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101.
Poly(vinyl alcohol) (PVA) was used as a steric stabilizer for the dispersion polymerization of cross-linked poly(N-isopropylacrylamide) (PNIPAM) in water. A series of reactions were carried out using PVA of varying molecular weight and degree of hydrolysis. Under appropriate conditions, PNIPAM particles of uniform and controllable size were produced using PVA as the stabilizer. The colloidal stability was investigated by measuring changes in particle size with temperature in aqueous suspensions of varying ionic strength. For comparison, parallel colloidal stability measurements were conducted on PNIPAM particles synthesized with low-molecular-weight ionic surfactants. PVA provides colloidal stability over a wide range of temperature and ionic strength, whereas particles produced with ionic surfactants flocculate in moderate ionic strength solutions upon collapse of the hydrogel as the temperature is increased. Experimental results and theoretical consideration indicate that sterically stabilized PNIPAM particles resulted from the grafting of PVA to the PNIPAM particle surface. The enhanced colloidal stability afforded by PVA allows the temperature-responsive PNIPAM particles to be used under physiological conditions where electrostatic stability is ineffective. 相似文献
102.
Ching-Chun Tsai 《Polymer Degradation and Stability》2010,95(8):1292-4984
Transparent biaxial oriented poly(lactic acid) (BOPLA) films with improved dimensional stability were successfully prepared by controlling the crystallization of poly(lactic acid) (PLA). The crystalline morphology of PLA films can be manipulated by changing certain processing parameters, such as stretch ratio, heat setting temperatures, and heat setting time. Optical and mechanical properties as well as dimensional stability of the resulting polymer films are governed by their crystallinity and crystalline morphology. Crystallization behavior and kinetics of PLA, therefore, were investigated using wide angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS), and differential scanning calorimetry (DSC) techniques. Mechanical properties and the dimensional stability of the biaxial oriented PLA films were obtained and correlated with their processing conditions. Poly(lactic acid) films prepared by melt extrusion methods have great potential for food packaging, shrink labeling and protective film applications. However, shrinkage at elevated processing temperature should be minimized to avoid puckering of the polymer film. Shrinkage of less than 2% was achieved for a BOPLA film stretched 300% in both directions at 75 °C and then annealed at 160 °C for 30 s. Fabrication, properties, and potential applications of a series of biodegradable films will be described. 相似文献
103.
Jen-Yi Hsu Jing-Fang Hsu Yet-Ran Chen Chia-Lang Shih Yi-Sheng Hsu Yi-Jen Chen Shu-Han Tsai Pao-Chi Liao 《Analytica chimica acta》2016
Human biomonitoring is the assessment of actual internal contamination of chemicals by measuring exposure markers, chemicals or their metabolites, in human urine, blood, serum, and other body fluids. However, the metabolism of chemicals within an organism is extremely complex. Therefore, the identification of metabolites is often difficult and laborious. Several untargeted metabolomics methods have been developed to perform objective searching/filtering of accurate-mass-based LC-MS data to facilitate metabolite identification. In this study, three metabolomics data processing approaches were used for chemical exposure marker discovery in urine with an LTQ-Orbitrap high-resolution mass spectrometry (HRMS) dataset; di-isononyl phthalate (DINP) was used as an example. The data processing techniques included the SMAIT, mass defect filtering (MDF), and XCMS Online. Sixteen, 83, and 139 probable DINP metabolite signals were obtained using the SMAIT, MDF, and XCMS procedures, respectively. Fourteen probable metabolite signals mined simultaneously by the three metabolomics approaches were confirmed as DINP metabolites by structural information provided by LC-MS/MS. Among them, 13 probable metabolite signals were validated as exposure-related markers in a rat model. Six (m/z 319.155, 361.127, 373.126, 389.157, 437.112 and 443.130) of the 13 exposure-related DINP metabolite signals have not previously been reported in the literature. Our data indicate that SMAIT provided an efficient method to discover effectively and systematically urinary exposure markers of toxicant. The DINP metabolism information can provide valuable information for further investigations of DINP toxicity, toxicokinetics, exposure assessment, and human health effects. 相似文献
104.
Improvement of the Water Resistance of a Narrow‐Band Red‐Emitting SrLiAl3N4:Eu2+ Phosphor Synthesized under High Isostatic Pressure through Coating with an Organosilica Layer 下载免费PDF全文
Dr. Yi‐Ting Tsai Dr. Hoang‐Duy Nguyen Dr. Agata Lazarowska Dr. Sebastian Mahlik Prof. Dr. Marek Grinberg Prof. Dr. Ru‐Shi Liu 《Angewandte Chemie (International ed. in English)》2016,55(33):9652-9656
A SrLiAl3N4:Eu2+ (SLA) red phosphor prepared through a high‐pressure solid‐state reaction was coated with an organosilica layer with a thickness of 400–600 nm to improve its water resistance. The observed 4f65d→4f7 transition bands are thought to result from the existence of Eu2+ at two different Sr2+ sites. Luminescence spectra at 10 K revealed two zero‐phonon lines at 15377 (for Eu(Sr1)) and 15780 cm?1 (for Eu(Sr2)). The phosphor exhibited stable red emission under high pressure up to 312 kbar. The configurational coordinate diagram gave a theoretical explanation for the Eu2+/3+ result. The coated samples showed excellent moisture resistance while retaining an external quantum efficiency (EQE) of 70 % of their initial EQE after aging for 5 days under harsh conditions. White‐light‐emitting diodes of the SLA red phosphor and a commercial Y3Al5O12:Ce3+ yellow phosphor on a blue InGaN chip showed high color rendition (CRI=89, R9=69) and a low correlated color temperature of 2406 K. 相似文献
105.
Chia-Jung Tsai 《European Polymer Journal》2008,44(7):2339-2347
Poly(ethylene succinate) (PES), poly(trimethylene succinate) (PTS) and their copolyesters with various compositions were synthesized through a direct polycondensation reaction with titanium tetraisopropoxide as the catalyst. The results of intrinsic viscosity and GPC have proven successful in preparing high molecular weight polyesters. The compositions and the sequence distributions of the copolyesters were determined by analyses of 1H NMR and 13C NMR spectra. The sequence distributions of ethylene succinate units and trimethylene succinate (TS) units were found to be random. Their thermal properties were characterized using differential scanning calorimeter and thermal gravimetric analyzer. All of the copolymers exhibit a single glass transition temperature (Tg). There is no significant difference in the thermal stability among these polyesters. Wide angle X-ray diffractograms (WAXD) were obtained for polyesters which can be crystallized isothermally. The results of thermal analysis and the WAXD patterns indicate that the incorporation of TS units into PES significantly inhibits the crystallization behavior of PES. Additionally, the crystal pattern of PTS is quite different from that of PES. Dynamic mechanical properties of moldable polyesters were investigated using a Rheometer operated at 1 Hz. Below Tg, the incorporation of TS units into PES results in the decline of storage modulus. Above Tg, the effect of crystallinity on the storage modulus can be found. 相似文献
106.
107.
The synthesis and characterization of [Dy4(dhampH3)4(NO3)2](NO3)2 (1), a new tetranuclear dysprosium (III) complex, is described. The compound was characterized by its X-ray structure, magnetic properties as well as the luminescent spectra. The compound crystallizes in a P1? space group with a zig-zag linear form of geometry. The ac magnetic susceptibilities of the molecule indicate that it is a magnetic molecule with a slow magnetization relaxation. The molecule also exhibits an emission spectrum that was confirmed to be ligand based. These results indicate that this molecule has both a slow magnetization relaxation (that could be potentially a SMM) and luminescent properties. 相似文献
108.
Hou-Jen Tsai Shyi-Chen Wu 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):191-204
Abstract Treatment of ethyl oxalyl chloride or methyl oxalyl chloride with lithium diisopropyl(carboethoxyfluoromethyl)phosphonate[(i-PrO)2P(O)CFCO2Et]?Li+ 2 followed by in siru nucle-ophilic addition with methylmagnesium iodide or vinyl magnesium bromide affords with exclusive E-stereoselectivity formation of diethyl-2-fluoro-3-methyl fumarate (CH3)(C02Et)C[dbnd]CFCO2Et 4 or 75% of the E-isomer of a-fluoro-P-vinyl-a,P-unsaturated diester (E,Z)-(CH2[dbnd]CH)(CO2C2H5)C[dbnd]CFCO2Et 5, respectively. However, direct reaction of ethyl pyruvate with 2 gives the fluoro-olefin (CH3)(CO2Et)C[dbnd]CFCO2Et 4 with 79% E-stere-oselectivity. The E/Zratio of (CH2[dbnd]CH)(CO2Et)C[dbnd]CFCO2Et 5 depends on the HMFT or DMPU cosolvents present in the reaction mixture. 相似文献
109.
C. L. Kuo T. L. Tsai A. C. Chiang K. S. Chang-Liao J. H. Chao 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(1):465-473
The purpose of this study is to develop a neutron activation method to determine trace amounts of 129I in cement-solidified radwastes. The radwaste samples were alkaline fused using KOH and then 129I and iodine carrier were chemically separated by solvent extraction before and after neutron irradiation. Both stable iodine (127I) and 129I can be activated by neutrons through 127I (n, 2n) 126I and 129I (n, γ) 130I reactions; their activated radionuclides were counted together with a high-purity germanium detector. The chemical recovery yields ranged from 30 to 60 %, and it was found that more than 99.9 % of interfering radionuclides can be removed using solvent extraction after neutron irradiation. The minimum detectable amounts can be lowered to less than 1 mBq g?1, which is superior to low energy γ-ray spectrometry by a factor of >102, on average. The established technique can be applied to re-evaluation of 129I content in radwastes that can be re-classified to lower classes, and the cost for designing a final disposal facility can be significantly reduced. 相似文献
110.
Two fused-ring structures, 6-decyloxy-2-naphthoic acid C10ONA (3) and 6-dodecyloxyisoquinoline IS (8), were synthesized and utilized as proton donor and acceptor moieties to construct a series of simple mesogenic supramolecules. The other complementary hydrogen-bonded (H-bonded) moieties are benzoic acids, thiophenecarboxylic acid and pyridines containing different alkyl chain lengths connected by ether and ester linkages, i.e. 4-alkoxybenzoic acid C n OBA (1), terephthalic acid monoalkyl ester C n COOBA (2), 2,5-thiophenedicarboxylic acid monodecyl ester C10COOTHA (4), 4-alkoxypyridine C n OP (6) and isonicotinic acid alkyl ester C n COOP (7). Several series of simple mesogenic supramolecular dimers were constructed from 1:1 molar ratios of proton donors (C n OBA, C n COOBA, C10ONA and C10COOTHA) and proton acceptors (IS, C n OP and C n COOP), though the proton acceptor C n COOP induced phase separation in all complexes. In order to investigate their fused-ring and linking group effects on the mesogenic properties of the H-bonded complexes, analogous simple supramolecular structures are compared. Supramolecular architecture and the distinct mesomorphism of these simple H-bonded liquid crystalline materials were confirmed by polarizing optical microscopy, DSC and powder X-ray diffraction experiments. 相似文献