SYNTHESIS OF POLYSTYRENE HYBRID NANOPARTICLES WITH PREFORMED POLYMERS OF VARIED COMPATIBILITY BY MINIEMULSION POLYMERIZATION

RONCO, LUDMILA I.; MINARI, ROQUE J.; VEGA, JORGE R.; GUGLIOTTA, LUIS M.

Cancún

Conferencia; Polymer Reaction Engineering Conference; 2012

ECI

Waterborne hybrid latexes are an opportunity for developing new products based on the synergy effects of highly compatible compounds. Miniemulsion (ME) polymerizations allow the incorporation of hydrophobic components (like butadiene based-rubbers) into polystyrene (PS) nanoparticles, in order to produce nanostructured particles for their use as high-impact resistance materials. Unfortunately, PS and polybutadiene (PB) are incompatible and tend to produce phase separation. The compatibilization of phases may be affected by the ME formulation, the polymerization conditions, and the molecular structure and content of the preformed polymer. In this work, ME polymerizations were used to synthesize PS hybrid nanoparticles which incorporate preformed polymers with varied degree of compatibility and molecular weight (M). To this effect, the following preformed polymers were used: PB as an incompatible polymer, styrene-butadiene random copolymer (SBR) as a partially compatible polymer, and PS as a compatible polymer. Potassium persulfate (KPS) or tert-butyl hydroperoxide/ascorbic acid (TBHP/ AA) were the employed initiator systems. All ME were stable, as determined after 4-hours scanning with a Turbiscan. It was observed that for a reduced content of preformed polymers presenting low M, the droplets diameter (dd) was decreased, thus improving their nucleation and the compatibility of the hybrid particles. Droplets nucleation was also improved by employing TBHP/AA instead of KPS. When decreasing the compatibility of the system (e.g., by employing PB as preformed polymer) the droplets nucleation was drastically reduced, and a considerable amount of coagulum (enriched in PB) was obtained. Finally, secondary particle formation was easily identified through TEM images of latexes with low droplets nucleation efficiency.