SURFACE CHARACTERIZATION OF LATEXES WITH DIFFERENT INTERFACIAL PROPERTIES

In this paper we have studied the effect of copolymerization of a non- ionic but hydrophilic monomer on the interfacial properties of the lat ex surface. Hydrophilic polymer colloids were prepared by the emulsifi er-free emulsion copolymerization of styrene and 2-hydroxyethyl methac rylate (HEMA) with potassium persulfate as initiator. The copolymer co mpositions were evaluated by H-1 nuclear magnetic resonance and compar ed with the initial concentration of each monomer. Results show very g ood agreement which is an indication of the absence of secondary nucle ation. Also, the presence of the carbonyl group (i.e. a weak acid grou p) was detected by Fourier transform-infrared and C-13 nuclear magneti c resonance analysis, together with conductometric and potentiometric titration experiments. In all cases, a conventional hydrophobic polyst yrene latex was used as a reference. The hydrophobic character of the latexes was estimated by using contact angle and viscosity measurement s, and adsorption of a non-ionic surfactant. These three methods are c ompared. As expected, the results showed that as the amount of hydroph ilic monomer in the synthesis increases, so does the hydrophilic chara cter of the latex surface.