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We synthesize specially designed latex polymer systems by an in situ emulsion polymerization process that yields latex particles with both a high molecular weight polymer phase and a low molecular weight oligomer phase. The oligomer functions as a plastici/er by lowering the glass transition temperature ([T.sub.g]) of the polymer. A polymer system is prepared by blending soft latex and a hard latex where the hard mode consists of a hard, high molecular weight polymer and an oligomer, allowing for facile film formation at ambient conditions. Upon the soft and hard particles coming into contact during the film formation process, the oligomer preferentially diffuses from the hard polymer to the soft polymer, thus recovering the natural Ts of the hard polymer as described in a recent patent application. Oligomer diffusion allows a hard coalesced phase to be incorporated into a latex film without using a coalescing solvent, which would contribute to the volatile organic compound (VOC) content. A well-coalesced hard phase in a latex film contributes to a variety of desirable coatings properties, such as tack, print, block, and scrub resistance properties. Key words: oligomers, diffusion. Designed Diffusion™ Technology, plasticization. On a effectue la synthese de systemes de polymeres de latex concus specialement a cet effet en faisant appel a un processus de polymerisation en emulsion in situ qui conduit a la formation de particules de latex a la fois une phase de polymere de haul poids moleculaire el une phase d'oligomere de faible poids moleculaire. L'oligomere fonctionne comme plastifiant en reduisant la temperature de transition de verre ([T.sub.g]) du polymere. On prepare un systeme de polymere en procedant au melange d'un latex mou el d'un latex dur dans lequel le mode dur est forme d'une polymere dur de poids moleculaire eleve et d'un oligomere qui permet de former facilement un film dans les conditions ambiantes. Lorsque les particules molles et dures viennent en contact durant le processus de formation du film, l'oligomere diffuse d'une facon preferentielle du polymere dur vers le polymere mou et il retrouve la [T.sub.g] naturelle du polymere dur, tel que decrit dans une recente application pour un brevet. La diffusion de l'oligomere permet d'incorporer une phase dure ayant subi une coalescence d'etre incorporee dans un film de latex sans utiliser de solvant de coalescence qui contribuerait a la teneur en compose organique volatil (COV). Une phase dure qui a subi une bonne coalescence dans un film de latex contribue a une variete de proprietes desirables des revetements, telles que les proprietes resistance a la colle, a l'imprimerie, et au frottage. Mots-cles: oligomere, diffusion, technologie Designed Diffusion™, plasticisation. [Traduit par la Redaction], Introduction Demand of low and no volatile organic compound (VOC) binders in latex paints Water-borne latex coatings have been growing in popularity for decades as they offer performance, economic, and [...]

Abstract: Ultrasonically initiated miniemulsion polymerization of styrene in the presence of Fe3O4 nanoparticles was successfully employed to prepare polystyrene (PS)/Fe3O4 magnetic emulsion and nanocomposite. The effects of Fe3O4 nanoparticles on miniemulsion polymerization process, the structure, morphology and properties of PS/Fe3O4 nanocomposite were investigated. The increase in the amount of Fe3O4 nanoparticles drastically increases the polymerization rate due to that Fe3O4 nanoparticles increase the number of radicals and the cavitation bubbles. Polymerization kinetics of ultrasonically initiated miniemulsion polymerization is similar to that of conventional miniemulsion polymerization. PS/Fe3O4 magnetic emulsion consists of two types of particles: latex particles with Fe3O4 nanoparticles and latex particles with no encapsulated Fe3O4 nanoparticles. Fe3O4 nanoparticles lower the molecular weight of PS and broaden the molecular weight and particle size distribution. Thermal stability of PS/Fe3O4 nanocomposite increases with the increase in Fe3O4 content. PS/Fe3O4 emulsion and nanocomposite exhibit magnetic properties. PS/Fe3O4 magnetic particles can be separated from the magnetic emulsion by an external magnetic field and redispersed into the emulsion with agitation. [Copyright &y& Elsevier]