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排序方式: 共有117条查询结果,搜索用时 31 毫秒
41.
Lotfi Aroua 《合成通讯》2013,43(11):1935-1942
The synthesis of bis(oxazolidinone)polyoxyethylene derivatives 2a–h from oligoethylene glycols diglycidyl ethers 1a–e and isocyanates is reported. The reaction was achieved by lithium bromide and tributylphosphine oxide. These bis‐oxazolidinones may have important antibacterial activity. 相似文献
42.
Wumanjiang Eli Wenhai Chen Qunji Xue 《Journal of Dispersion Science and Technology》2013,34(6):1659-1674
A series of triblock nonionic surfactants with different Propylene oxide and ethylene oxide chain lengths were synthesized. The triblock nonionic surfactants and poly(ethylene glycols) with different molecular weight were used, to find the effects of polymer chain length and size of the micelles on the cloud point of the surfactants. Two possible models are considered on the basis of cloud point changes of the solutions, to describe the polymer- surfactant interactions. One model suggests that flocculation depletion for the polymer chains exist between two regular micelles. This provides the driving force for the neighboring micelles to approach each other and destabilize the colloidal system. The flocculation effect is more important for polymers with a shorter chain block the approach of the micelles, since there is no typical polymer-surfactant association formed but just simple small molecule associations in which the steric and solvation effects of the polymer chains make the inter-micelles interactions repulsive. The other model considers that intra-chain micelles of polysoap are formed among the surfactant monomers and long polymer chains. The bridging attraction between two intra-chain micelles in such structures can enhance the collisions among the micelles, due to the exchange of amphiphilic monomers among the neighboring micelles. 相似文献
43.
The electronic absorption spectra of charge-transfer complexes (CTC) of benzotriazole derivatives including 2(2H-hydroxyphenyl)2H-benzotriazole-containing copolymers with various electron acceptors were investigated. While no charge-transfer interaction was observed with weak acceptors, strong acceptors such as trinitrofluorenone and pyromellitic anhydride exhibited an absorption of the contact charge-transfer type with these donors. When the very strong acceptor tetracyanoethylene was used as acceptor, new peaks of a CTC type appeared at longer wavelengths. From the wavelengths of the absorption maxima and the equilibrium constants of the CTC, the electron-donating ability of several related (2(2-hydroxyphenyl)2H-benzotriazole derivatives was estimated as follows: 2(2-Hydroxy-5-methylphenyl)2H-benzotriazole > 2H-benzotriazole > 2(4-hydroxyphenyl)2H-benzotriazole > 2(2-acetoxy-5-methylphenyl)2H-benzotriazole > copolymers containing 2(2-hydroxyphenyl)2H-benzotriazole groups. 相似文献
44.
Totan Adak Jitendra Kumar N. A. Shakil S. Walia Abhishek Kumar A. C. Watterson 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(10):767-775
Twelve amphiphilic polymers were synthesized using poly(ethylene glycols) (PEGs) of different molecular weights, viz. 300, 600 and1000 as hydrophilic block and aliphatic diacids namely glutaric acid, adipic acid, pimelic acid and suberic acid as hydrophobic block in presence of catalyst Conc. H2SO4. Synthesized polyesters were characterized by using 1H-NMR, 13C-NMR and IR spectroscopy. Micellar sizes of the polymers were determined using Dynamic Light Scattering (DLS) which ranged from 127.5–354 nm. Transmission Electron Microscope (TEM) results confirm the findings of DLS. Critical Micelle Concentrations (CMC) of the synthesized polymers were determined using electrical conductivity meter which ranged from 112 to 155 mg L?1. 相似文献
45.
Summary An effective and rapid GC separation of ethanolamines, even in the presence of ethylene glycols, using short glass capillary columns is developed. No preliminary derivatisation of the sample is necessary. The separation is completed in 6 minutes. 相似文献
46.
The reaction of benzaldehyde with aliphatic glycols was performed over Al-MCM-41 with various Si/Al ratios. The effects of various parameters like temperature, mole ratio, reaction time and catalyst amount on the formation of acetals were optimized. The mesoporous Al-MCM-41 (Si/Al ratio 36, 57, 81 and 108) were synthesized by hydrothermal method. The synthesized catalysts were characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption isotherm (BET), thermo gravimetric-differential thermal analysis (TGA-DTA) and TEM techniques. The acidity of the catalysts was measured by pyridine adsorption followed by FT-IR analysis. TEM analysis showed that the honeycomb-like regular arrangement of hexagonal pores on the molecular sieves. The highly hydrophobic Al-MCM-41 (108) showed higher activity than the other Si/Al ratios. The activity of the catalysts showed the following order Al-MCM-41 (108) > Al-MCM-41 (81) > Al-MCM-41 (57) > Al-MCM-41 (36). The hydrophobicity and nucleophilicity of the glycols highly influences the conversion of benzaldehyde, it followed the order; hexylene glycol (HG) > propylene glycol (PG) > ethylene glycol (EG). The results showed that mole ratio of 1:3 (aldehyde:glycol) gave higher yield than the other mole ratios. 相似文献
47.
《Physics and Chemistry of Liquids》2012,50(4):508-518
Viscosities of the ternary mixtures containing 2-methoxyethanol (ME) or 2-ethoxyethanol (EE), sulfolane (SULF) and ethylene glycols [ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG) and tetraethylene glycol (TETRAEG)] have been measured, at T?=?303.15?K and atmospheric pressure, over the whole composition range. From these experimental data, the deviations in viscosities (Δη 123) were calculated. These quantities were fitted to the Cibulka polynomial equation to derive the ternary adjustable parameters and standard errors. The results are discussed on the basis of intermolecular interactions between the components of the analysed mixtures. 相似文献
48.
Xin-Xue Li Wei-Dong Zhou Xiao-Ya Li Jian-Ling Sun Wei Jiang 《Journal of Molecular Liquids》2009,148(2-3):73-76
Densities and viscosities have been measured as a function of composition for the binary liquid mixture of diethylene glycol monomethyl ether CH3O(CH2)2O(CH2)2OH + water at T = (293.15, 303.15, 313.15, 323.15, 333.15) K under atmospheric pressure. Densities were determined using a capillary pycnometer. Viscosities were measured with Ubbelohde capillary viscometer. From the experimental data, the excess molar volumes VE, and viscosity deviations δη, and the excess energies of activation for viscous flow ΔG*E were calculated. These data have been correlated by the Redlich–Kister type equations to obtain their coefficients and standard deviations. The results suggest that molecular interaction between diethylene glycol monomethyl ether and water is strong. 相似文献
49.
Zen Maeno Kaoru Midogochi Takato Mitsudome Tomoo Mizugaki Koichiro Jitsukawa 《Tetrahedron letters》2018,59(9):832-835
A convenient and sustainable method for the synthesis of glycol diesters was developed through the depolymerization of polyethylene glycols (PEGs) with carboxylic acids using proton-exchanged montmorillonite as an efficient solid acid catalyst. Several functionalized glycol diesters were obtained in good yields from PEGs and readily available carboxylic acids. Upon reaction completion, the catalyst could be easily separated by filtration and reused with its activity remaining unchanged. 相似文献
50.
Ken Kojio Yoshiteru Nonaka Tetsuo Masubuchi Mutsuhisa Furukawa 《Journal of Polymer Science.Polymer Physics》2004,42(24):4448-4458
Randomly copolymerized poly(carbonate) glycols were employed as starting materials for the synthesis of polyurethane elastomers (PUEs). The poly(carbonate) glycols had hexamethylene (C6) and tetramethylene (C4) units between carbonate groups in various composition ratios (C4/C6 = 0/100, 50/50, 70/30, and 90/10), and the number‐average molecular weights of these poly(carbonate) glycols were 1000 and 2000. The PUEs were synthesized with these poly(carbonate) glycols, 4,4′‐diphenylmethane diisocyanate, and 1,4‐butanediol by a prepolymer method. Differential scanning calorimetry measurements revealed that the difference between the glass‐transition temperature of the soft segment in the PUEs and the glass‐transition temperature of the original glycol polymer decreased and the melting point of the hard‐segment domain increased with an increasing C4 composition ratio. The microphase separation of the poly(carbonate) glycol‐based PUEs likely became stronger with an increasing C4 composition ratio. Young's modulus of these PUEs increased with an increasing C4 composition ratio. This was due to increases in the degree of microphase separation and stiffness of the soft segment with an increase in the C4 composition ratio. The molecular weight of poly(carbonate) glycol also influenced the microphase‐separated structure and mechanical properties of the PUEs. The addition of different methylene chain units to poly(carbonate) glycol was quite effective in controlling the microphase‐separated structure and mechanical properties of the PUEs. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4448–4458, 2004 相似文献