MaterialsMonomer: Styrene99.9 %, FisherContinuous phase: WaterHPLC, AcroOrganicsNanoparticle: IPA-ST 10-15 nm silica nanoparticles dispersed in isopropanol30-31 wt%, Nissan ChemicalsInitiator: VA-086AzobisWater-solubleNonionic98 %, Wako Chemicals7ĨWhy Initiator VA-086?No success has been reported in surfactant-free emulsion polymerization of styreneSynthesis without silica nanoparticlesOpaque product (low conversion)No particle formation was observedThe initiator VA-086 has little effect on stabilizing an emulsion polymerization systemSilica nanoparticles are the only source of stabilizers when presentThe system do not contain surfactants nor auxiliary co-monomers200 nmĩSynthesisStyrene in water emulsion stabilized by silica nanoparticlesComposite particlesN2Add VA-086 solutionAt least 3 h70 oCWash*Characterization* Two centrifuging-redispersing cycles: centrifuge at 7000 rpm for 5 minutes at 23 oC and redisperse by manual shakingġ0Particle Morphology and Size Distribution(TEM, SEM, EDX, and DLS)VA-086: 0.06 gStyrene: 8 mLIPA-ST: 20 g(dried silica 6 g 2-propanol 14 g)Water: 52.5 gReaction time: 5 h200 nm200 nm2 µmġ1Silica Content(TGA)Composite particles200 nmHF treated particles†A. Mater.2007, 19, 2435-2445ĦObjectivesSynthesize core-shell structured polystyrene-silica composite particles by emulsion polymerization with a nonionic initiator, using silica nanoparticles as the sole stabilizing agentCharacterize particle size, morphology, and compositionTrack the change of particle size and surface coverage with reaction time at various initiator concentrations Core-Shell Composite ParticlesĤOne-Step Nanoparticle-Stabilized Emulsion Polymerizationnanoparticle-stabilizedemulsion polymerizationInorganic ParticlesPickering Emulsions(using solid nanoparticles as stabilizer)ĥelectrostaticattractionscationicinitiatorsnanoparticles( - )nonionicinitiatorsxSynthesis of Polystyrene-SilicaComposite ParticlesEmulsion polymerizationNo success has been reported using nanoparticles as the sole stabilizing agentDispersion polymerizationSolely stabilized by silica nanoparticlesCationic initiator AIBA – core-shell structure (up to 29 % silica)Nonionic initiator AIBN – poor coverage (up to 1.1 % silica)Really impossible?A. DaiChemical Engineering Arizona State UniversityAIChE Annual Meeting 2009ĢPolymer CompositesWide applicationsAutomotivesAircraftsElectronic devicesSports equipmentsPaintsFood packages…Advanced propertiesMechanicalThermalElectricalOptical…ģPolymer CompositesPolymerTraditional Composites+Inorganic ParticlesNewPolymer CompositesCore-Shell Composite ParticlesHow About?Traditional Polymer Composites vs. Synthesis of Polystyrene-Silica Composite Particles via One-Step Nanoparticle-Stabilized Emulsion Polymerization Huan Ma and Lenore L. Synthesis of Polystyrene-Silica Composite Particles via One-Step Nanoparticle-Stabilized Emulsion Polymerization