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991.
Muhammad Ajaz Hussain Anqa Zarish Khawar Abbas Muhammad Sher Muhammad Nawaz Tahir Wolfgang Tremel Muhammad Amin Abdul Ghafoor Bilal Ahmad Lodhi 《Cellulose (London, England)》2013,20(2):717-725
This article presents synthesis of novel macromolecular prodrugs of aceclofenac (an anti-inflammatory drug) onto hydroxypropylcellulose (HPC). The HPC-aceclofenac conjugates were prepared using an acylating agent 1,1′-carbonyldiimidazole (CDI) under homogenous reaction conditions. Aceclofenac was first activated by using CDI to form its N-acylimidazole. The N-acylimidazole of aceclofenac was then reacted with HPC polymer at 80 °C for 24 h. Highly pure prodrugs of aceclofenac were synthesized with a wide range of moderate to high degree of substitution (DS 0.41–2.12) as calculated by 1H NMR spectroscopy. The UV spectroscopic analysis has also revealed that the active drug aceclofenac was found in different conjugates from 28 to 67 mg/100 mg of HPC-aceclofenac conjugates which are in good agreement with DS calculated by 1H NMR spectroscopy. The gel permeation chromatography showed unimodal absorption that indicates no significant degradation in polymer chains during the reaction. The macromolecular prodrugs of aceclofenac were characterized using different spectroscopic and chromatographic techniques. The thermal analysis has revealed that HPC-aceclofenac conjugates (prodrugs) are 92 and 96 °C more stable than pure aceclofenac regarding their initial (Tdi) and maximum degradation temperatures (Tdm), respectively. The activation energy (Ea) and frequency factor (Z) of the degradation reactions were evaluated using Friedman, Broido and Chang methods. Degradation followed first order (n) kinetics. Transmission electron microscopy has revealed the formation of sponge like nano aggregates with population size distribution of around 80–150 nm. 相似文献
992.
M. Ijaz Khan Tasawar Hayat Sumaira Qayyum Muhammad Imran Khan A. Alsaedi 《Physics letters. A》2018,382(34):2343-2353
Here a novel applications of entropy generation optimization is presented for nonlinear Sisko nanomaterial flow by rotating stretchable disk. Flow is examined in the absence of magnetohydrodynamics and Joule heating. Total irreversibility rate (entropy generation rate) is investigated for different flow parameters. Heat source/sink and viscous dissipation effects are considered. Impacts of Brownian motion and thermophoresis on irreversibility have been analyzed. Governing flow equations comprise momentum, energy and nanoparticle concentration. Von Karman's similarity variables are implemented for reduction of PDEs into ODEs. Homotopy analysis technique for series solutions is implemented. Attention is given to the irreversibility. The impacts of different flow parameters on velocity, nanoparticle concentration, temperature and irreversibility rate are graphically presented. From obtained results it is examined that irreversibility rate enhances for larger estimation of Brinkman number and diffusion. Furthermore it is also examined that temperature and nanoparticle concentration show contrast behavior through Prandtl number and Brownian motion. 相似文献
993.
Latif Ullah Guoying Zhao Zichen Xu Hongyan He Muhammad Usman Suojiang Zhang 《中国科学:化学(英文版)》2018,61(4):402-411
Heteropoly acids(HPA) are well known for their versatile solid acid catalysis in diverse chemical reactions, however they suffer from low surface area(10 m~2/g) and leaching into the reactions media, which reduce their prospects as industrial catalyst.Herein, a novel hybrid material HPW@Zr-BTC,composed of 12-tungstophoric acid(HPW) and Zr~(Ⅳ)-benzene tri-carboxylate(Zr-BTC) metal-organic framework(MOF), was prepared via one-pot solvothermal method. Excellent HPW loading up to 32.3 wt% was achieved, and HPW@Zr-BTC composite proved to be highly stable, besides the crystalline morphology of Zr-BTC was intact. The catalytic activity of the hybrid composite was explored via Friedel-Crafts acylation of anisole with benzoyl chloride.The 28.2 wt% HPW@Zr-BTC showed excellent catalytic performance, with 99.4% anisole conversion and 97.6% yield(pmethoxybenzophenone) under solvent free conditions. Excellent retention of catalytic activity was achieved after at least five consecutive runs due to non-observable HPW leaching. The promising activity and stability of the catalyst forecasted its potential industrial applications. 相似文献
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995.
Raza M. A. Amin M. Muhammad G. Rashid A. Adnan A. 《Russian Journal of General Chemistry》2017,87(11):2678-2683
Russian Journal of General Chemistry - Herein we present the study of synthesis of novel bio-organometallic conjugates using 1,3-dipolar cycloaddition click reactions. Amino acid azides such as... 相似文献
996.
Aqib Zahoor Afsar Khan Viqar U. Ahmad Amir Ahmed Saleha S. Khan Muhammad I. Ali 《Helvetica chimica acta》2012,95(9):1613-1622
The AcOEt‐soluble part of a MeOH extract from the whole plant of Erigeron bonariensis yielded two new rare‐class octulosonic acid derivatives, rel‐methyl (1R,2S,3S,5R)‐3‐(trans‐caffeoyloxy)‐7‐[(trans‐caffeoyloxy)methyl]‐2‐hydroxy‐6,8‐dioxabicyclo[3.2.1]octane‐5‐carboxylate ( 1 ) and 5,8‐di[O‐trans‐caffeoyl]‐3‐deoxy‐β‐D ‐gluco‐oct‐2‐ulopyranosonosyl 4,8‐di[O‐trans‐caffeoyl]‐3‐deoxy‐β‐D ‐gluco‐oct‐2‐ulopyranosidonic acid ( 2 ) along with a cyclohexanecarboxylic acid derivative, (1α,3β,4β,5β)‐1,4‐di‐3,5‐dihydroxy‐bis(trans‐caffeoyloxy)cyclohexanecarboxylic acid ( 3 ). The structures of these compounds were elucidated through ESI‐MS, and 1D‐ and 2D‐NMR spectroscopic techniques including 1H‐ and 13C‐NMR, HMQC or HSQC, and HMBC experiments. 相似文献
997.
An efficient approach was employed to simultaneously functionalize and reduce the graphene oxide (GO) with p-phenylene diamine (PPD) using simple refluxing. There was a possibility of nucleophilic substitution of amino moieties of PPD with the epoxy groups of GO. The polythiophene (PTh) and polythiophene-co-poly(methylmethacrylate) (PTh-co-PMMA) nanocomposites with chemically modified GO were prepared using in situ polymerization technique. Two series of nanocomposites that is PTh/PPD-GO and PTh-co-PMMA/PPD-GO were designed. The nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, scanning electron microscopy (SEM), thermal conductivity, and electrical conductivity measurement. The FTIR spectra depicted the characteristic absorption peaks for the formation of copolymer and their composites with PPD-GO. The SEM micrographs showed that the PPD-GO nanosheets were homogeneously dispersed in copolymer matrix forming nano-granular morphology. The nanofluids were prepared by suspending modified GO particles inside the basefluid of polythiophene and PTh-co-PMMA. The thermal conductivity of nanocomposites was significantly improved even with low PPD-GO loading. The thermal conductivity of PTh-co-PMMA/PPD-GO with 1.5 wt.% filler was increased to 1.42 W/mK at a higher temperature. The XRD patterns confirmed the presence of chemical interactions between the copolymer and filler particles. The electrical conductivity of PTh-co-PMMA/PPD-GO was also found to increase in the range of 6.1 × 10?3–2.5 × 10?2 S/cm. Novel PTh-co-PMMA/PPD-GO-based nanocomposite is potentially significant in high-performance thermal systems. 相似文献
998.
999.
1000.
Muhammad Ali Dominik H. Hasenhrl Lukas Zeininger Alexander R. M. Müllner Herwig Peterlik Andreas Hirsch 《Helvetica chimica acta》2019,102(4)
A new prototype of reversible self‐assembly between functionalized gold and titanium dioxide nanoparticles (NPs) utilizing hydrogen bonding interactions was developed and established. The gold nanoparticles were functionalized with a Hamilton‐receptor functionality bearing a thiol moiety as anchoring group. The titanium dioxide nanoparticles were modified with cyanurate derivatives which contained phosphonic acids as anchoring groups. The host–guest type interaction between two functionalized nanoparticles yielded a highly integrated nanoparticle system in chloroform. Moreover, by presenting a competing ligand in an exchange reaction, the product of self‐assembly can be segregated into the individual soluble components of functionalized nanoparticles. The self‐assembly and the exchange reaction were followed and monitored in detail by UV/Vis spectroscopy. The structure of the self‐assembly product was investigated using scanning electron microscopy (SEM) and small‐angle X‐ray scattering (SAXS). 相似文献