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131.
Study of the polymer concentration and polymer/crosslinker ratio effect on gelation time of a novel grafted polymer gel for water shutoff using a central composite design method
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In this research article, a hydrogel was prepared by crosslinking of carboxymethyl cellulose‐g‐polyacrylamide copolymer aqueous solution with chromium(III) acetate for the purpose of a water shutoff job in the oil reservoir. The experiments were conducted to investigate the main effects of copolymer concentration and crosslinker/copolymer ratio on gelation time of the hydrogel system. Then the effects of these two factors and their interactions on the gelation time were determined by using a central composite design (CCD) of the response surface method. CCD was used to generate the quadratic mathematical model for the gelation time response as a function of copolymer concentration, crosslinker/copolymer ratio, and their interaction. Furthermore, the analysis of variance (ANOVA) was used to evaluate the quality of the quadratic model. The ANOVA result of the developed model showed that the model was highly significant. The result also showed that the crosslinker/polymer ratio had more effects on the gelation time than did the polymer concentration and their interaction. A response surface method provides an optimum gel formulation. Core flooding experiments reveal that a significant permeability reduction on the sand pack cores can be achieved at reservoir conditions, when it is treated with an optimum gel formulation. Hence, this gel system may be suitable in the water shutoff job required for enhanced oil recovery from the oil fields. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
132.
The authors study how the simultaneous presence of short-range secondary and long-range tertiary interactions controls the folding and collapse behavior of a helical macromolecule. The secondary interactions stabilize the helical conformation of the chain, while the tertiary interactions govern its overall three-dimensional shape. The authors have carried out Monte Carlo simulations to study the effect of chain length on the folding and collapse behavior of the chain. They have calculated state diagrams for four chain lengths and found that the physics is very rich with a plethora of stable conformational states. In addition to the helix-coil and coil-globule transitions, their model describes the coupling between them which takes place at low temperatures. Under these conditions, their model predicts a cascade of continuous, conformational transitions between states with an increase in the strength of the tertiary interactions. During each transition the chain shrinks, i.e., collapses, in a rapid and specific manner. In addition, the number of the transitions increases with increasing chain length. They have also found that the low-temperature regions of the state diagram between the transition lines cannot be associated with specific structures of the chain, but rather, with ensembles of various configurations of the chain with similar characteristics. Based on these results the authors propose a mechanism for the folding and collapse of helical macromolecules which is further supported by the analysis of configurational, configurational, and thermodynamic properties of the chain. 相似文献
133.
Structural Chemistry - Thirteen tetranitro-diazinodiazines have been designed and investigated to find the importance of diazinodiazine fused-heterocyclic backbone for energetic materials. The... 相似文献
134.
Dogamanti Ashok Chiranjeevi Pamula Aamate Vikas Kumar Vagolu Siva Krishna Sriram Dharmarajan Balasubramanian Sridhar Sarasija Madderla 《Molecular diversity》2021,25(4):2137-2148
Molecular Diversity - As part of an ongoing effort to develop new anti-tubercular agents, a series of novel indole-fused spirochromene hybrids (7a–l) were efficiently synthesized in excellent... 相似文献
135.
A facile and environmental friendly protocol for the synthesis of N-bridged fused bicyclic compounds such as imidazo[1,2-a]pyridines, imidazo[1,2-a]pyrimidines, and imidazo[2,1-b]thiazole, from commercially available starting materials has been developed. The reaction proceeds via NBS mediated in situ formation of α-brominated intermediate of corresponding aromatic ketones, 1,3-diketones, β-keto esters, followed by trapping with suitable nucleophiles to provide these versatile imidazole fused bicyclic heterocycles in good yields under metal-free conditions. 相似文献
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Dr. Libo Sun Dr. Zhenfeng Huang Vikas Reddu Prof. Tan Su Prof. Adrian C. Fisher Prof. Xin Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(39):17252-17257
Metal complexes have been widely investigated as promising electrocatalysts for CO2 reduction. Most of the current research efforts focus mainly on ligands based on pyrrole subunits, and the reported activities are still far from satisfactory. A novel planar and conjugated N4-macrocyclic cobalt complex (Co(II)CPY) derived from phenanthroline subunits is prepared herein, and it delivers high activity for heterogeneous CO2 electrocatalysis to CO in aqueous media, and outperforms most of the metal complexes reported so far. At a molar loading of 5.93×10−8 mol cm−2, it exhibits a Faradaic efficiency of 96 % and a turnover frequency of 9.59 s−1 towards CO at −0.70 V vs. RHE. The unraveling of electronic structural features suggests that a synergistic effect between the ligand and cobalt in Co(II)CPY plays a critical role in boosting its activity. As a result, the free energy difference for the formation of *COOH is lower than that with cobalt porphyrin, thus leading to enhanced CO production. 相似文献
139.
Abhishek Kumar Yadav Manojkumar Jujam Vikas D. Ghule Srinivas Dharavath 《Journal of heterocyclic chemistry》2024,61(3):401-406
A series of five and six-membered C-C bonded energetic materials ( 2 – 7 ) based on a combination of imidazole-triazine and triazole-triazine backbones were designed, synthesized, and characterized using NMR, IR, Mass spectrometry, and TGA-DSC studies. Further, the structure of compound 4 was supported by single-crystal X-ray analysis. All the newly synthesized energetic compounds exhibit good density, excellent thermal stability, good detonation performance, and low mechanical sensitivity toward impact and friction. Among all, the nitrate salt 4 exhibits balanced properties, including high density (1.80 g cm−3), excellent thermal stability (254°C), good detonation velocity (8178 m s−1), and low sensitivity towards impact and friction. The facile synthetic feasibility, thermal stability, energetic performance, and insensitivity of all the molecules suggest they can be used as an insensitive secondary explosive in various defense and civilian applications. 相似文献
140.
Vikas Mittal 《哲学杂志》2013,93(36):4518-4535
Different aluminosilicates, such as montmorillonite, vermiculite and mica, were surface-treated with a variety of organic modifiers to quantify factors affecting the thermal stability of the modified fillers. Montmorillonites with different cation exchange capacities were also used. Thermal characterisation was carried out via high resolution thermogravimetric analysis and the results were correlated with X-ray diffraction measurements. Modified substrates, such as montmorillonite, vermiculite and mica, differed in their thermal behaviour even when modified with the same surface modifiers. Phosphonium-based modifiers were the most thermally stable, compared to pyridinium and ammonium ions. Mixed brushes from the modifiers also influenced the thermal behaviour of the modified substrates. When further modified using physical adsorption or chemical reactions on the surface, the modified minerals also displayed alterations in the thermal behaviour of the fillers. The results can be used as a guide for the selection of surface modifiers in the nanocomposite synthesis process where compounding of the filler with the polymer at high temperature and shear is required. 相似文献