Gamma ray-induced seeded emulsion polymerization of methyl methacrylate and butyl acrylate was carried out in the presence of polymerizable polysiloxane seed latex, which was obtained by the ring-opening copolymerization of octamethyl cyclotetrasiloxane (D 4 ) and tetramethyl tetravinyl cyclotetrasiloxane(VD 4 ) catalyzed by dodecylbenzene sulfonic acid (DBSA). After the first seeded polymerization, 3-methacryloxylpropyltrimethoxylsilane (MPS) was added for the second seeded polymerization. The conversion-time curve showed that the first seeded polymerization rate was accelerated much by the polysiloxane seed latex. The final composite lattices also showed good storage stability, mechanical stability, and high electrolyte resistance ability. The morphology of the composite latex particles was found to be a quite uniform fine structure by transmission electron microscopy (TEM). The graft of polyacrylates onto polysiloxane and hydrolysis of MPS were confirmed by Fourier transform infrared (FT-IR) spectroscopy. The mechanical performance, water absorption ratio, surface properties, and transparency of the latex films were also investigated.
ABSTRACT:The photoinitiated copolymerization of vinyl pivalate (VPi) and vinyl acetate (VAc) was carried out in bulk. Varying monomer feed ratios of VPi/VAc (mol %/mol %) of 100/0, 90/10, 60/40, 50/50, and 30/70 were used. Polyvinyl alcohol (PVA) with s-diad contents ranging from 61.8% to 55.7% was obtained. The morphology and thermal properties of the different PVA samples were investigated. PVA prepared from PVPi homopolymer resulted in PVA with a well-aligned microfibrillar structure. With a decrease in the VPi content in the precursor polymer, the fibrous morphology was gradually lost, resulting in PVA with mixtures of fibrillar and spherical structures. When the PVPi content was 38.5 mol %, only spherical particles were observed.
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