is presented in Fig. 24. The concentrated emulsion remains stable until a weight fraction of 0.2 is reached for larger values, the weight fraction which survives as concentrated emulsion decreases and becomes small for a weight fraction of 0.4. The loss of hydrophilicity caused by the increase in the amount of acrylamide accounts for the destabilization of the concentrated emulsion. 

The conversion as a function of time is plotted in Fig. 25. The figure also contains results obtained for identical conditions when solution polymerization was employed. Table 4 contains the molecular weights of the polyacrylamide 

It is important to emphasize that the concentrated emulsion polymerization of acrylamide in water leads to latexes of submicrometer size and employs a very small amount of organic solvent as compared to the conventional emulsion polymerization. 

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