D. Juhue et al., SURFACTANT EXUDATION IN THE PRESENCE OF A COALESCING AID IN LATEX FILMS STUDIED BY ATOMIC-FORCE MICROSCOPY, Journal of polymer science. Part B, Polymer physics, 33(7), 1995, pp. 1123-1133
We report atomic force microscopy images of surfactant (SDS) exudation
in PBMA latex films, in the presence and the absence of a coalescing
aid (TexanolTM, TPM). The exudates appear as hilly islets, and at time
s as mountains, at the film surface. Their size and number increase up
on annealing above the glass-transition temperature of the latex polym
er. TPM was found to be a strong promoter of surfactant exudation at t
he air-polymer interface. In the absence of TPM, annealing the films f
or several hours at 70 degrees C led to very little migration of surfa
ctant to the surface at most sites in the film. When the films with st
ructures of SDS on their surface were immersed in water, these structu
res disappeared. Pores, ranging in size from tens to hundreds of nm in
diameter, were clearly visible in the surface of the films. These fil
ms dry from the edges of the film inward, with a propagation front con
centrating the water-soluble species into a turbid, moist region in th
e center. At this site, the rate at which the surfactant comes to the
surface is enormously enhanced over that at other sites in the film. T
his is likely due to the high concentration of surfactant in this regi
on, transported there by the drying process. (C) 1995 John Wiley & Son
s, Inc.