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21.
Iron polymethacrylate was synthesized by free radical solution polymerization of methacrylic acid, followed by replacement of the carboxylic proton with iron. Thermal volatilization analysis and thermogravimetry were used to study its thermal stability from ambient temperature up to 500oC. The results reveal that ferric oxide is left as residue at the end of the thermal degradation experiments.The authors dedicate this paper to the memory of the late Dr. Mohammad Zulfiqar of Quaid i Azam University, Islamabad, Pakistan. 相似文献
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23.
Ayesha Kausar Sonia Zulfiqar Liaquat Ali Muhammad Ilyas Sarwar 《Monatshefte für Chemie / Chemical Monthly》2011,17(3):201-209
Abstract
New diacid dichlorides bearing phenyl thiourea groups were prepared by a facile synthetic approach and characterized using spectroscopic and elemental analyses. A series of novel aromatic and semiaromatic polyamides were prepared via a condensation route from the synthesized diacid dichlorides with 4,4′-oxydianiline. The polymers were characterized by FT-IR, 1H NMR, 13C NMR, and their physical properties, including their solution viscosities, solubilities and thermal properties, were studied too. Polyamides with phenyl thiourea moieties in the backbone showed good solubilities in amide solvents such as DMAc, DMF, DMSO, and NMP. All of the synthesized polymers had η inh values of 0.042–0.053 dm3/g, and were obtained in quantitative yield. GPC measurements of the synthesized polyamides indicated M w values of 64,759–86,172. The crystallinity of the polymers was evaluated via their X-ray diffraction patterns. Their glass transition temperatures were found to be 218–229 °C. Furthermore, thermogravimetric analysis indicated that the polymers were thermally stable in the range 300–398 °C in a N2 atmosphere. 相似文献24.
Murtaza Hasan Ihsan Ullah Hina Zulfiqar Komal Naeem Arfa Iqbal Huma Gul Muhammad Ashfaq Nasir Mahmood 《Materials Today Chemistry》2018
Synthesis of nanomaterials is being gained extensive attention in the fields of chemistry, applied physics, catalysis, drug delivery and the most important in diagnosis and therapeutic applications. Recently, many reports have been published on physical and chemical synthesis of magnetic as well as metallic nanoparticles (NPs) with viable surface functionalization, but still there is a dire need of such strategies that can combine synthetic methodology with stable surface modification found in nature. Synthesis of NPs via biological methods is the possible way to solve these barriers. However, systematized summary and outlooks of NPs synthesis via biological entities with various influencing factors e.g. temperature, pH, concentration of reactants and reaction time has rarely been reported. This review will present the distinct advantages of biological synthesis of NPs over physical and chemical methods. It will also highlight the recent progress on synthesis of NPs via various biological systems i.e. plant, fungus, bacteria, and yeast. Furthermore, it will explain various factors that control the size, shape, and morphology of these NPs. Finally, it would present the future perspectives of green chemistry for the development of nano-science and -biotechnology. 相似文献
25.
A microwave-assisted, environmentally friendly, high-yielding, time-saving synthesis of medicinally important 3-substituted isocoumarins was carried out in a single step by direct condensation of homophthalic acid with aryol and acyl chlorides under solvent-free conditions without any solid support. The synthesised isocoumarins were structurally characterised by microanalysis, 1H NMR, EI, IR and UV. 相似文献
26.
Muhammad Ilyas Sarwar Sonia Zulfiqar Zahoor Ahmad 《Journal of Sol-Gel Science and Technology》2008,45(1):89-95
The sol–gel derived chemically combined organic–inorganic nanocomposites were synthesized from poly(etheramide) and tetraethoxysilane.
Reaction of a mixture of 4-aminophenyl ether and 1,3-phenyldiamine with terephthaloyl chloride (TPC) in dimethylacetamide
(DMAc) produced the amide chains. These chains were modified with carbonyl chloride end groups using a slight excess of diacid
chloride and were then reacted with aminophenyl trimethoxysilane (APTMOS), where the amine group reacted with carbonyl chloride
end groups. Hydrolysis/condensation of tetraethoxysilane (TEOS) and alkoxy groups present in APTMOS developed bonding between
the polyamide chains and inorganic silica network generated in situ. By changing the relative proportions of the polymer solution
and the amount of TEOS, the composition of hybrid films was varied. Thin hybrid films with various concentrations of silica
network obtained after evaporation of the solvent were subjected to mechanical, dynamic mechanical thermal and morphological
measurements. The results indicate a gradual increase in the modulus (3.84 GPa) and tensile strength (121 MPa) up to 15-wt.%
silica relative to the pure polyamide. The elongation at break point and toughness gradually decrease with addition of silica
content. These hybrids were found to be thermally stable up to a temperature of 500 °C. The weight retained above 800 °C was
roughly proportional to amount of silica in the matrix. The glass transition temperature and the storage moduli increased
with increasing silica concentration. The maximum increase in the T
g
value (358 °C) was observed with 15-wt.% silica. Scanning electron micrographs indicated the uniform distribution of silica
in the composites with an average particle size ranging from 9 to 47 nm. 相似文献
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28.
Mehwish Nawaz Haji Muhammad Shoaib Khan Naveed Akhtar Talha Jamshed Rubina Qaiser Hina Shoukat Mehrin Farooq 《Photochemistry and photobiology》2019,95(5):1243-1248
Solar radiations trigger the physiological alteration in skin which progress toward photoaging. Sunscreens are known to be effective against the photodamaging effects of sunlight. The purpose of this study was to evaluate the extent to which aging signs caused by real‐life sunlight exposure could be avoided by comparing various parameters between sun‐exposed and sun‐protected skin using noninvasive probes. Female volunteers (n = 11) after getting their consent were provided with marketed sunscreen product to apply onto their skin for 6 months. Measurements were scheduled every 15 days from the baseline reading for 6 months. Cutometer, Mexameter and Corneometer were used for evaluation of facial skin parameters. Clinical evaluations showed the effects of sunlight exposure on different skin parameters by comparing sun‐protected and unprotected skin, where Gross elasticity (R2), Net elasticity (R5), Viscoelasticity (R6) and Biological elasticity (R7) showed insignificant results, while Hydration, Melanin and Erythema showed significant results. Sun‐exposed skin presented 0.72%, 0.66%, 0.77%, 1.39%, 1.99%, 2.01% and 3.15% changes in R2, R5, R6 and R7, melanin, erythema and hydration, respectively, which were potentially prevented by sunscreen application. Premature aging is inhibited by following photoprotective regimen on routine basis, emphasizing the potential benefit of sunscreen against early aging signs. 相似文献
29.
30.
Ito T Ali Z Furusawa M Iliya I Tanaka T Nakaya K Murata J Darnaedi D Iinuma M 《Chemical & pharmaceutical bulletin》2006,54(3):363-367
Three new resveratrol oligomers, cotylelophenol C (1) (resveratrol tetramer) and cotylelosides A (2) and B (3) (O-glucosides of resveratrol trimer), together with four known glucosides of resveratrol oligomers (vaticasides A, B, C, D) and piceid, were isolated from an acetone soluble part of stem of Cotylelobium lanceolatum (Dipterocarpaceae). The structures of new compounds were determined by spectral data analysis. The characteristic properties observed in the NMR spectra of 1 were also discussed. 相似文献