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1.
Micron-sized mono-dispersed polystyrene (PS)/poly(n-butyl methacrylate) (PBMA) composite particles (PS/PBMA=2/1 by weight) having a heterogeneous structure in which many fine
PBMA domains dispersed in a PS matrix near the particle surface were produced by seeded polymerization of n-butyl methacrylate (BMA) of which almost all had been absorbed by 1.8 μm-sized monodispersed PS seed particles utilizing
the dynamic swelling method. The morphology was varied by changing the PS/BMA ratio and polymerization temperature. It was
concluded that the swelling state of 2 μm-sized BMA-swollen PS particles in the seeded polymerization process is one of the
important factors to control the morphology of the composite particles.
Received: 27 November 1996 Accepted: 21 March 1997 相似文献
2.
M. Okubo E. Ise T. Yamashita 《Journal of polymer science. Part A, Polymer chemistry》1998,36(14):2513-2519
For the purpose of extending the size range of polymer seed particles used in “dynamic swelling method” (DSM), first it was verified theoretically that the submicron-sized polymer particles produced by emulsion polymerization can also absorb a large amount of monomer by DSM in both equilibrium and kinetic control states. Next, on the basis of the theoretical results, experimentally about 2.6 μm-sized styrene-swollen polystyrene (PS) particles were prepared utilizing DSM in the presence of 0.64 μm-sized monodispersed PS seed particles produced by emulsifier-free emulsion polymerization. Moreover, 2.5 μm-sized monodispersed PS particles were produced by the addition of cupric chloride as a water-soluble inhibitor to depress the by-production of submicron-sized PS particles in the seeded polymerization at 30°C with 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile) initiator. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2513–2519, 1998 相似文献
3.
Micron-sized, monodispersed highly styrene-“adsorbed” particles having snow-man shape were prepared by the dynamic swelling
method (DSM) with tightly cross-linked polymer seed particles as follows. First, 3.8 μm-sized monodispersed polystyrene (PS)/
poly(divinylbenzene) (PDVB) (PS/PDVB = 1/10 wt. ratio) composite particles produced by seeded polymerization utilizing DSM
were dispersed in an ethanol/water (6/4, w/w) solution dissolving styrene monomer, and poly(vinyl alcohol) as a stabilizer.
Second, water was subsequently added to the dispersion with a micro-feeder at a rate of 2.88 ml/h at room temperature. The
cross-linked seed particles adsorbed a large amount of styrene onto the surfaces and resulted in mono-dispersed highly styrene-“adsorbed”
snow-man shape particles having about 10 μm in diameter.
Received: 16 April 1998 Accepted: 9 June 1998 相似文献
4.
Monodispersed polystyrene (PS)/poly(n-butyl methacrylate) (PBMA) composite particles having 9.4 μm in diameter were produced by seeded polymerization for the dispersion
of highly n-butyl methacrylate (BMA)-swollen PS particles, and their morphologies were examined. The highly BMA-swollen PS particles
(about 150 times the weight of the PS seed particles) were prepared by mixing monodispersed 1.8 μm-sized PS seed particles
and 0.7 μm sized BMA droplets prepared with an ultrasonic homogenizer in ethanol/water (1/2, w/w) medium at room temperature.
After NaNO2 aqueous solution as inhibitor was added in the dispersion, the seeded polymerization was carried out at 70 °C. In an optical
microscopic observation, one or two spherical high contrast regions which consisted mainly of PS were observed inside PS/PBMA
composite particles. In the PS domain, there were many fine spherical PBMA domains. Such morphologies were based on the phase
separation of PS and PBMA within the homogeneous swollen particles during the seeded polymerization.
Received: 04 June 1997 Accepted: 27 August 1997 相似文献
5.
Micron-sized monodispersed polymethyl methacrylate (PMMA)/polystyrene (PS) (PMMA/PS=2/1, wt ratio) composite particles consisting
of PMMA-core and PS-shell were successfully produced by seeded dispersion polymerization of styrene in a methanol/water medium
in the presence of about 2 μm-sized monodispersed PMMA particles. From the view point of thermodynamic equilibrium, such a
morphology is difficult to form by usual seeded polymerization in a polar medium such as water. It is concluded that seeded
dispersion polymerization in which almost all monomers and initiators exist in the medium has an advantage to produce core/shell
polymer particles in which polymer layers accumulate in their order of the production regardless of the hydrophobicity of
polymers, because of high viscosity in polymerizing particles.
Received: 9 December 1996 Accepted: 26 February 1997 相似文献
6.
Formation mechanism of micron-sized monodispersed polymer particles having a hollow structure 总被引:1,自引:0,他引:1
Recently, the authors reported that micron-sized monodispersed cross-linked polymer particles having a single hollow in the
inside were produced by seeded polymerization for the dispersion of (toluene/divinylbenzene)-swollen polystyrene (PS) particles
prepared utilizing the dynamic swelling method which the authors had proposed. In this article, the particles at various conversions
of the seeded polymerization were observed with an optical microscope in detail. From the obtained results, the formation
mechanism of the hollow structure is suggested as follows. As seeded polymerization proceeds, poly-divinylbenzene (PDVB) molecules
precipitated in the swollen particle are trapped near the interface and gradually pile at the inner surface, which results
in a cross-linked PDVB shell. PS which dissolves in the swollen particles is repelled gradually to the inside. After the completion
of the polymerization, toluene in the hollow evaporates by drying, and PS clings to the inner wall of the shell uniformly.
Received: 14 February 1997 Accepted: 16 April 1997 相似文献
7.
Micron-sized monodispersed polystyrene (PS)/poly(n-butyl methacrylate) composite particles were produced as follows. First, 1.77 μm-sized monodispersed PS seed particles produced
by dispersion polymerization were dispersed in ethanol/water (1/2, w/w) medium dissolving poly(vinyl alcohol) as a stabilizer.
n-Butyl methacrylate (BMA) monomer dissolving benzoyl peroxide initiator was emulsified in ethanol/water (1/2, w/w) solution
of sodium dodecyl sulfate as emulsifier with ultrasonic homogenizer, and the BMA monomer emulsion was mixed with the PS seed
emulsion. The PS seed particles absorbed with a large amount of BMA (about 150 times weight of the seed particles) for 2 h
to about 10 μm in diameter while keeping good monodispersity and BMA droplets disappeared finally. The seeded polymerization
was carried out at 70 °C after a certain amount of water was added to depress the redissolving of BMA from the swollen particles
into the medium by raising from room temperature to the polymerzation temperature.
Received: 21 February 1996 Accepted: 4 September 1996 相似文献
8.
Recently, we found that “golf ball”-like polystyrene (PS)/polybutyl acrylate (PBA) composite particles could be produced
by seeded emulsion polymerization of butyl acrylate (BA) with PS seed particles. In this article, the effects of the polymerization
temperature, BA monomer concentration, and the presence of 1-octanol, which is a good solvent for PBA and a poor solvent for
PS in the polymerization, on the morphology was studied.
Received: 25 February 1997 Accepted: 4 October 1997 相似文献
9.
Micron-sized, monodispersed polystyrene (PS)/poly (n-butyl methacrylate) (PBMA) composite particles, in which the PS domain(s) were dispersed in a PBMA continuous phase, were
produced by seeded polymerization for dispersions of n-butyl methacrylate (BMA) swollen PS particles in a wide range of PS/BMA ratios in the presence of NaNO2 as a water-soluble inhibitor. Moreover, in order to change the diameter of the composite particles at same PS/BMA ratio,
PS/PBMA (1/150 w/w) composite particles were produced using five kinds of PS particles in a range of diameters from 0.64 to
3.27 μm as seeds. The percentages of the PS/PBMA composite particles having double and triple and over PS domains, which were
thermodynamically unstable morphologies, increased with the increase in the diameter of BMA swollen PS particles. There was
a clear influence of the size of the swollen particles on the morphology of the PS/PBMA composite particles produced.
Received: 30 September 1999/Accepted: 18 April 2000 相似文献
10.
C.-F. Lee 《Colloid and polymer science》2002,280(2):116-123
Composite polymer particles which contain poly(methyl methacrylate) (PMMA) and polystyrene (PS) components (PMMA/PS composite
particle) were synthesized by the method of multistage soapless seeded emulsion polymerization. In this study, the process
of multistage soapless seeded emulsion polymerization included two-stage polymerization, three-stage polymerization or four-stage
polymerization. The morphologies of the PMMA/PS composite particles were studied. The kinetic factor was the main force to
control the morphology of the linear PMMA–PS composite particles which were synthesized by the method of two-stage reaction.
Both the kinetic factor and the thermodynamic factor decide the morphology of the linear composite particles which were synthesized
by the method of either three-stage or four-stage reaction. However, the thermodynamic factor cannot influence the morphology
of the PMMA/PS composite particles with a cross-linked structure which were synthesized by the method of three-stage reaction.
The cross-linked composite polymer particles had the morphology of a multilayer structure, which showed that the polymer layers
accumulated in their order of production.
Received: 9 January 2001 Accepted: 14 June 2001 相似文献
11.
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
12.
Micron-sized, monodispersed, poly(methyl methacrylate) (PMMA)/polystyrene (PS)/PMMA/PS multilayered composite particles were
successfully produced by three-step seeded dispersion polymerizations in methanol/water media. The first seeded dispersion
polymerization was carried out with 2-μm-sized, monodispersed PMMA particles. 相似文献
13.
Summary: Submicron-sized monodisperse PS particles were prepared by dispersion polymerization of styrene in ionic liquids with poly(vinylpyrrolidone) as stabilizer. Seeded dispersion polymerization of MMA was subsequently carried out with PS seeds in [Bmim][BF4] to prepare PS/PMMA composite particles. Observation of the obtained particles of ultrathin cross-sections with a scanning and transmission electron microscope revealed that no secondary nucleation occurred during the seeded dispersion polymerization and that the particles have a core-shell morphology consisting of a PS core and a PMMA shell. Successful preparation of PS/PMMA composite particles in an ionic liquid has thus been demonstrated. Moreover, PS/PAA (PS-core/PAA-shell) composite particles were prepared by seeded dispersion polymerization in [DEME][TFSI], illustrating that hydrophobic/hydrophilic composite particles can be readily prepared in the ionic liquid. 相似文献
14.
Micron-sized monodispersed polystyrene (PS)/poly(3,5-xylidine) (PXy) composite particles were produced by chemical oxidative
seeded dispersion polymerization of 3,5-xylidine at 20 °C with 1.6-μm-sized monodispersed PS seed particles in HCl aqueous
solution, the pH of which was always kept at 2.5 with a pH stat. The composite particles produced consisted of a PS core and
a PXy shell.
Received: 16 December 1998 Accepted in revised form: 25 March 1999 相似文献
15.
Recently, we found that “golf-ball-like” polystyrene (PS)/poly(butyl acrytlate) composite particles could be produced by
seeded emulsion polymerization of butyl acrylate with PS seed particles. In this article, the theoretical and experimental
thermodynamic instabilities of the golf-ball-like structure are discussed and are compared with core-shell and hemispherical
morphologies.
Received: 2 February 1999 Accepted in revised form: 3 June 1999 相似文献
16.
Micron-sized, monodispersed, electrically conductive polystyrene (PS)/polyaniline (PAn) composite particles were produced
by chemical oxidative seeded dispersion polymerization of aniline at 0 °C with 1.37-μm-sized, monodispersed PS seed particles
in HCl aqueous solution, where the pH value was kept at 2.5 with a pH stat. The composite particles consisted of a PS core
and a PAn shell. A pellet of the composite particles had a conductivity of 3.4 × 10−3 S/cm.
Received: 5 April 2000 Accepted: 10 August 2000 相似文献
17.
A flexible poly(dimethyl siloxane) diacrylate (PDMSDA) crosslinker was synthesized using different molecular weights of poly(dimethyl siloxane) (PDMS, M
n
=550, 1,700, 4,000 g/mol). The monodisperse polystyrene (PS) particles crosslinked with various contents of PDMSDA were prepared by dispersion polymerization, and applied as seed particles in the seeded polymerization. The crosslinking density of the PS particles was determined from the rate of transport of the monomer molecules to the crosslinked seed particles. It was confirmed that the monomer swelling capacity of seed particles and final morphological changes of polymer beads were determined significantly by the crosslinking density of the seed particles. In addition, the morphological change was not observed without the oligomer swelling step in the seeded polymerization due to the hydrophobic property of PDMS. When highly crosslinked seed particles were used in the seeded polymerization, peculiar morphology (doublet structure) of polymer beads appeared. 相似文献
18.
Production of micron-sized monodispersed core/shell composite polymer particles by seeded dispersion polymerization 总被引:1,自引:0,他引:1
The effect of the weight ratio of seed polymer/monomer on the morphology of the poly(methyl methacrylate) (PMMA)/polystyrene
(PS) monodispersed composite particles produced by batch seeded dispersion polymerization of styrene with 1.64-μm-sized monodispersed
PMMA seed particles in a methanol/water medium (4/1 w/w) was examined. In the PMMA/PS weight ratios of 3/1 and 2/1, the composite
particles had a clear morphology consisting of a PMMA core and a PS shell. In the ratio of 1/1, a lot of small PS domains
were observed in the PMMA core though the PS shell was still formed. By stepwise addition of styrene monomer, the formation
of the small PS domain was depressed and complete core/shell morphology was formed. Absorption/release treatments of toluene
into/from the PMMA/PS (1/1 w/w) composite particles resulted in a drastic morphological change from the core/shell structure
to a multi- layered one.
Received: 2 February 1999 Accepted in revised form: 7 April 相似文献
19.
Xiao-ping Chen Kun-yuan Qiu Department of Polymer Science Engineering College of Chemistry Peking University Beijing China 《高分子科学》2000,(2):149-153
"Living"/controlled radical polymerization of ethyl methacrylate (EMA) was carried out with a 2,2'-azobisisobutyronitrile (AIBN)/ferric chloride (FeCl_3)/triphenylphosphine (PPh_3) initiation system at 85℃. Thc numberaverage molecular weight (M_n) increases linearly with monomer conversion and the rate of polymerization is first order withrespect to monomer concentration. The M_w of PEMA ranges from 3900 to 17600 and the polydispersity indices are quitenarrow (1.09~1.22). The conversion can reach up to~100% and M_w of the polymers obtained is close to that designed. Thepolymerization mechanism belongs to the reverse atom transfer radical polymerization (ATRP). The polymer was end-functionalized by chlorine atom, which acts as a macroinitiator to proceed extension polymerization in the presence ofCuBr/bipy catalyst system via an ATRP process. The presence of ω-chlorine in the PEMA obtained was identified by ~1H-NMR spectrum. 相似文献
20.
Teruhisa Fujibayashi Takuya Tanaka Hideto Minami Masayoshi Okubo 《Colloid and polymer science》2010,288(8):879-886
Micrometer-sized, monodisperse, “hamburger-like” polystyrene (PS)/poly(2-ethylhexyl methacrylate)/decane composite particles
were obtained by seeded dispersion polymerization of 2-ethylhexyl methacrylate with PS seed particles in the presence of decane.
The morphological stability of the hamburger-like particles was investigated based on thermodynamic and kinetic aspects. The
hamburger-like morphology was maintained at 60 °C (above glass transition temperature (T
g)) for at least 1 week in spite of less thermodynamic stability than hemispherical morphology. T
g of the particles gradually increased throughout the polymerization due to monomer consumption. Geometric calculation result
indicates that the degree of reduction of the interfacial free energy at the early stage of the morphological development
is significantly low. From these results, it is concluded the morphological stability of the hamburger-like particles is considerably
high because the development from hamburger-like to hemispherical morphologies is retarded by the gradual increase in viscosity
inside the particles and the significantly lower interfacial free energy reduction. 相似文献