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ABSTRACT: In a mixed solvent of water and ethanol, polystyrene/titanium dioxide (PSt/TiO2) composite particles of core-shell structure were prepared by hydrolysis of tetrabutyl titanate in the presence of cationic PSt particles or anionic PSt particles surface-treated using gamma-aminopropyl triethoxysilane. Hollow TiO2 particles were obtained through calcination of the PSt/TiO2 core-shell particles to burn off the PSt core or through dissolution of the core by tetrahydrofuran (THF). An alternative process constituted of preheating the PSt/TiO2 particles at 200[degree sign]C to allow partial crystallization followed by calcination or PSt dissolution by THF. The outcome TiO2 particles thus prepared were examined by TEM, and hollow TiO2 particles were observed. The crystalline phase structure and phase transformation were characterized, which revealed that preheating before the removal of the PSt core was useful to achieve the desired hollow TiO2 particles, and the calcination process was beneficial to the formation of anatase and rutile structures. The tests of TiO2 particles as catalyst in the photodegradation of Rhodamine B demonstrated that a much higher catalytic activity was observed with the TiO2 hollow particles prepared through calcination combined with preheating.
Nanoscale Research Letters 11/2012; 7(1):646. · 2.73 Impact Factor
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ABSTRACT: Monodisperse polydivinylbenzene (PDVB) microspheres with clean surface were prepared by precipitation polymerization without
stabilizer in supercritical carbon dioxide using acetone as cosolvent. Effects of the cosolvent, reaction time and pressure,
and monomer concentration on the polymerization were studied. It was found that the conversions in all polymerization systems
were above 95%. Examination by scanning electron microscopy showed that reaction pressure, divinylbenzene concentration, and
level of the cosolvent had pronounced effects on the morphology of the microspheres. When 6 ∼ 7ml of acetone was used in
a reactor of 50ml, monodisperse PDVB microspheres of around 2.1μm in diameter were obtained. Thermal gravimetrical analysis
showed the products were of good thermostability up to about 400°C.
KeywordsMorphology-Particle size distribution-Polydivinylbenzene-Precipitation polymerization-Supercritical carbon dioxide
Colloid and Polymer Science 05/2012; 288(16):1571-1580. · 2.33 Impact Factor
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ABSTRACT: Hydrophobically modified alkali-soluble acrylic latexes were prepared using varying level of SEM-25, triphenylethyl phenoxy
polyoxyethylene ether methacrylate, a functional monomer bearing a long segment of ethylene oxide and a hydrophobic tetraphenyl
group. Sharp increases in viscosity and light transmittance of the diluted associative thickener latexes were observed with
ascendant pH starting from 7. And with further increase in the pH, viscosity of the thickener latexes rapidly fell down, while
the light transmittance was kept relatively constant. It was revealed that a critical content of SEM-25 in the thickener copolymer,
5% in the present case, was required in order for the associative thickener to outperform the SEM-25 free counterpart. When
used in thickening a latex of P(St–BA) (Poly(styrene–Butyl acrylate)) copolymer using a thickener copolymer with 12wt% of
SEM-25, addition of 0.34wt% of the thickener polymer relative to P(St–BA) was necessary to have a higher viscosity than the
same latex thickened using the thickener free of SEM-25. It seemed that incorporation of 0.275mol% of SEM-25 was indispensable
for the associative thickener to exceed the performance of conventional thickener.
KeywordsSEM-25 functional monomer-Hydrophobic group-Associative thickener-Light transmittance-Rheological property
Polymer Bulletin 04/2012; 64(7):677-690. · 1.53 Impact Factor
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Macromolecular Chemistry and Physics 09/2010; 211(20):2201 - 2210. · 2.36 Impact Factor
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ABSTRACT: With dodecanol (C12OH) as a model molecule of insect sex pheromone as core material, natural polymers gelatin (GE) and acacia gum (AG) as wall materials, microcapsules aiming to be a sprayable environment-friendly pesticide were prepared via GE simple coacervation and complex coacervation of GE and AG. C12OH encapsulation in complex coacervation was higher than those in simple coacervation. Its encapsulation was enhanced with increase in wall material cross-linking. C12OH release revealed that samples from simple coacervation reached their end in 7 days, whereas those from complex coacervation manifested a quick release followed by a constant release. With increase in wall material cross-linking, the release was slowed down. SEM observation confirmed that core-shell morphology existed in the capsules.
Journal of Microencapsulation 02/2010; 27(4):355-64. · 1.55 Impact Factor
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ABSTRACT: The precipitation polymerization of styrene-trihydroxymethyl propane triacrylate has been carried out using ethanol and an ethanol/water mixture as the solvent. Uniform microspheres with high monomer conversion are achieved within 4 h, a much shorter polymerization time than that reported for the precipitation polymerization of divinyl benzene-styrene in acetonitrile. The results clearly demonstrate that use of water as a co-solvent is indeed very effective to promote the polymerization to high conversion and to obtain uniform microspheres. With no water under the otherwise same experimental conditions, only about 57% of monomer conversion is obtained; while the monomer conversion is remarkably increased to 96% when 12 vol.-% of water is used.
Macromolecular Rapid Communications 06/2009; 30(11):909-14. · 4.60 Impact Factor
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ABSTRACT: Using insect female pheromone to disrupt their mating process is a new technology, which has been applied as environment friendly pesticides in agricultural and forestry industries to control pest infestation. Dodecanol (C(12)OH), as one of the simple pheromone component, was chosen and encapsulated as core material using gelatin (GE) and acacia gum (AG) as wall materials via complex coacervation. Through variations in capsule preparations, particularly the crosslinking density of the wall materials, release controllability of C(12)OH was studied. A series of C(12)OH-containing capsules were prepared with different concentrations of GE and AG and different crosslinkings. Crosslinking and C(12)OH encapsulation were enhanced when more crosslinker, either formaldehyde or glutaraldehyde, were used. At same level of crosslinker, lower crosslinking and higher C(12)OH encapsulation were obtained in microcapsules done with formaldehyde than those with glutaraldehyde. Constant release of C(12)OH was achieved in capsules prepared with glutaraldehyde. Mechanisms of C(12)OH release were discussed based on the results. Scanning electron microscopy was used to characterize the structure and morphology of the microcapsules, which seemingly confirmed existence of a core-shell structure in the capsules, with the coacervated polymers as the shell and C(12)OH the core.
Biomedical Microdevices 10/2008; 11(1):275-85. · 3.03 Impact Factor
