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Polymerization Methods (polymerization + methods)
Selected AbstractsSynthesis of Composite Polystyrene/Silica Nanoparticles via Precipitation and Emulsion Polymerization MethodsMACROMOLECULAR REACTION ENGINEERING, Issue 5 2010Katerina Kotti Abstract Polystyrene/silica composite nanoparticles were synthesized via precipitation and emulsion polymerization methods, in the presence of a basic co-monomer (e.g., 4-VP and 1-VID), and a colloidal aqueous silica solution. The effects of key process parameters, that is, solvent type, monomer/co-monomer volume ratio and total monomers concentration for precipitation polymerization, and reaction temperature, pH value, initial silica-sol concentration and initial monomer/co-monomer molar ratio for emulsifier-free emulsion polymerization on the particle morphology, silica content, and particle size distribution of the composite nanoparticles were experimentally investigated. Stable, spherical, and uniform in size composite nanoparticles were synthesized by both techniques. The average particle diameter varied from 108 to 182,nm for the emulsifier-free emulsion polymerization and from 400 to 800,nm for the precipitation polymerization, while the silica content was as high as 38.3,wt.-% for the former method and up to 15.5,wt.-% for the later. The synthesized composite polymer/silica particles were then electrolytically co-deposited with zinc on steel plates to improve the corrosion resistance of the metal's surface. [source] Synthesis and characterization of PNIPAM/PS core/shell particlesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Li Zhang Abstract Crosslinked, monodisperse PNIPAM particles were synthesized by precipitation polymerization. The particle size was measured by dynamic light scattering (DLS), capillary hydrodynamic fractionation (CHDF), and transmission electron microscopy (TEM). Two different polymerization methods were used to prepare PNIPAM/PS core/shell particles, both above and below the volume phase transition temperature (VPPT) using either a semibatch or seeded semibatch polymerization process. In both processes, uniform "raspberry" structures were obtained in which polystyrene formed small domains on the surface of the PNIPAM particles. The resulting core and shell structure was confirmed by temperature-dependent particle size and density gradient experiments. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Effect of polymerization method on structure and properties of cationic polyacrylamideJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Yinghua Shen Abstract Acrylamide and 2-(methacryloyloxy)ethyltrimethylammonium chloride (AM/MADQUAT) copolymers were synthesized by solution and inverse microemulsion polymerization using (NH4)2S2O8/NaHSO3 as redox initiator at the same feed mole ratio, and their microstructure, such as sequence distribution and composition distribution, was calculated from monomer reactivity ratios of different polymerization methods. The results show that charge distribution is more uniform for copolymer prepared in inverse microemulsion than that in solution, and copolymer composition distribution is close to unity, and maintains approximately at the feed ratio. Furthermore, the influence of the two structures of cationic polyacrylamides on kaolinite floc size and effective floc density, reduction of Zeta potential and floc compressive yield stress had been investigated at pH 7. The results show that the kaolinite floc size and effective floc density are strongly dependent upon copolymer microstructure, with greater floc size and lower effective floc density being observed for copolymer prepared in inverse microemulsion than for that in solution. Copolymer microstructure has a marked effect on the Zeta potential, whose reduction in the magnitude was much greater in the presence of copolymer prepared in inverse microemulsion than that in solution. Greater compressive yield stress was achieved for the strong flocs produced by copolymer prepared in inverse microemulsion than for the weak flocs produced by that in solution. The difference in flocs compressive yield stress may be attributed to flocs structure. Therefore, in this article, a correlation between the cationic polyacrylamide structure and flocculation property for kaolinite suspension was established. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Synthesis of PMMA- b -PBA block copolymer in homogeneous and miniemulsion systems by DPE controlled radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2009Ying-Da Luo Abstract In this research, poly(methyl methacrylate)- b -poly(butyl acrylate) (PMMA- b -PBA) block copolymers were prepared by 1,1-diphenylethene (DPE) controlled radical polymerization in homogeneous and miniemulsion systems. First, monomer methyl methacrylate (MMA), initiator 2,2,-azobisisobutyronitrile (AIBN) and a control agent DPE were bulk polymerized to form the DPE-containing PMMA macroinitiator. Then the DPE-containing PMMA was heated in the presence of a second monomer BA, the block copolymer was synthesized successfully. The effects of solvent and polymerization methods (homogeneous polymerization or miniemulsion polymerization) on the reaction rate, controlled living character, molecular weight (Mn) and molecular weight distribution (PDI) of polymers throughout the polymerization were studied and discussed. The results showed that, increasing the amounts of solvent reduced the reaction rate and viscosity of the polymerization system. It allowed more activation,deactivation cycles to occur at a given conversion thus better controlled living character and narrower molecular weight distribution of polymers were demonstrated throughout the polymerization. Furthermore, the polymerization carried out in miniemulsion system exhibited higher reaction rate and better controlled living character than those in homogeneous system. It was attributed to the compartmentalization of growing radicals and the enhanced deactivation reaction of DPE controlled radical polymerization in miniemulsified droplets. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4435,4445, 2009 [source] Photoinitiated curing of mono- and bifunctional epoxides by combination of active chain end and activated monomer cationic polymerization methodsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2007Marco Sangermano Abstract Photoinitiated cationic polymerization of mono- and bifunctional epoxy monomers, namely cyclohexeneoxide (CHO), 4-epoxycyclohexylmethyl-3,,4,-epoxycyclohexanecarboxylate (EEC), respectively by using sulphonium salts in the presence of hydroxylbutyl vinyl ether (HBVE) was studied. The real-time FTIR spectroscopic, gel content determination, and thermal characterization studies revealed that both hydroxyl and vinyl ether functionalities of HBVE take part in the polymerization. During the polymerization, HBVE has the ability to react via both active chain end (ACE) and activated monomer mechanisms through its hydroxyl and vinyl ether functionalities, respectively. Thus, more efficient curing was observed with the addition of HBVE into EEC-containing formulations. It was also demonstrated that HBVE is effective in facilitating the photoinduced crosslinking of monofunctional epoxy monomer, CHO in the absence of a conventional crosslinker. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4914,4920, 2007 [source] Synthesis of Composite Polystyrene/Silica Nanoparticles via Precipitation and Emulsion Polymerization MethodsMACROMOLECULAR REACTION ENGINEERING, Issue 5 2010Katerina Kotti Abstract Polystyrene/silica composite nanoparticles were synthesized via precipitation and emulsion polymerization methods, in the presence of a basic co-monomer (e.g., 4-VP and 1-VID), and a colloidal aqueous silica solution. The effects of key process parameters, that is, solvent type, monomer/co-monomer volume ratio and total monomers concentration for precipitation polymerization, and reaction temperature, pH value, initial silica-sol concentration and initial monomer/co-monomer molar ratio for emulsifier-free emulsion polymerization on the particle morphology, silica content, and particle size distribution of the composite nanoparticles were experimentally investigated. Stable, spherical, and uniform in size composite nanoparticles were synthesized by both techniques. The average particle diameter varied from 108 to 182,nm for the emulsifier-free emulsion polymerization and from 400 to 800,nm for the precipitation polymerization, while the silica content was as high as 38.3,wt.-% for the former method and up to 15.5,wt.-% for the later. The synthesized composite polymer/silica particles were then electrolytically co-deposited with zinc on steel plates to improve the corrosion resistance of the metal's surface. [source] Synthesis of block copolymers by combination of ATRP and photoiniferter processesPOLYMER INTERNATIONAL, Issue 10 2008Yasemin Yuksel Durmaz Abstract BACKGROUND: Block copolymers of monomers polymerizing by different mechanisms can be prepared by the transformation approach. A wide range of combinations of different polymerization modes has been reported in the literature. In this work, the transformation approach was further extended to the preparation of block copolymers by combining atom transfer radical polymerization (ATRP) and photoiniferter processes. RESULTS: Photoactive morpholine-4-dithiocarbamate-terminated polystyrene (MDC-PS-MDC) was prepared by the reaction of dibrominated polystyrene, obtained by ATRP, with morpholine-4-dithiocarbamate sodium salt in dimethylformamide. The structure of MDC-PS-MDC was confirmed by 1H NMR and UV-visible spectral analysis. The ability of MDC-PS-MDC to act as a photoiniferter for the block copolymerization of methyl acrylate was examined. The polymerization shows a ,living' character at up to 25% conversion and produces well-defined polymers with molecular weights close to those predicted from theory and relatively narrow polydispersities (Mw/Mn , 1.40). CONCLUSION: It is demonstrated that the end groups of polymers obtained by ATRP can be converted into morpholino-4-dithiocarbamate groups which act as photoiniferters. In this way, the desired mechanistic transformation between two controlled free radical polymerization methods can be achieved. Copyright © 2008 Society of Chemical Industry [source] | ||||||||||