SURFACE AND INTERFACIAL FTIR SPECTROSCOPIC STUDIES OF LATEXES .4. THE EFFECT OF SURFACTANT STRUCTURE ON THE COPOLYMER SURFACTANT INTERACTIONS

The interactions between sodium dodecylbenzene sulfonate (SDBS) and the components of an ethyl acrylate/methacrylic acid (EA/MAA) copolymer latex were examined and the influences of using D2O as the synthetic suspension medium were investigated. Whereas it is found that D2O has no detectable influence on the fully coalesced latex films, the film coalescence conditions are shown to significantly affect the nature of surfactant interactions within the film matrix. When films are prepared and stored under controllable low atmospheric water-vapor concentrations, hydrogen-bonding interactions between the surfactant SO3-Na+ groups and the copolymer acid functionality dominate. However, coalescence and storage of the films under higher relative humidity conditions results in a displacement of these interactions in favor of the hydrated form of the surfactant. It is also shown that the presence of an aromatic ring adjacent to the surfactant sulfonate group exerts an influence on the nature of the SO3-...HOOC interactions within the copolymer matrix. Relative to sodium dioctyl sulfosuccinate (SDOSS), the aromatic group near hydrophilic end of SDBS increases the strength of the S-O bond in the presence of acid interactions.