Nanostructured latexes made by a sequential multistage emulsion polymerization

A series of linear and lightly crosslinked nanostructured latices was prepared by a sequential multistage semicontinuous emulsion polymerization process alternating styrene (S) and n-butyl acrylate (BA) monomer feeds five times, that is ten stages, and vice versa, along with several control latices. Transmission electron micrographs of the RuO4-stained cross sections of nanostructured and copolymer latex particles and films showed that their particle morphologies were not very different from each other, but the nanostructured latex particles were transformed into a nanocomposite film containing both polystyrene (PS) and poly(n-butyl acrylate) (PBA) nanodomains interconnected by their diffuse polymer mixtures (i.e. interlayers). The thermal mechanical behaviors of the nanostructured latex films showed broad but single T(g)s slightly higher than those of their counterpart copolymer films. These single T(g)s indicated that their major component phases were the diffuse interlayers and that they behaved like pseudopolymer alloys. The minimum film formation temperatures of nanostructured latices capped with PBA and PS, respectively, were 15 degrees C lower than and equal to those of their counterpart copolymer latices, but their T(g)s were about 10 degrees C higher. Consequently, nanostructured latices enabled us to combine good film formation with high strengths for adhesives and coatings applications. (c) 2006 Wiley Periodicals, Inc.