Determination of surface car☐yl groups in styrene/itaconic acid copolymer latexes

TLDR: In this paper, the modes of distribution of acid monomer in two styrene/itaconic acid copolymer latexes prepared with varying emulsifier types were estimated by conductometric titration.

Abstract: The modes of distribution of acid monomer in two styrene/itaconic acid copolymer latexes prepared with varying emulsifier types were estimated by conductometric titration. The concentrations of acid bound at the surface of the latex particles (“surface bound”) and “free” acid in the water phase can be determined in a single conductometric titration. The concentration of acid “buried” within the latex particles was obtained from the differences between the charge of acid during polymerization and the conductometric titration results. It was found that a larger particle size latex had much lower concentration of “total bound” and “surface bound” acids and higher “free” acid concentration than a smaller particle size latex. Although conductometric titration is suitable for determining the loci of car☐yl groups in polystyrene latexes, it may not apply to all car☐ylated latexes. Analysis of the isolated water phase of styrene/itaconic acid copolymer latexes by G.P.C. indicated the presence of oligomers containing weak acid groups with MW ranging between 2500 and 5000. These oligomers are generated “in situ” during latex polymerization and may become important in conferring adequate latex stability during preparation of car☐ylated latexes of low emulsifier content.