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1.
Poly(methyl methacrylate) (PMMA) particles were produced by dispersion polymerization of methyl methacrylate in the presence of mercaptopropyl terminated poly(dimethylsiloxane) (MP-PDMS) in supercritical carbon dioxide at about 30 MPa for 24 h at 65 °C. The particle diameter could be controlled in a size range of submicron to micron by varying MP-PDMS concentration. The MP-PDMS worked as not only a chain transfer agent but also a colloidal stabilizer, which was named tran
stab.Part CCLI of the series Studies on suspension and emulsion 相似文献
2.
Eri Yoshida 《Colloid and polymer science》2008,286(3):351-355
The synthesis of polystyrene microspheres was achieved by the dispersion polymerization of styrene in supercritical carbon
dioxide using azobisisobutylonitrile (AIBN) and a poly(dimethylsiloxane) (PDMS)-based macroazoinitiator, VPS-1001. VPS-1001
contained seven to nine molecules of the azo groups and the PDMS blocks with a molecular weight of 10,000 per molecule. The
polymerization in the presence of both VPS-1001 and AIBN produced polystyrene microspheres with a diameter below 4 μm in over
85% yields, whereas the polymerization with VPS-1001 in the absence of AIBN provided a nonspecific polystyrene in only 20%
yield. The particle size decreased as a result of increasing the concentration of VPS-1001. It was confirmed that the polystyrene
particles were stabilized by the PDMS-block-polystyrene formed through the polymerization initiated by VPS-1001 because the polymerization using a PDMS homopolymer provided
nonspecific polystyrene as a precipitate during the polymerization. 相似文献
3.
Eri Yoshida 《Colloid and polymer science》2008,286(12):1435-1442
The novel synthesis of polyhedral particles was attained by the dispersion polymerization of styrene in supercritical carbon
dioxide using a polydimethylsiloxane-based macroazoinitiator as a precursor of the surfactant. The macroazoinitiator, VPS-1001,
composed of poly(dimethylsiloxane) and 6-8 molecules of the azo groups served as a precursor of the surfactant for the dispersion
polymerization by azobisisobutylonitrile as an initiator to produce 0.8-4 μm polyhedral particles. The size of the particles
decreased as a result of increasing the VPS-1001 concentration. Too high a concentration of VPS-1001 caused coagulation of
the particles. A decrease in the temperature increased the particle size and size distribution, while a decrease in the pressure
produced particles with nonspecific shapes. An increase in the stirring rotation speed tended to increase the size and size
distribution. However, too high a speed of rotation also caused coagulation of the particles. 相似文献
4.
This paper describes the development and application of power compensation calorimetry equipment to monitor the dispersion polymerisation of methyl methacrylate in supercritical carbon dioxide. We have studied the polymerisation of methyl methacrylate using a macromonomer (poly(dimethylsiloxane) monomethacrylate) as stabiliser and initiator azoisobutylnitrile. The calorimetric data allow monitoring of the polymerisation process. Through monitoring the changes in reaction exotherm and system pressure during the polymerisation one can clearly observe the point at which the polymerisation starts and effectively ceases. The effect of initiator concentration and stabiliser on the reaction was studied and the enthalpy of polymerisation obtained from the apparatus was found to correlate with previously reported data. 相似文献
5.
Masayoshi Okubo Yukiya Kitayama Tomoya Taniyama Xiang Liu Jianzheng Zhang Hao Shi 《Journal of polymer science. Part A, Polymer chemistry》2019,57(5):613-620
Reversible chain transfer catalyzed polymerization (RTCP) in dispersion polymerization system (dispersion RTCP) of methyl methacrylate (MMA) was performed with N‐iodosuccimide (NIS) as a nitrogen catalyst in supercritical carbon dioxide (scCO2). The solubility of NIS in scCO2 can be controlled by tuning the pressure, and this led to promote NIS partitioning into polymerizing particles. As a result, the molecular weight distribution control was successfully improved by decreasing the NIS solubility in the medium by tuning the scCO2 at a low pressure of 20 MPa. On the other hand, at the same NIS concentration, a solution RTCP of MMA in toluene as a homogeneous polymerization system did not proceed with a controlled/living manner. The importance of NIS partitioning into the polymerizing particles was also confirmed in hexane as well as scCO2 medium. From these results, it was clarified that the NIS catalyst partitioning into the polymerizing particles as main polymerization loci is a key factor to control the molecular weight distribution in the dispersion RTCP of MMA in scCO2. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 613–620 相似文献
6.
Dispersion polymerizations of methyl methacrylate (MMA) were conducted with various types of organic peroxides as radical initiator in the presence of trimethylsiloxy terminated poly(dimethylsiloxane) in supercritical carbon dioxide. Micron-sized, relatively “monodisperse” poly(MMA) particles were prepared by using benzoyl peroxide.Part CCLII of the series “Studies on Suspension and Emulsion” 相似文献
7.
In this study, the poly(methyl methacrylate-co-2,2,3,4,4,4-hexafluorobutyl methacrylate) [P(MMA-co-HFBMA)] as a fluoric copolymer was prepared using dispersion polymerization in supercritical carbon dioxide. The characterization for the prepared P(MMA-co-HFBMA) was investigated with varied ratios of MMA vs HFBMA (30:1, 25:1, 22:1 and 20:1), 2,2′-azobisisobutyronitrile (AIBN) amounts (1.0, 2.0, 3.0, and 4.0) wt% and the weight average molar mass (Mw).Experimental cloud-point data at temperatures to 454 K and pressures up to 184 MPa are reported for binary and ternary mixtures of P(MMA-co-HFBMA) in supercritical CH2F2, CHF3 and CHClF2. Experiments are performed in order to determine phase behaviour of binary system for the P(MMA-co-HFBMA) (mole ratio: 25:1, AIBN: (1.0, 2.0, 3.0 and 4.0) wt%) + supercritical solvents (CH2F2, CHF3 and CHClF2) mixtures at temperature range from (333 to 454) K and pressure up to 184 MPa. It appears that the {P(MMA-co-HFBMA) + CH2F2} mixtures show the upper critical solution temperature (UCST) type behaviour with negative slope, while the {P(MMA-co-HFBMA) + CHF3} and {P(MMA-co-HFBMA) + CHClF2} mixtures show lower critical solution temperature (LCST) type curve with positive slope. Cloud-point curves for the P(MMA-co-HFBMA) [mole ratio: 30:1 (Mw = 186,000 g · mol−1), 25:1 (Mw = 176,000 g · mol−1), 22:1 (Mw = 158,000 g · mol−1) and 20:1 (Mw = 126,000 g · mol−1); AIBN: 1.0 wt%) + supercritical (CH2F2, CHF3 and CHClF2) mixtures show a negative slope for the {P(MMA-co-HFBMA) + CH2F2}, and a positive slope for the {P(MMA-co-HFBMA) + CHF3} and {P(MMA-co-HFBMA) + CHClF2} mixtures at temperatures to 454 K and pressure up to 184 MPa. Also, the impact of MMA on phase behaviour for the {P(MMA-co-HFBMA) (mole ratio: 25:1; AIBN: (1.0 and 2.0) wt%) + CH2F2} mixtures are measured in changes of the (pressure + temperature) slope from UCST behaviour to LCST behaviour, and with MMA co-solvent concentrations of (0.0 to 40.1) wt%. 相似文献
8.
Cross-linked poly(methyl methacrylate) particles were prepared via dispersion polymerization in supercritical carbon dioxide
(scCO2) using poly(heptadecafluorodecyl methacrylate) (PHDFDMA) and 2,2′-azobisisobutyronitrile as the dispersant and the initiator,
respectively. The following chemicals were used as cross-linking agents: ethylene glycol dimethacrylate (EGDMA), 1,4-buthanediol
di(meth)acrylate (1,4-BD(M)A), and trimethylolpropane trimethacrylate. PHDFDMA was synthesized by solution polymerization
in scCO2. We investigated the effect of the chemical structure, concentration of the cross-linking agents, reaction pressure, and
CO2 density on the morphology, the polydispersity, and the cross-linking density of polymer particles. The resulting polymer
particle was characterized by field emission SEM, differential scanning calorimetry, and thermal gravimetric analysis. The
cross-linked PMMA particles is more agglomerate as the cross-linking agent concentration increased and as pressure decreased
at constant temperature. Glass-transition temperature (T
g) of the resulting polymer increased as the cross-linking agent increased with temperature and pressure increasing at the
same CO2 density. Decomposition temperature is slightly increased as 1,4-BDA concentration increased. From these results, we can confirm
that the thermal stability of the polymer increased as the cross-linking agent and EGDMA is the best cross-linking agent in
term of the thermal stability. 相似文献
9.
Morphology of micron-sized monodispersed poly(butyl methacrylate)/polystyrene composite particles produced by seeded dispersion polymerization 总被引:1,自引:0,他引:1
In order to develop the seeded dispersion polymerization technique for the production of micron-sized monodispersed core/shell
composite polymer particles the effect of polymerization temperature on the core/shell morphology was examined. Micron-sized
monodispersed composite particles were produced by seeded dispersion polymerizations of styrene with about 1.4-μm-sized monodispersed
poly(n-butyl methacrylate) (Pn-BMA) and poly(i-butyl methacrylate) (Pi-BMA) particles in a methanol/water (4/1, w/w) medium in the temperature range from 20 to 90 °C. The composite particles,
PBMA/polystyrene (PS) (2/1, w/w), consisting of a PBMA core and a PS shell were produced with 2,2′-azobis(4-methoxy-2,4-dimethyl
valeronitrile) initiator at 30 °C for Pn-BMA seed and with 2,2′-azobis(isobutyronitrile) initiator at 60 °C for Pi-BMA seed. The polymerization temperatures were a little above the glass-transition temperatures (T
g) of both Pn-BMA (20 °C) and Pi-BMA (40 °C). On the other hand, when the seeded dispersion polymerizations were carried out at much higher temperatures than
the T
g of the seed polymers, composite particles having a polymeric oil-in-oil structure were produced.
Received: 14 October 1998 Accepted in revised form: 2 June 1999 相似文献
10.
John M. Stubbs 《Fluid Phase Equilibria》2011,305(1):76-82
The partitioning of ethylbenzene between poly(ethylene glycol) (PEG) and supercritical carbon dioxide was studied at 308.15, 328.15 and 348.15 K and 10, 15.5 and 20 MPa with PEG-400, 600 and 900 using Monte Carlo molecular simulation. The effect of a cosolvent was also studied with either 5% ethane or 5% n-octane added. Ethylbenzene favored the supercritical phase most when the density was highest, and while ethane had little effect, the addition of n-octane increased the amount of solute dissolved in carbon dioxide. Increasing polymer molecular weight led to more solute in the PEG-rich phase. This coincides with a higher amount of dissolved carbon dioxide that preferentially solvates ethylbenzene. 相似文献
11.
To make clear the reason of unsuitability of poly(vinyl alcohol) (PVA) protective colloid for the emulsion polymerization
of conjugated monomers, a model experiment of emulsion polymerization of methyl methacrylate (MMA) was carried out with ammonium
persulfate (APS) or azobis(isobutyronitrile) (AIBN) initiators, where a small amount of MMA (1/100th of the concentration
compared with ordinary emulsion polymerization) was employed. This corresponds to the initial stage of the emulsion polymerization.
Grafting of MMA onto PVA took place remarkably irrespective of the kind of the initiators. Formation of homo-poly(MMA) was
observed to a small extent. The formation of new emulsion particles smaller than 100 nm continued to increase to almost the
end of the polymerization. PVA molecules in the grafted polymer are supposed to act as stabilizers of newly formed particles.
From kinetic treatment using the experimental data, the important issues were derived as follows. Firstly, the sulfate anion
radical from APS is much more reactive than the isobutyronitrile radical from AIBN in terms of hydrogen abstraction from PVA.
Secondly, high grafting ability of the latter initiator system, notwithstanding the much lower reactivity in the hydrogen
abstraction compared with the APS system, is attributed to the relative reactivity of the primary radicals, i.e., hydrogen
abstraction reaction from PVA to initiation reaction with MMA. The much slower rate of addition of the isobutyronitrile radical
to the monomer compared with that of hydrogen abstraction from PVA facilitates the grafting, although the rate constant of
hydrogen abstraction is far smaller than that with the sulfate anion radical by 10−4 times.
Received: 26 April 2001 Accepted: 6 September 2001 相似文献
12.
Kyung Min Do Haldorai Yuvaraj Min Hee Woo Hyun Gyu Kim Euh Duck Jeong Keith P. Johnston Kwon Taek Lim 《Colloid and polymer science》2008,286(11):1343-1348
A novel synthetic route to prepare polystyrene/SiO2 composite microparticles in supercritical carbon dioxide (scCO2) is presented. Silica particles with the size of 130 nm which were surface-modified with 3-(trimethoxysilyl) propyl methacrylate
were used as seeds in the dispersion polymerization of styrene in the presence of a polymeric stabilizer, poly(1,1-dihydroheptafluorobutyl
methacrylate-co-diisopropylaminoethyl methacrylate) to produce dry composite particles. The transmission electron microscopy analysis revealed
that the composite microspheres contained several silica particles. 相似文献
13.
Poly(ethylene oxide) macromonomers carrying methoxy group on the one (α-) end and methacryloyloxyhexyl or methacryloyloxydecyl
group on the other (ω-) end were prepared, homopolymerized in water, and dispersion-copolymer-ized with styrene or methyl
methacrylate in a methanol–water mixture. They were found to polymerize more rapidly and to produce stable polystyrene dispersions
more effectively, as compared to the corresponding macromonomers carrying either α-methoxy and or α-dodecyloxy and ω-methacryloyloxy
end groups. Thus, the amphiphilic constitution of the macromonomers such that favors the polymerizing methacrylate end groups
to locally concentrate into the micelle core or to the particle surface while the poly(ethylene oxide) chains extending to
the medium appears to be most important in enhancing their polymerizability and effectiveness as reactive steric stabilizers.
On the other hand, stable poly(methyl methacry-late) particles with a number of craters or pleats on the surface were produced
with a PEO macromono-mer with α-methoxy and ω-methacryl-oyloxy end groups.
Received: 4 September 1996 Accepted: 18 October 1996 相似文献
14.
Hiroshi Shiho Joseph M. DeSimone 《Journal of polymer science. Part A, Polymer chemistry》2000,38(20):3783-3790
Herein we report a successful dispersion polymerization of 2‐hydroxyethyl methacrylate (HEMA) in a carbon dioxide continuous phase with a block copolymer consisting of polystyrene and poly(1,1‐dihydroperfluorooctyl acrylate) as a stabilizer. Poly(2‐hydroxyethyl methacrylate) was effectively emulsified in carbon dioxide with the amphiphilic diblock copolymer surfactant, and the successful stabilization of the polymerization simultaneously gave spherical particles in the submicrometer range with relatively narrow particle size distributions. The initial concentrations of HEMA and the stabilizer and the pressure had substantial effects on the size of the colloidal particles. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3783–3790, 2000 相似文献
15.
Soyoung Kwon Kyoungwon Lee Hwayong Kim Youn-Woo Lee Won Bae 《Colloid and polymer science》2008,286(10):1181-1191
The free radical copolymerization of N-vinyl-2-pyrrolidone and 2-methylene-1,3-dioxepane was carried out in supercritical carbon dioxide (scCO2) using three kinds of dispersants and 2,2′-azobisisobutyronitrile as the initiator. Polymerization was performed with fluorinated
polymeric dispersants synthesized in scCO2 using the solution polymerization method and commercially available siloxane-based surfactant. Spherical biocompatible and
biodegradable polymeric particles were prepared within the sub-micron size range. The effect of various ratios of the comonomer,
reaction temperature, and concentration of initiator, in addition to the types and concentrations of the dispersants, on the
particle size and morphology was investigated. The particle size and particle size distribution of copolymer particles were
controlled using the above mentioned experimental parameters. Glass transition temperatures of copolymers were varied according
to the comonomer ratios used. 相似文献
16.
Van Hoa Nguyen Yuvaraj Haldorai Seok Kyun Noh Jae-Jin Shim 《European Polymer Journal》2010,46(11):2190-2198
We report here a successful free-radical dispersion polymerization of vinyl pivalate (VPi) in an ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][TFSI]) using poly(vinyl pyrrolidone) (PVP) as a stabilizer. Morphological analysis by FE-SEM revealed that poly(vinyl pivalate) (PVPi) obtained from dispersion polymerizations were in the form of spherical particles. Micron-sized, PVPi particles with a number-average molecular weight (Mn) of 166,400 g/mol could be obtained using 5% stabilizer (w/w to monomer) at 65 °C for 20 h. The effects of varying concentration of stabilizer, initiator and monomer upon polymer yield, molecular weight, and morphology of PVPi were also investigated. Analogous polymerizations in dimethyl sulfoxide (DMSO) and bulk served as references. In addition, the preparation of poly(vinyl alcohol) (PVA) by saponification of the resultant PVPi was described. 相似文献
17.
Shin Ichi Kuroda 《中国化学快报》2011,22(9):1127-1129
Submicron-sized peanut-shaped poly(methyl methacrylate)/polystyrene(PMMA/PS) particles were successfully synthesized by seeded soap-free emulsion polymerization of styrene on the spherical crosslinked PMMA seed particles.The obtained peanut-shaped particles showed a novel internal morphology:PS phase formed one domain which linked to the other domain having PMMA core encased by PS shell. 相似文献
18.
Wan Jiang Wuli Yang Xianbiao Zeng Shoukuan Fu 《Journal of polymer science. Part A, Polymer chemistry》2004,42(3):733-741
Nanoscale poly(methyl methacrylate) (PMMA) particles were prepared by modified microemulsion polymerization. Different from particles made by traditional microemulsion polymerization, the particles prepared by modified microemulsion polymerization were multichain systems. PMMA samples, whether prepared by the traditional procedure or the modified procedure, had glass-transition temperatures (Tg's) greater than 120 °C and were rich in syndiotactic content (55–61% rr). After the samples were dissolved in CHCl3, there were decreases in the Tg values for the polymers prepared by the traditional procedure and those prepared by the modified process. However, a more evident Tg decrease was observed in the former than in the latter; still, for both, Tg was greater than 120 °C. Polarizing optical microscopy and wide-angle X-ray diffraction indicated that some ordered regions formed in the particles prepared by modified microemulsion polymerization. The addition of a chain-transfer agent resulted in a decrease in both the syndiotacticity and Tg through decreasing polymer molecular weight. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 733–741, 2004 相似文献
19.
We report the successful precipitation polymerization of 2‐hydroxyethyl methacrylate (HEMA) in supercritical carbon dioxide (scCO2) at pressures ranging from 15 to 27 MPa utilizing 2, 2′‐azobisisobutyronitrile (AIBN) as a free radical initiator. The effects of the reaction pressure, initiator concentration, monomer concentration, reaction temperature, and reaction time were investigated. Analyses by scanning electron microscopy (SEM) indicated that in all reaction conditions, polymerization in the absence of stabilizer led to the formation of large aggregates of partially coalesced particles, with diameters of approximate 1–10 µm. Analyses by gel permeation chromatography (GPC) indicated that for the reaction pressure, initiator concentration, monomer concentration, reaction temperature, and reaction time studied there are appreciable effect on product molecular weight. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
20.
Lunhan Ding Susan V. Olesik 《Journal of polymer science. Part A, Polymer chemistry》2003,41(23):3804-3815
The dispersion polymerization of styrene in carbon dioxide with a series of copolymers of poly(propylene glycol) methacrylate (PPGMA) and 2‐(perfluorooctyl)ethyl methacrylate (FOEMA) as the polymerization dispersants was examined. It was demonstrated that PPGMA and FOEMA copolymers and polymers containing 52–100% FOEMA could be used as effective dispersants for the polymerization, and the composition of the copolymeric dispersant had a dramatic effect on both the polymerization yield and the morphology of the resulting polystyrene. The effects of the concentrations of the copolymeric dispersants, the concentrations of the monomer, and the reaction pressure were also investigated. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3804–3815, 2003 相似文献