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971.
Jun Zeng Haoqing Hou Joachim H. Wendorff Andreas Greiner 《Macromolecular rapid communications》2005,26(19):1557-1562
Summary: Poly(vinyl alcohol) (PVA) was derivatized by polymer analogous reaction with thienyl acryloyl chloride and processed to submicrometer fibers by electrospinning from aqueous solution. Water solubility of otherwise water‐soluble PVA fibers was reduced considerably by UV crosslinking of thienyl acrylate modified PVA fibers in the solid state. Water stability of these crosslinked fibers was proven by water steam test at 95 °C.
972.
973.
Francesca Toja Daniela Saviello Austin Nevin Daniela Comelli Massimo Lazzari Gianluca Valentini Lucia Toniolo 《Polymer Degradation and Stability》2013
After the systematic study of poly(vinyl acetate) degradation presented in part 1, this work reports results from the analysis of polymeric materials from five Italian design lamps from the 1960s made of the material known as cocoon. Micro- and non-destructive molecular spectroscopic techniques have been applied directly on the object surfaces using an optical fibre probe and through examination of micro-samples: the combined use of Fourier-transform infrared spectroscopy (FTIR), pyrolysis gas-chromatography/mass-spectrometry (py-GC/MS) and Fluorescence spectroscopy allowed the assessment of the material composition and the chemical modifications of the polymers related to on-going deterioration processes. Fluorescence spectroscopy proved particularly sensitive for the detection of variations in composition among lamps and between areas on the same object, and was used to classify objects in different groups using principal component analysis of excitation emission spectra. Specific degradation products have been mapped using FTIR on micro-samples. Moreover, the interpretation of the emission spectra of the studied polymeric lamps suggests that fluorescence spectroscopy can be used for non-destructive monitoring of the degradation of historical polymeric objects. 相似文献
974.
Magda A. Akl Ali A. Sarhan Kamel R. Shoueir 《Journal of Dispersion Science and Technology》2013,34(10):1399-1408
Core-shell smart ionic nanogels based on poly(vinyl alcohol) (PVA) core and poly(N-isopropylacrylamide/acrylic acid) p(NIPAm-AAc) shell particles were successfully synthesized through a one-step surfactant-free emulsion polymerization method (SFEP). Different mole ratios of p(NIPAm-AAc) shells were synthesized. The morphologies of PVA/p(NIPAm-AAc) nanogels were investigated by transmission electron microscope (TEM). The data showed the formation of spherical nanoparticles and well-defined core-shell nanogels. PVA/p(NIPAm-AAc) core-shell nanogels were applied as a novel polymeric adsorbent to remove heavy metal pollutants from aqueous solution. Copper(II) (Cu2+) ions were selected as the target pollutant to evaluate these nanoparticles’ adsorption capability. The influence of the uptake conditions such as pH, weight ratio of nanoparticles, time, initial feed concentration, and adsorption temperature on the metal ion binding capacity of nanogels was also tested. Adsorption equilibrium data were calculated according to Langmuir and Freundlich isotherms. It was found that the sorption of Cu2+ was better suited to the Freundlich adsorption model than the Langmuir adsorption model. Also, the selectivity of the nanogels toward the different metal ions such lead (Pb2+) and cadmium (Cd2+) were tested. The maximum of Cu2+ ions adsorbed on to PVA/p(NIPAm-AAc) core-shell nanogels adsorbent was 94 mg/g obtained under simple and fast experimental conditions, indicating these nanogels can be used as effective and practical polymeric adsorbents. 相似文献
975.
Ayman M. Atta Adlia A. Gaser Zaneib F. Kamel 《Journal of Dispersion Science and Technology》2013,34(11):1456-1464
Copolymers of 2-acrylamido-2-methyl propane sulfonic acid and acrylic acid were crosslinked in the presence of different mol% of either vinyl trimethoxy silane (VTMS) as the crosslinking agent under acidic conditions or N,N-methylenebisacrylamide (MBA) as crosslinker using solution radical polymerization. The resultant xerogels were characterized by extracting the soluble fractions and measuring the equilibrium water content. Soluble fractions of the crosslinked networks were reduced by varying the MBA and VTMS concentrations. The surface morphology of the crosslinked polymers was observed by scanning electron microscope. The influence of pH on the swelling behavior of gels was investigated. The swelling behaviors of the resulting gels show pH sensitivity. 相似文献
976.
David Ellis 《合成通讯》2013,43(14):2585-2595
The conversion of trichloromethyl and tribromomethyltriazoles to the corresponding carboxamide derivatives is described. The trihalomethyl analogs are straightforward to make and react readily with a range of amines to produce carboxamides. The strategy avoids the problems of decarboxylation associated with the use of triazole acids. 相似文献
977.
We report here a one step synthesis of a new series of bis‐[1,2,4‐triazolo][4,3‐a:3′,4′‐d][1,5]benzodiazepines 3a–e and [1,2,4]oxadiazolo[5,4‐d][1,2,4]triazolo[4,3‐a][1,5]benzodiazepines 5a–c by the condensation reactions of diarylnitrilimines and arylonitrile oxides. This 1,3‐dipolar cycloaddition is completely regioselective. The structure of these products has been confirmed by 1H, 13C NMR and mass spectroscopic. 相似文献
978.
979.
Jeffrey H. Byers Peter H. Goff Nicholas J. Janson Michael G. Mazzotta John E. Swigor 《合成通讯》2013,43(11):1865-1871
The phenylseleno radical–catalyzed addition of dimethyl 2‐ethynylcyclopropane‐1,1‐dicarboxylate to electron–rich olefins has been achieved. This radical process leads to formation of highly substituted ethynylcyclopentane products through a [3+2] annulation. 相似文献
980.