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Dispersion Copolymerization (dispersion + copolymerization)

Distribution by Scientific Domains
Polymers and Materials Science80%

Selected Abstracts

Dispersion copolymerization of methyl methacrylate and acrylic acid in polar media: effects of reaction parameters on the particle size and size distribution of the copolymer microspheres

POLYMER INTERNATIONAL, Issue 5 2003
Jin-Xia Huang
Abstract Micron-size functional crosslinked poly(methyl methacrylate) (PMMA) particles with narrow size distribution in the range of 1,5 µm were prepared by dispersion copolymerization in polar media with poly(N -vinylpyrrolidone)(PVP) as steric stabilizer, 2,2,-azobisisobutyronitrile(AIBN) as initiator and ethylene glycol dimethylacrylate (EGDMA) as crosslinking agent. The effects of functional comonomer acrylic acid (AA) concentration, contents in AIBN, EGDMA and PVP, media polarity as well as reaction temperature on the particle size and size distribution were investigated. Particle size initially increased, and then decreased with increasing AA concentration in the range of 0.7,3.5 mol l,1, having a maximum of 5.01 µm at the concentration of 2.1 mol l,1, while size distribution became broader. This was regarded as the result of different roles of PAA in the process. Particle size increased with decreasing media polarity and stabilizer concentration, and with increasing initiator concentration and reaction temperature. The resulting particle shapes were observed by transmission electron microscopy and the presence of carboxyl groups on the surface of the particles was confirmed by Fourier-transform infrared spectroscopy. Copyright © 2003 Society of Chemical Industry [source]

Stabilizer-free dispersion copolymerization of maleic anhydride and vinyl acetate.

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2005

Abstract A novel dispersion copolymerization of maleic anhydride (MAn) and vinyl acetate (VAc) without adding stabilizer is developed, which gives uniform copolymer microspheres with tunable sizes. Some principal factors affecting the microspheres, such as reaction time, monomer concentration and feed ratio, reaction media, and cosolvent, were investigated. It was found that the stabilizer-free dispersion copolymerization of MAn and VAc is a rapid process, and the particle size grows in accordance with the evolution of polymerization. The chemical composition of the copolymer microspheres was characterized by FT-IR and 13C NMR spectroscopies. Over a wide range of monomer concentrations, the microspheres can always be formed and stably dispersed, with uniform sizes ranging from 180 nm to 740 nm. The yield of copolymer microspheres reaches a maximum at 1:1 feed ratio of MAn to VAc, owing to the alternating copolymerization between the binary monomers by a known charge-transfer-complex mechanism. However, the diameter of microspheres drastically increases when MAn content is enhanced. Only some specific alkyl ester solvents, such as n -butyl acetate, isobutyl acetate, n -amyl acetate, are desirably fit for this unique stabilizer-free dispersion polymerization. Furthermore, we found that when some acetone is added as a cosolvent, the copolymer microspheres can still be formed, with much larger diameters. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3760,3770, 2005 [source]

Dispersion copolymerization of methyl methacrylate and acrylic acid in polar media: effects of reaction parameters on the particle size and size distribution of the copolymer microspheres

POLYMER INTERNATIONAL, Issue 5 2003
Jin-Xia Huang
Abstract Micron-size functional crosslinked poly(methyl methacrylate) (PMMA) particles with narrow size distribution in the range of 1,5 µm were prepared by dispersion copolymerization in polar media with poly(N -vinylpyrrolidone)(PVP) as steric stabilizer, 2,2,-azobisisobutyronitrile(AIBN) as initiator and ethylene glycol dimethylacrylate (EGDMA) as crosslinking agent. The effects of functional comonomer acrylic acid (AA) concentration, contents in AIBN, EGDMA and PVP, media polarity as well as reaction temperature on the particle size and size distribution were investigated. Particle size initially increased, and then decreased with increasing AA concentration in the range of 0.7,3.5 mol l,1, having a maximum of 5.01 µm at the concentration of 2.1 mol l,1, while size distribution became broader. This was regarded as the result of different roles of PAA in the process. Particle size increased with decreasing media polarity and stabilizer concentration, and with increasing initiator concentration and reaction temperature. The resulting particle shapes were observed by transmission electron microscopy and the presence of carboxyl groups on the surface of the particles was confirmed by Fourier-transform infrared spectroscopy. Copyright © 2003 Society of Chemical Industry [source]

Preparation of Core-shell Microspheres by ATRP Synthesized Macromonomer

CHINESE JOURNAL OF CHEMISTRY, Issue 10 2008
Hong CHU
Abstract Poly(tert -butyl methacrylate) macrointermediates (PtBMA-Br) with an end of bromine atom were synthesized by atom transfer radical polymerization using ethylbromopropionate as an initiator in bulk in the presence of N,N,N,,N,,,N,, -pentamethyl diethylenetriamine (PMDETA) as a single ligand. A new macromonomer (MAA- PtBMA) was successfully prepared via end-group nucleophilic substitution with methacrylic acid to attain a high efficiency of C=C incorporation. The molecular weights of MAA-PtBMA macromonomers were controllable from 5400 to 11000 g/mol, and the molecular weight distribution was narrow (,1.20). Then, the PtBMA graft polystyrene (PtBMA-g-PSt) microspheres were prepared by dispersion copolymerization of MAA-PtBMA macromonomers with styrene using 2,2,-azobisisobutyronitrile as a free radical initiator in ethanol. The resulting PtBMA-g-PSt microspheres were regulated in diameter on a micron scale. [source]