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R. Mateva KR. Zhilkova G. Zamfirova R. Díaz‐Calleja A. Garcia‐Bernabé 《Journal of Polymer Science.Polymer Physics》2010,48(23):2518-2529
The molecular dynamics of new poly (ω‐dodecalactam‐co‐ε‐caprolactam‐co‐propylene oxide) copolymers (DL/CL/PAC) has been investigated by using dynamic mechanical thermal analysis (DMTA) and dielectric relaxation spectroscopy (DRS) measurements. The copolymers were synthesized via anionic polymerization of relevant lactams activated with carbamoyl derivatives of telechelic hydroxyl terminated polypropylene oxide with isophorone diisocyanate (PAC). The calorimetric, X‐ray diffraction, and DMTA measurements were performed to recognize the influence of the composition ratio and the type of PAC on the physical, thermal, and mechanical properties of the synthesized copolymers. The DRS was used to study the frequency dependence of the dielectric permittivity of some isotherms from ?110 to 145 °C. Copolymerization of ε‐caprolactam with about 10 wt % ω‐dodecalactam results in a copolymer that has lower water absorption, a melting point close to that of polyamide 6 and has a high enough degree of crystallinity in respect to high storage modulus. Five dielectric relaxations have been observed in the dielectric spectra, three at lower temperature and two at higher temperature. The copolymers have two glass transition temperatures for polyamide segments and polyether blocks, indicating microphase separation in the copolymers. Other studies directed toward molecular dynamics of polyamide DL/CL/PAC copolymers have not been reported. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010 相似文献
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Milan Klikar Parmeshwar Solanke Jiří Tydlitát Filip Bureš 《Chemical record (New York, N.Y.)》2016,16(4):1886-1905
Push–pull molecules represent a unique and fascinating class of organic π‐conjugated materials. Herein, we provide a summary of their recent extraordinary design inspired by letters of the alphabet, especially focusing on H‐, L‐, T‐, V‐, X‐, and Y‐shaped molecules. Representative structures from each class were presented and their fundamental properties and prospective applications were discussed. In particular, emphasis is given to molecules recently prepared in our laboratory with T‐, X‐, and Y‐shaped arrangements based on indan‐1,3‐dione, benzene, pyridine, pyrazine, imidazole, and triphenylamine. These push–pull molecules turned out to be very efficient charge‐transfer chromophores with tunable properties suitable for second‐order nonlinear optics, two‐photon absorption, reversible pH‐induced and photochromic switching, photocatalysis, and intercalation.
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Thiothenoyltrifluoroacetone in carbon tetrachloride-butanol (1:1) is used for extraction and spectrophotometric determination of vanadium (IV) at pH 4.5-5. The greenish-yellow complex is measured spectrophotometrically at 450 nm. The system conforms to Beer's law over the range 2-11 mug/ml of extract. The colour of the complex is stable for at least 80 hr. Vanadium (IV) was quantitatively extracted and determined in the presence of 120:1 w/w ratios of various ions. The method was made selective by using common sequestering agents or prior extraction with tributyl phosphate, diethylammonium diethyldithiocarbamate, alpha-furildioxime or acetylacetone. The method is rapid, simple, selective and sensitive. 相似文献
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Rajesh S. Bhosale Chandrakant V. Magar Kuldeep S. Solanke Sandeep B. Mane Sunil S. Choudhary 《合成通讯》2013,43(24):4353-4357
An iodine/DMSO system is introduced as an excellent catalyst in three‐component coupling reactions of tetrahydrobenzo[b]pyran synthesis. The reaction proceeds quickly under very mild reaction conditions. 相似文献
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Often the rate of passage of gaseous molecules through model zeolites is too small to be computed directly. An estimate for the rate of passage of CCl4 through the 8-ring window in a model of zeolite A has been obtained by combining a direct evaluation of the free energy profile and an adaptation of the rare events method. First the free energy profile is found from a direct evaluation of the canonical partition function at high dilution and the transition state theory rate constant obtained. The dynamic correction factor is then estimated from molecular dynamics runs and used to compute the actual rate keff. The method is used to estimate the rate of passage through the 8-ring window in a rigid model of zeolite A, and the results are compared with those obtained from rigid models with expanded windows and from the flexible model. Even a small expansion in the 8-ring window diameter increases the rate significantly, but the changes associated with a flexible cage are small. 相似文献
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Roshmi Thomas Aswathi P. Nair Soumya KR Jyothis Mathew Radhakrishnan EK 《Applied biochemistry and biotechnology》2014,173(2):449-460
Silver nanoparticles form promising template for designing antimicrobial agents against drug resistant pathogenic microorganisms. Thus, the development of a reliable green approach for the synthesis of nanoparticles is an important aspect of current nanotechnology research. In the present investigation, silver nanoparticles synthesized by a soil Bacillus sp. were characterized using UV–vis spectroscopy, FTIR, SEM, and EDS. The antibacterial potential of biosynthesized silver nanoparticles, standard antibiotics, and their conjugates were evaluated against multidrug-resistant biofilm-forming coagulase-negative S. epidermidis strains, S. aureus, Salmonella Typhi, Salmonella Paratyphi, and V. cholerae. Interestingly, silver nanoparticles (AgNPs) showed remarkable antibacterial activity against all the test strains with the highest activity against S. epidermidis strains 145 and 152. In addition, the highest synergistic effect of AgNPs was observed with chloramphenicol against Salmonella typhi. The results of the study clearly indicate the promising biomedical applications of biosynthesized AgNPs. 相似文献