Synthesis of multi-Layered polymer beads with UV scattering property

Abstract

Syntheses of three-novel types of multi-layered polymer beads, poly[(dimethyl aminoethyl methacrylate)-co-ST]/poly(methyl methacrylate)/polystyrene [P(DMAEMA-co-ST)/PMMA/PST] composite particles, with UV scatting property have been prepared successfully by the seeded emulsion polymerization using the following three steps. First, emulsion polymerization of P(DMAEMA-co-ST) seed latex was carried out using cetyltrimethyl ammonium chloride (CTAC) as a cationic stabilizer. The particle size of P(DMAEMA-co-ST) particles could be controlled by CTAC and 2,2'-azobis(2-amidinopropane)ฺ2HCl (V-50) concentrations. Second, methyl methacrylate (MMA) monomer was added into P(DMAEMA-co-ST) seed latex by dropwise method. It is found that the initiator types, V-50 or potassium persulfate (KPS), were the key factor for the morphology control of P(DMAEMA-co-ST)/PMMA composite particles. P(DMAEMA-co-ST)/PMMA composite particles were halfmoon-like morphology surrounded by the P(DMAEMA-co-ST)-rich phase when V-50 was used as an initiator, while a small P(DMAEMA-co-ST)-rich phase distributed inside of the PMMA-rich phase and inverted core-shell composite particles were produced when KPS was employed. Finally, P(DMAEMA-co-ST)/PMMA/PST composite particles were thus synthesized by seeded polymerization, using the above latex as the seed polymer and ST as the final-stage monomer. It was found that P(DMAEMA-co-ST)/PMMA seed particles were always surrounded by the PST-rich shell using V-50 as the initiator, while PS-rich phase partially engulfed by the P(DMAEMA-co-ST)-rich phase as a core covered by the PMMA-rich shell was obtained when the hydrophilic P(DMAEMA-co-ST)/PMMA composite particles having the lower molecular weight were used. The crosslinked P(DMAEMA-co-ST) seed particles of the first step did not affect the morphology of composite polymers. The refractive index depended on the morphology and particle size of composite polymers. The optimum morphology of composite polymers with a UV scattering property constituted a PMMA core containing small P(DMAEMA-co-ST) domains surrounded by the PST-rich shell. The reflection of which was 7.51% (n=1.755).