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101.
Ravi Mosurkal Lynne A. Samuelson Arti Tewari Arthur C. Watterson Virinder S. Parmar Jayant Kumar 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(12):1228-1232
Aromatic dianhydrides have been identified as potential candidates for crosslinking with biocatalytically synthesized siloxane copolymers containing a functional amino group on the isophthalate moieties. We present the synthesis, characterization, thermal and flame retardant properties of this novel class of crosslinked organo-siloxane copolymers. We also discuss the effect of the concentration of one of the crosslinkers, 1,2,4,5-benzenetetracarboxylic dianhydride (DAH), on thermal decomposition and flame retardant properties using thermogravimetric analysis (TGA) and pyrolysis combustion flow calorimetry (PCFC) studies. The char yields were improved in all the polymers crosslinked with the various aromatic dianhydrides. The heat release capacity of a polymer crosslinked with 20% DAH, compared to the pure polymer, was tremendously reduced from 190 J/gK to 100 J/gK. The decomposition kinetics from TGA showed that the crosslinked polymer is thermally more stable than the non-crosslinked polymer. 相似文献
102.
Subhalakshmi Nagarajan Ramaswamy Nagarajan Rahul Tyagi Jayant Kumar Ferdinando F. Bruno Lynne A. Samuelson 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(11):951-956
Hematin, a hydroxyferriprotoporphyrin, is the stable, oxidized form of heme. Heme has been reported to be the active catalytic center of naturally occurring peroxidases such as horseradish peroxidase (HRP). While there have been reports on the use of hematin as a catalyst for oxidative polymerization reactions, these reactions could be carried out only at high pH conditions due to limited aqueous solubility of hematin at lower pH conditions. We report here the biocatalytic modification of hematin using a lipase, Novozyme-435. Hematin has been modified by tethering monomethoxy polyethylene glycol (mPEG) chains which provide aqueous solubility over a fairly wide range of pH conditions. This pegylated Hematin (PEG-Hematin) is synthesized via a one-step solventless reaction and the products formed can be isolated with minimal purification. The PEG-Hematin synthesized serves as a robust alternative to HRP for the polymerization of aniline and phenol. 相似文献
103.
Main‐chain thermotropic liquid‐crystalline aromatic azobenzene polyesters containing rigid 4,4′‐dihydroxyazobenzene mesogens and flexible spacers with varying lengths were synthesized using a chemo‐enzymatic method. The enzyme‐catalyzed approach is based on immobilized candida antarctica lipase B. The resulting polyesters were characterized by 1H‐NMR, 13C‐NMR, differential scanning calorimetry (DSC), and polarized light optical microscopy (POM). 相似文献
104.
Ryan M. Bouldin Lucas Kyriazidis Allison Fidler Sethumadhavan Ravichandran Jayant Kumar Lynne A. Samuelson 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(12):976-982
A one-pot, environmentally friendly enzymatic method is described for the synthesis a polypyrrole derivative, poly(3-methylpyrrole) (poly(3-MP)) in an aqueous solvent system. The enzyme, soybean peroxidase (SBP), was shown to successfully polymerize the beta functionalized pyrrole monomer. The resulting polymer was semiconducting, thermally stable, and exhibited bipolaron absorptions when synthesized in the presence of poly(sodium 4-styrenesulfonate) (PSS). Polymers synthesized in the presence of 10-camphor sulfonic acid (CSA) were found to exhibit slightly higher conductivity values, but were less thermally stable compared to poly(3-MP) polymerized in the presence of PSS. This work should stimulate further interest in expanding the use of enzymes as catalysts for the polymerization of other pyrrole derivatives, as well as other classes of conjugated polymers. 相似文献
105.
106.
107.
L. E. Samuelson R. A. Emigh D. E. Prull R. E. Anderson J. J. Kraushaar R. A. Ristinen 《Zeitschrift für Physik A Hadrons and Nuclei》1980,294(4):353-370
The level scheme of106Ag has been studied using the103Rh(α,nγ)106Ag and104Pd(α,pnγ)106Ag Reactions. The experimental information is taken fromγ-ray coincidence data using Ge(Li)-Ge(Li) and HPGe-planar Ge(Li) configurations andγ-ray angular distributions. With these measurements 126 γ rays have been assigned to106Ag with 116 deexciting 78 states below 2.26 MeV in excitation. The location of the 8.4-day 6+ isomer is established at 89.63±0.09 keV. Many of the low-lying states are interpreted in terms of a slightly deformed rotor model. 相似文献
108.
S. Patel Joseph Rivlin T. Samuelson O. A. Stamm H. Zollinger 《Helvetica chimica acta》1968,51(1):169-182
(1) A method is described which allows the elucidation of the structure of cotton cross-linked with formaldehyde. It consists of a permethylation process (5 methylations with dimethyl sulphate and sodium hydroxide in dimethyl sulphoxide, followed by two exchange methylations of the formalised sodium cellulosate with methyl iodide in n-butanol), hydrolysis of the product in 72% sulphuric acid to the respective methylated glucoses, reduction of the mixture of glucoses to the respective sorbitols, blocking of all free hydroxyl groups by acetylation, trifluoroacetylation or formation of trimethylsilyl ethers, and vapour phase chromatographic separation of the derivatives. (2) It is shown that after permethylation practically no free hydroxyl groups can be detected and that scarcely any replacement of methylene or oxymethylene cross-links by methyl groups has taken place. With the exception of losses in filtration of the permethylation product, all stages of the process proceed on an almost quantitative basis. 相似文献
109.
An automatic system is described for the determination of various uronic and biouronic acids after chromatographic separation on an anion-exchange column. Elution is carried out with sodium acetate or acetic acid, and the colors developed with carbazole and after oxidation with chromic acid are determined in a multichannel photometer and recorded continuously. 相似文献
110.