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61.
Side chain bromination of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) was carried out by using N-bromosuccinimide followed by phosphorylation of the bromo derivative with triethyl phosphite. Optimum conditions for minimum gel formation have been established. The products have been characterized by 'H-NMR and IR studies. Thermal behavior was investigated by thermogravimetry and differential scanning calorimetry in an air nitrogen atmosphere. Phosphorylated PPO starts to lose weight at 200°C, but the char yield increases with an increase in the phosphorus content of the polymer. 相似文献
62.
Mechanical properties of copolymers of 2-hydroxyethyl methacrylate with methyl methacrylate, ethyl methacrylate, and n-butyl methacrylate have been investigated using an Instron tensile tester. It was observed that the overall mechanical properties decrease as the ester alkyl group of alkyl methacrylate becomes bulkier. Biocompatibility of the copolymers was also investigated by implanting them subcutaneously in rats. 相似文献
63.
Polybenzimidazoles were prepared in poly(phosphoric acid) from isophthalic acid (I), terephthalic acid (T), and 3,3′-di-aminobenzidine tetrahydrochloride dihydrate (DAB). Homo-polymers of I, T, and various IT copolymers have been prepared. The polymers were characterized by viscosity, IR spectra, and nitrogen estimation. The effect of copolymer composition on UV and visible spectra, solubility in various solvents, and density was also investigated. The relative thermal stability of the polymers was evaluated by TGA and DTA. 相似文献
64.
Bimlesh Lochab Indra K. Varma Jayashree Bijwe 《Journal of Thermal Analysis and Calorimetry》2013,111(2):1357-1364
This article describes synthesis, characterization and properties of blends of benzoxazine (Bz) monomers, i.e., m-alkylphenyl-3,4-dihydro-2H-benzoxazine (Bz-C), 6,6′-(propane-2,2-diyl)bis(3-phenyl-3,4-dihydro-2H-benzoxazine (Bz-A) and 3-phenyl-3,4-dihydro-2H-benzoxazine-p-carboxylic acid (Bz-pA). Binary blends of Bz-C with Bz-pA, and Bz-A with Bz-pA were prepared by first synthesizing Bz-C or Bz-A followed by the addition of all the ingredients of Bz-pA. In a similar manner, ternary blends of Bz-C, Bz-A and Bz-pA were prepared by first synthesizing Bz-C and subsequent addition of all the ingredients of Bz-A and Bz-pA in one pot. The Bz monomer blends were characterized by 1H-NMR, FTIR spectroscopy, and differential scanning calorimetry. The temperature of onset of curing (T o), due to ring-opening polymerization of Bz was found to decrease significantly by incorporation of carboxyl groups (Bz-pA) showing thereby the catalytic effect of acid functionality. Bz polymers showed good thermal stability and incorporation of Bz-pA in blends resulted in a highly cross-linked network. The interlaminar shear strength of glass fabric reinforced composites and the lap shear strength of metal–metal joints using these resin blends was also investigated. 相似文献
65.
66.
Gopal Jeya Ravikumar Dhanalakshmi Murugan Anbarasu Viswanathan Vinitha Vajiravelu Sivamurugan 《印度化学会志》2022,99(1):100291
Chemical recycling of plastic wastes is top among the effective management of the solid wastes. Particularly the post-consumer polyethylene terephthalate (PET) plastic wastes mainly generated from the disposal of beverage bottles and placed third most produced polymeric waste. However, PET wastes could be chemically recycled using several types of homo-/heterogeneous acid or base catalysts, and an effective recycling process has yet to be achieved. Therefore, the present short review is intended to display recent reports on the depolymerization of PET polymer wastes. The review aimed to cover glycolysis and aminolytic depolymerization using various catalytic systems. There is a wide spectrum of catalytic systems such as metal oxides, ionic liquids, organic bases, nanoparticles, porous materials and microwave-assisted rapid depolymerization methods have been developed toward the yield enhancement of the depolymerized products. Ideologically, the present review would benefit the researchers in familiarizing themselves with the latest developments in this field. 相似文献
67.
Relaxation dynamics of plasmons in Au−SiO2 core-shell nanoparticles have been followed by femtosecond pump-probe technique. The effect of excitation pump energy and surrounding medium on the time constants associated with the hot electron relaxation has been elucidated. A gradual increase in the electron-phonon relaxation time with pump energy is observed and can be attributed to the higher perturbation of the electron distribution in AuNPs at higher pump energy. Variation in time constants for the electron-phonon relaxation in different solvents is rationalized on the basis of their thermal conductivities, which govern the rate of dissipation of heat of photoexcited electrons in the nanoparticles. On the other hand, phonon-phonon relaxation is found to be much less effective than electron-phonon relaxation for the dissipation of energy of the excited electron and the time constants associated with it remain unaffected by thermal conductivity of the solvent. 相似文献
68.
Layer BD York A Antonsen TM Varma S Chen YH Leng Y Milchberg HM 《Physical review letters》2007,99(3):035001
We report the development of corrugated "slow-wave" plasma guiding structures with application to quasiphase-matched direct laser acceleration of charged particles and generation of a wide spectrum of electromagnetic radiation. These structures support guided propagation at intensities up to 2 x 10(17) W/cm(2), limited by our current laser energy and side leakage. Hydrogen and argon plasma waveguides up to 1.5 cm in length with corrugation period as short as 35 microm are generated in a cryogenic cluster jet. Experimental data are consistent with simulations showing periodic modulations of the laser pulse intensity. 相似文献
69.
Archana Chaudhary Ram Gopal Meena Nagar Rakesh Bohra 《Journal of Sol-Gel Science and Technology》2014,69(1):102-106
Some oxime modified complexes of the type [Zr{OPri}4?n{L}n] {where, n = 1–4 and LH=(CH3)2C=NOH (1–4) and C9H16C=NOH (5–8)} have been synthesized by the reaction of [Zr(OPri)4·PriOH] with oximes, in anhydrous refluxing benzene. These synthesized complexes were characterized by elemental analyses, molecular weight measurements, ESI-mass, FT-IR and NMR (1H and 13C{1H}) spectral studies. The ESI-mass spectral studies indicate dimeric nature for [Zr{OPri}2{ONC(CH3)2}2] (2), [Zr{OPri}3{ONC10H16}] (5) and [Zr{OPri}{ONC10H16}3] (7) and monomeric nature for [Zr{ONC10H16}4] (8). Oximato ligands appear to bind the zirconium in side on manner in all the complexes. Thermogravimetric curves of (2) and (8) exhibit multi-step decomposition with the formation of ZrO2, under nitrogen atmosphere. Sol–gel transformations of precursors (5), (6), (7) and (8) in organic medium, yielded nano-sized tetragonal phase of zirconia samples (a), (b), (c) and (d), respectively, on sintering at ~600 °C. All these samples were characterized by Powder XRD patterns and EDX analyses. Surface morphologies of these samples were investigated by SEM images. 相似文献
70.
Jiabin Zhang Ding Liu Varma Saikam Madhusudhan R. Gadi Christopher Gibbons Xuan Fu Heliang Song Jin Yu Shukkoor M. Kondengaden Prof. Dr. Peng G. Wang Prof. Dr. Liuqing Wen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(45):19997-20001
Historically, researchers have put considerable effort into developing automation systems to prepare natural biopolymers such as peptides and oligonucleotides. The availability of such mature systems has significantly advanced the development of natural science. Over the past twenty years, breakthroughs in automated synthesis of oligosaccharides have also been achieved. A machine-driven platform for glycopeptide synthesis by a reconstructed peptide synthesizer is described. The designed platform is based on the use of an amine-functionalized silica resin to facilitate the chemical synthesis of peptides in organic solvent as well as the enzymatic synthesis of glycan epitopes in the aqueous phase in a single reaction vessel. Both syntheses were performed by a peptide synthesizer in a semiautomated manner. 相似文献