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1.
Recently, we reported that multi-hollow polymer particles can be prepared from carboxylated polymer particles by the stepwise
alkali/acid method. In this article, an attempt was made to prepare similar particles from acid-swellable polymer particles
by the stepwise treatment with acid and alkali, which was named the stepwise acid/alkali method. The acid-swellable particles
were produced by emulsion terpolymerization of styrene, butyl acrylate, and dimethyl 2-amino ethyl methacrylate. The effects
of initial pH value, temperature, and time in the acid and alkali treatment processes on the multi-hollow structure were examined.
Received: 18 December 1996 Accepted: 11 March 1997 相似文献
2.
J. Pablo Tomba Daniel Portinha Walter F. Schroeder Mitchell A. Winnik Willie Lau 《Colloid and polymer science》2009,287(3):367-378
This paper describes experiments that investigate the use of low glass transition temperature (T
g) latex particles consisting of oligomer to promote polymer diffusion in films formed from high molar mass polymer latex.
The chemical composition of both polymers was similar. Fluorescence resonance energy transfer (FRET) was used to follow the
rate of polymer diffusion for samples in which the high molar mass polymer was labeled with appropriate donor and acceptor
dyes. In these latex blends, the presence of the oligomer (with M
n = 24,000 g/mol, M
w/M
n = 2) was so effective at promoting the interdiffusion of the higher molar mass poly(butyl acrylate-co-methyl methacrylate; PBA/MMA = 1:1 by weight) polymer (with M
n = 43,00 g/mol, M
w/M
n = 3) that a significant amount of interdiffusion occurred during film drying. Additional polymer diffusion occurred during
film aging and annealing, and this effect could be described quantitatively in terms of free-volume theory.
This paper is dedicated to Professor Haruma Kawaguchi to honor his many contributions to the field of latex particles and
their applications. 相似文献
3.
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
4.
Carlos Kleber Z. Andrade Ricardo Alexandre F. Matos Viviane B. Oliveira Jussara A. Durães Maria J. A. Sales 《Journal of Thermal Analysis and Calorimetry》2010,99(2):539-543
Thermal properties of new ionic liquids (ILs) were investigated by thermogravimetry (TG/DTG) and differential scanning calorimetry
(DSC). Chlorides, tetrafluoroborates and hexafluorophosphates of (−)mentholpyrrolidinium and (−)-mentholimidazolium cations
revealed good thermal stability at air atmosphere. Morphological characteristics of poly(methyl methacrylate) (PMMA) matrices
doped with 10% of these ILs were also investigated by DRX and water absorption test. Into the matrix, they exhibited a very
satisfactory pattern concerning the polymer thermal stabilization. DSC results show that some of these ILs also present plasticizer
features since they can lower the polymer glass transition temperature (T
g) up to 317.15 K. 相似文献
5.
Effect of polymer composition on the production of cationic multihollow polymer particles by the stepwise acid/alkali method 总被引:3,自引:0,他引:3
The effect of the polymer composition on the formation of multihollow structures formed within submicron-sized styrene–butyl
acrylate–dimethylaminoethyl methacrylate terpolymer particles by the “acid/alkali method” proposed by the authors was examined.
The cationic particles were produced by seeded emulsion terpolymerization with 2,2′-azobis(2-amidinopropane) hydrochloride
initiator. The dimethylaminoethyl methacrylate content and the glass-transition temperature of the terpolymer greatly affected
the formation of the multihollow structure.
Received: 3 December 1998 Accepted in revised form: 4 February 1999 相似文献
6.
Evaporation behavior of water from aqueous dispersions of multihollow particles prepared by the stepwise alkali/acid method 总被引:1,自引:0,他引:1
In order to clarify the formation mechanism of multihollow structures inside styrene–methacrylic acid copolymer particles
prepared by the stepwise alkali/acid method, which we proposed in 1990, the evaporation behavior of water from aqueous dispersions
of the original carboxylated particles and those after the alkali treatment and the stepwise alkali/acid treatments was examined.
It is concluded that the particle after the alkali treatment had a number of small water pools inside.
Received: 22 February 2001 Accepted: 20 June 2001 相似文献
7.
Core–shell latex particles made of a poly(butyl methacrylate) (PBMA) core and a thin polypyrrole (PPy) shell were synthesized
by two-stage polymerization. In the first stage, PBMA latex particles were synthesized in a semicontinuous process by free-radical
polymerization. PBMA latex particles were labeled either with an energy donor or with an energy acceptor, in two different
syntheses. These particles were used in a second stage as seeds for the synthesis of the core–shell particles. The PPy shell
was polymerized around the PBMA core latex in an oxidative chemical in situ polymerization. Proofs for the success of the
core–shell synthesis were obtained using nonradiative energy transfer (NRET) and atomic force microscopy (AFM). NRET gives
access to the rate of polymer chain migration between adjacent particles in a film annealed at a temperature above the glass-transition
temperature T
g of the particles. Slower chain migration of the PBMA polymer chains was obtained with the PBMA–PPy core–shell particles compared
to rate of the PBMA polymer chain migration found with the pure, uncoated PBMA particles. This result is due to the coating
of PBMA by PPy, which hinders the migration of the PBMA polymer chains between adjacent particles in the film. This observation
has been confirmed by AFM measurements showing that the flattening of the latex film surface is much slower for the core–shell
particles than for the pure PBMA particles. This result can again be explained by the presence of a rigid PPy shell around
the PBMA core. Thus, these two complementary methods have given evidence that real core–shell particles were synthesized and
that the shell seriously hinders film formation of the particles in spite of the fact that it is very thin (thickness close
to 1 nm) compared to the size (750 and 780 nm in diameter) of the PBMA core. Transparency measurements confirm the results
obtained by NRET and AFM. When the films are placed at a temperature higher than the T
g of PBMA, the increase in transparency is faster for films made with the uncoated PBMA particles than for films made with
the coated PBMA particles. This result indicates again that the presence of the rigid PPy layer around the PBMA core reduces
considerably the speed at which the structure of the film is modified when heated above the T
g of PBMA.
Received: 02 September 1999 Accepted: 21 December 1999 相似文献
8.
The effects of nonionic emulsifier on the formation of multihollow structures formed within sub-micron-sized polymer particles by the “acid/alkali method” proposed by the authors were examined. The original acid-swellable particles were produced by seeded emulsion terpolymerization of styrene, butyl acrylate, and dimethylaminoethyl methacrylate. The results indicate that the nonionic emulsifier had a great effect on the formation of multihollow particles. 相似文献
9.
Zheyu Shen Ken Terao Yasuyuki Maki Toshiaki Dobashi Guanghui Ma Takao Yamamoto 《Colloid and polymer science》2006,284(9):1001-1007
Poly(N-isopropylacrylamide) (PNIPAM) and random copolymers of Poly(N-isopropylacrylamide-co-2-hydroxyethyl methacrylate) (PNIPAM-HEMA), poly(N-isopropylacrylamide-co-acrylamide) (PNIPAM-AAm), and poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) (PNIPAM-DMAA) with various volume fractions γ of NIPAM were synthesized by radical polymerization. The phase behavior of the polymers in water was investigated by means of optical transmittance and dynamic light scattering. With decreasing γ, the cloud point temperature T
cp for PNIPAM-HEMA decreased whereas the T
cp for both PNIPAM-AAm and PNIPAM-DMAA increased. Increase of hydrodynamic radius around T
cp, which resulted from the aggregation of the globules of each polymer, was observed from dynamic light scattering. The relationships between the reciprocal of T
cp of the polymer solutions and 1-γ were linear for the three copolymers in the experimental range of 0.65<γ<1. The results are discussed from the aspect of the interaction parameters of copolymer solutions. 相似文献
10.
Shuhei Yamada Zhifeng Wang Emiko Mouri Kohji Yoshinaga 《Colloid and polymer science》2009,287(2):139-146
We report a novel strategy for incorporation of titanium dioxide (TiO2) particles, which were crystallized from peroxotitanic acid in the presence of hydrophilic polymer by hydrothermal treatment
in aqueous solution, into poly(methyl methacrylate) (PMMA) via dispersion into chloroform. Dispersion of TiO2 particles into chloroform was achieved by solvent change from water to chloroform in aid of amphiphilic polymer dispersant,
poly(N-vinyl pyrrolidone) (PVP), poly(N-vinyl pyrrolidone-co-methyl methacrylate) (PVP-co-PMMA), poly(N-vinyl pyrrolidone-block-methyl methacrylate) (PVP-b-PMMA) through azeotropical removal of water. Incorporation of TiO2 particles into PMMA was carried out by a casting process of a mixture of TiO2 particles dispersed with PVP154-b-PMMA156 in chloroform and PMMA on a glass substrate. Resultant hybrid film containing TiO2 less than 10 wt.% showed high transparency in visible region attributable to homogeneous dispersion into PMMA matrix. The
refractive index of the hybrid films increased with TiO2 content and agreed with the calculated values. 相似文献
11.
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
12.
A. Yu. Men’shikova K. S. Inkin T. G. Evseeva Yu. O. Skurkis B. M. Shabsel’s N. N. Shevchenko S. S. Ivanchev 《Colloid Journal》2011,73(1):76-82
Emulsifier-free emulsion copolymerization of methyl methacrylate with N-vinylformamide and glycidyl methacrylate initiated by a cationic or anionic azoinitiator in the presence of dextran is used
to produce monodisperse polymer particles with a developed multifunctional surface. As a result, monodisperse particles are
obtained with a diameter of 350–660 nm, the surface layer of which contains, in addition to carboxyl groups, amino or epoxy
groups. The conditions are determined for the formation of multifunctional hydrophilic particle surface via the hydrolysis
of comonomer units and residual groups of initiators. The limiting values of bovine serum albumin chemisorption (2.4 and 1.0
mg/m2 on the particles of methyl methacrylate copolymers with glycidyl methacrylate or N-vinyl formamide, respectively) indicate that the obtained particles have sufficient sorption capacity to be applied as carriers
for immunoreagents. 相似文献
13.
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
14.
Dong Woo Cho Kyoung Shil Oh Won Bae Hwayong Kim Youn-Woo Lee 《Colloid and polymer science》2009,287(2):179-188
In this study, monodispersed spherical particles of poly(acrylonitrile) were synthesized via dispersion polymerization in
compressed liquid dimethyl ether using 2,2′-azobisisobutyronitrile (AIBN) as an initiator and five kinds of surfactants: PDMS-g-pyrrolidonecarboxylic acid (Monasil PCA™), PDMS modified surfactants, SS-5050K™, KF-6017™, poly(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-
heptadecafluorodecyl acrylate), and poly(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl methacrylate). Using Monasil
PCA as a surfactant, uniform and spherical polymer particles were generated. The size of the microsphere particles was reduced
via an increase in the concentration of Monasil PCA and a reduction in the monomer concentration. Increases in the concentration
of AIBN resulted in a broad distribution of microspheres. Reaction temperature and pressure did not exert significant effects
on the size and size distribution of the polymer particles. 相似文献
15.
The alkalization of carboxylated acrylic polymer latexes by sodium hydroxide gives rise to swelling of the particles. For
a poly(n-butyl acrylate) latex copolymerized with 15 wt % methacrylic acid (MAA) and 7 wt % acrylonitrile the particle volume increases
by a factor of 30. The alkali-swelling does not depend on the type of monovalent cation used in the base (LiOH, NaOH, KOH,
NH4OH). In contrast, when bivalent cation bases such as Ca(OH)2 are employed no latex swelling is observed during neutralization because of ionic crosslinking of the copolymer chains. Crosslinking
also takes place when the bivalent cations (Ca2+, Zn2+, Mg2+) are added as chlorides to dispersions with latexes previously swollen by sodium hydroxide. In these experiments the original
size of the latexes is reached again at a molar ratio MAA: bivalent metal ion of 2:1, i.e. at charge compensation of the carboxyl
groups. The shrinking behavior is almost independent of the type of bivalent metal ion used. On the other hand, it is more
pronounced when trivalent cations such as Fe3+ are added. In general, the experiments demonstrate that the alkali swelling of acrylic latexes is dominated by electrostatic
forces.
Received: 18 August 1998 Accepted in revised form: 26 October 1998 相似文献
16.
Masayoshi Okubo Akira Ito Masahiro Okada Toyoko Suzuki 《Colloid and polymer science》2002,280(6):574-578
The variation of the morphology of a carboxylated polymer film cast from tetrahydrofuran solution, in which styrene/methacrylic acid copolymer particles produced by emulsion copolymerization were dissolved, before and after alkali treatment at temperatures higher than the glass-transition temperature was observed with a scanning electron microscope. The treated film had a porous structure. This result provides important evidence for the formation mechanism of the multihollow structure in submicron-sized, carboxylated polymer emulsion particles by the stepwise alkali/acid method and the alkali/cooling method which the authors proposed. 相似文献
17.
Ideal Behavior of Water Solutions of Strong Electrolytes and Non-electrolytes at High Concentrations
Andreas A. Zavitsas 《Journal of solution chemistry》2010,39(3):301-317
Contrary to widely held beliefs, many concentrated aqueous solutions of strong electrolytes and nonelectrolytes are shown
to behave ideally by calculating the activity of water (a
w) from vapor pressure data. The mole fraction of water (x
w) is equal to the water activity a
w(Raoult’s Law) when the mole fraction of water is calculated by accounting for water strongly bound to the solute, which is
then not available to act as solvent. In this case x
w=(55.51−mH
T)/(55.51−mH
T+im), where m is the molality of the solute particles, i is the stoichiometric number of solute particles produced per mole of dissolved solute, and H
T is the thermodynamic hydration number H
T. Published reservations about previous work of this type are addressed. The values of H
T vary little over wide ranges of concentration and correlate with the Hofmeister series, the B coefficient of the Jones-Dole viscosity equation, and other properties of water. Activity coefficients of the bulk or “free”
water remain at unity even at high concentrations. 相似文献
18.
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
19.
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
20.
According to the new method of preparing core-shell nanospheres developed by our group, by using two monomers, 2-hydroxypropyl
methacrylate(HPMA) and vinyl acetate(VAc), two kinds of core-shell nanospheres with poly(ɛ-caprolactone) (PCL) as the core
and crosslinked poly(2-hydroxypropyl methacrylate) (PHPMA) or poly(vinyl acetate) (PVAc) as the shell were successfully prepared
under similar conditions. After degrading the PCL cores of the two kinds of nanospheres by lipase, the corresponding crosslinked
poly(methyl acrylic acid) hollow spheres and crosslinked poly(vinyl alcohol) hollow spheres were obtained. Results indicate
that the new method we proposed for preparing core-shell polymeric nanospheres via in-situ polymerization can be generalized to a certain extent, and it is suitable for many systems provided the monomer used is soluble
in water, while its corresponding polymer is insoluble in water.
Translated from Chemical Journal of Chinese University, 2006, 27(9): 1762–1766 [译自: 高等学校化学学报] 相似文献