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1.
《Mendeleev Communications》2022,32(4):507-509
We report on the synthesis of new Ru(bpy)2(phen) catalyst for the oscillatory Belousov–Zhabotinsky chemical reaction and on the preparation of novel Ru(bpy)2(phen)-based self-oscillating gels. The synthesized gels exhibit high-amplitude autonomous mechanical oscillations when the Belousov–Zhabotinsky reaction proceeds inside these gels 相似文献
2.
Self‐Assembly and Gelation of Poly(aryl ether) Dendrons Containing Hydrazide Units: Factors Controlling the Formation of Helical Structures 下载免费PDF全文
Partha Malakar Prof. Dr. Edamana Prasad 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(13):5093-5100
Self‐assembly of AB2 and AB3 type low molecular weight poly(aryl ether) dendrons that contain hydrazide units were used to investigate mechanistic aspects of helical structure formation during self‐assembly. The results suggest that there are three important aspects that control helical structure formation in such systems with acyl hydrazide/hydrazone linkage: i) J‐type aggregation, ii) the hydrogen‐bond donor/acceptor ability of the solvent, and iii) the dielectric constant of the solvent. The monomer units self‐assemble to form dimer structures through hydrogen‐bonding and further assembly of the hydrogen‐bonded dimers leads to macroscopic chirality in the present case. Dimer formation was confirmed by NMR spectroscopy and by mass spectrometry. The self‐assembly in the system was driven by hydrogen‐bonding and π–π stacking interactions. The morphology of the aggregates formed was examined by scanning electron microscopy, and the analysis suggests that aprotic solvent systems facilitate helical fibre formation, whereas introduction of protic solvents results in the formation of flat ribbons. This detailed mechanistic study suggests that the self‐assembly follows a nucleation–elongation model to form helical structures, rather than the isodesmic model. 相似文献
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Jie Da Thieo E. Hogen‐Esch 《Journal of polymer science. Part A, Polymer chemistry》2004,42(2):360-373
The synthesis is reported of copolymers of N,N‐dimethylacrylamide (DMA) and methacrylates containing 2,2′‐dihydroperfluorodecanoyl (RF) groups separated from the methacrylate by long polyethylene glycol (PEG) tether groups (between 1000 and 14,000 Da). At concentrations of between 1 and 8 wt % the copolymers with macromonomer contents of 1 mol % or less give gels in organic solvents such as dioxane, THF, or methanol, as well as in water. Given the low molecular weights, this indicates very efficient association of very low numbers of RF groups. Association and gel formation is enormously enhanced in the presence of longer PEG tethers. This is consistent with smaller poly(N,N,‐dimethylacrylamide) (PDMA) intermolecular excluded volume effects that are mediated by the longer PEG tethers and possibly by the incompatibility of PEG and PDMA that may lead to the formation of PEG microdomains. This increases the local concentrations of the RF groups in the PEO domains that are not diluted by the PDMA chains, as would be the case in the absence of PEG tethers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 360–373, 2004 相似文献
5.
Shu‐Ling Huang Wei‐Kuo Chin W. P. Yang 《Journal of Polymer Science.Polymer Physics》2004,42(18):3476-3486
The tetramethoxysilane (TMOS)/2‐hydroxylethyl methacrylate (HEMA) hybrid gels were synthesized with acid and base catalysts, via the in situ polymerization of HEMA, with and without the cosolvent methanol. With methanol in the TMOS/HEMA sol, the enhanced esterification and depolymerization reactions of the silanols resulted in a slower growth of silica particles. The silica particles that were synthesized with an acid catalyst were less than 40 nm. The thermal resistance of the poly(2‐hydroxyethyl methacrylate) (PHEMA) chains was enhanced by the addition of colloidal silica. The Fourier transform infrared characterizations and the exothermal peaks on the differential scanning calorimetry traces of these hybrid gels indicated chemical hybridization occurring as a result of condensation of the colloid silica and PHEMA at higher temperatures. Hence, the residual weight content of the hybrid gel after its synthesis with the base catalyst was even higher than the content of TMOS in the hybrid sol. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3476–3486, 2004 相似文献
6.
J. Saunier F. Alloin J. Y. Sanchez B. Barrire 《Journal of Polymer Science.Polymer Physics》2004,42(3):544-552
Some microporous poly(vinylidene fluoride) (PVdF) separators for lithium‐ion batteries, used in liquid organic electrolytes based on a mixture of carbonate solvents and lithium salt LiPF6, were characterized by the study of the swelling phenomena on dense PVdF membranes. Various aspects of the kinetics of the carbonate solvents and the solvent mixture sorption in dense PVdF slabs were studied at different temperatures. Non‐Fickian behavior, characterized by S‐shaped sorption curves, was highlighted, and a salt effect, which resulted in two‐stage sorption, was studied. Diffusion coefficients and activation energies were calculated for the Fickian portions of the sorption curves, that is, at short times and low swelling ratios. A strong influence of the different interaction parameters was shown for the swelling kinetics. This study proved that the swelling of microporous PVdF membranes could be considered instantaneous. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 544–552, 2004 相似文献
7.
J. Saunier F. Alloin J. Y. Sanchez L. Maniguet 《Journal of Polymer Science.Polymer Physics》2004,42(12):2308-2317
Microporous poly(vinylidene fluoride) (PVdF) separators for lithium-ion batteries, used in liquid organic electrolytes, have been characterized with respect to the swelling phenomena on dense PVdF membranes (obtained through hot pressing). In the first and second parts of this study, we have described the swelling equilibria and swelling kinetics of dense PVdF. Here the thermal properties of PVdF gels and their irreversible modifications induced by swelling are characterized. Particular attention is paid to crystallinity modifications, polymer plasticization, and membrane degradation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2308–2317, 2004 相似文献
8.
Bakul C. Dave Xiankui Hu Yogeeswari Devaraj Shirshak K. Dhali 《Journal of Sol-Gel Science and Technology》2004,32(1-3):143-147
There is a current need for alternative coatings that can provide corrosion resistance to metals or alloy surfaces due to the environmental hazards posed by conventional coatings. Herein, we report on novel organically-modified sol–gel coatings for the protection of metal and alloy surfaces. The basic concept of chemical conversion of metal surfaces is based on deposition of a hydrophobic, nonporous sol–gel barrier layer for surface protection and corrosion prevention. The properties of these organosilica coatings can be tuned by varying the composition of precursors. The evaluation of hydrophobicity, adhesive strength, and anticorrosion properties of organically-modified sol–gel derived coatings suggests their potential utility as technologically-compatible alternatives to conventional coatings. 相似文献
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10.
T. Peprnicek A. Kalendova J. Simonik J.F. Gerard 《Polymer Degradation and Stability》2006,91(12):3322-3329
The paper concentrates on poly(vinyl chloride) - PVC - from the point of nanocomposite characterisation through thermal degradation of samples, evolution of the changes caused by elevating temperature using TGA, FTIR and Congo Red methods combined with morphological characterisation by XRD and TEM analyses. A novel method of PVC-paste/nanocomposite preparation while processing was used. During preparation, PVC plasticizer was mixed with clay, both natural and organophilic, and the suspension was then compounded with the other components. Two factors were followed: effect of shearing alone, and in combination with temperature. As is presented, the type of nano-filler and its chemical modifier have obvious influence on final properties either thermal or morphological. Presented contribution follows previous part of investigation and brings further information from PVC-paste/nanocomposite field. 相似文献