Hollow core-shell particles via NR latex seeded emulsion polymerization. (2nd September 2016) - Wichaita, Waraporn
Abstract: Natural rubber (NR)-based hollow latex (HL) particles have been prepared by seeded emulsion polymerization of methyl methacrylate/divinyl benzene/acrylic acid (MMA/DVB/AA) monomers on NR seed. By using tert -butyl hydroperoxide/tetraethylene pentamine ( t -BuHP/TEPA) as a redox initiator, the locus of polymerization was localized at the surface of the NR particle. After swelling with monomers, DVB in NR particle gradually moved outward to compensate the co-polymerization. Phase separation between the NR seed and the polymeric shell occurred and a void was subsequently formed at a MMA/DVB molar ratio of 2.7/1. The void cavity was enlarged when the monomer to seed (M/S) weight ratio was increased to 4/1. Without the necessity of any residual core removal, polydisperse NR-based hollow nanocomposites (298 ± 58 nm) possessing NR-P(MMA/DVB/AA) double-layered shell and a single void (155 ± 37 nm) were obtained. SEM images revealed an increase in surface roughness of the HL particle with increasing M/S weight ratios. The large specific surface area of these NR-based hollow nanocomposites (114.6 m 2 /g) with a 3.5 nm pore diameter indicates that the polymeric shell is mesoporous. The presence of carboxyl groups, as indicated by negative zeta potentials, can further facilitate surface functionalization. The large void cavity of these NR-based HL particles makes them particularly suited as delivery vehicle systems. Graphical abstract: Highlights: One-pot synthesis of HL particles using NR as seed is presented for the first time. Hollow core-shell structure is formed without core fabrication and removal steps. Polymerization locus at the surface of NR seed is induced by the redox initiator. Void formation is controlled by MMA/DVB content and monomers/seed ratios. Double shell HL would have good mechanical properties for further uses as capsules.