共查询到20条相似文献,搜索用时 15 毫秒
1.
Naved Azum Abdullah M. Asiri Malik Abdul Rub Abdulrahman O. Al-Youbi 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2017,91(4):685-691
Thermodynamic, surface and micellar properties of anti-inflammatory drug sodium 2-(4-isobutylphenyl) propionate (sodium salt of ibuprofen (NaIBF)) in aqueous/urea solution were studied by surface tension measurements at 298.15 K in the presence of anionic surfactant sodium dodecylsulfate (SDS). Critical micelle concentration (cmc), surface tension at cmc (γcmc), maximum Gibbs surface excess (Γmax), minimum surface area per surfactant molecule at the air/water interface (A min) etc. were determined in pure water as well as in aqueous urea solution. The theories of Clint, Rosen and Rubingh have been applied to describe the interactions between these amphiphiles at the interface and in the micellar solution. Various thermodynamic parameters have been calculated and discussed in detail. 相似文献
2.
Cellulose was dissolved rapidly in 4.6 wt % LiOH/15 wt % urea aqueous solution and precooled to –10 °C to create a colorless transparent solution. 13C‐NMR spectrum proved that it is a direct solvent for cellulose rather than a derivative aqueous solution system. The result from transmission electron microscope showed a good dispersion of the cellulose molecules in the dilute solution at molecular level. Weight‐average molecular weight (Mw), root mean square radius of gyration (〈s2〉z1/2), and intrinsic viscosity ([η]) of cellulose in LiOH/urea aqueous solution were examined with laser light scattering and viscometry. The Mark–Houwink equation for cellulose in 4.6 wt % LiOH/15 wt % urea aqueous solution was established to be [η] = 3.72 × 10?2 M in the Mw region from 2.7 × 104 to 4.12 × 105. The persistence length (q), molar mass per unit contour length (ML), and characteristic ratio (C∞) of cellulose in the dilute solution were given as 6.1 nm, 358 nm?1, and 20.8, respectively. The experimental data of the molecular parameters of cellulose agreed with the Yamakawa–Fujii theory of the worm‐like chain, indicating that the LiOH/urea aqueous solution was a desirable solvent system of cellulose. The results revealed that the cellulose exists as semistiff‐chains in the LiOH/urea aqueous solution. The cellulose solution was stable during measurement and storage stage. This work provided a new colorless, easy‐to‐prepare, and nontoxic solvent system that can be used with facilities to investigate the chain conformation and molecular weight of cellulose. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3093–3101, 2006 相似文献
3.
Hydroxyethylcellulose (HEC) was synthesized by a fully homogenous method from cellulose in 7.5 wt.-% NaOH/11 wt.-% urea aqueous solutions under mild conditions. HEC samples were characterized with NMR, SEC-LLS, solubility, and viscosity measurements. The MS and DS values of the obtained HEC samples are in the range from 0.54 to 1.44 and 0.45 to 1.14, respectively, and the relative DS values at C-2 and C-6 hydroxyl groups are slightly higher than those at C-3 hydroxyl groups. HEC samples are soluble in water starting from a MS of 0.57 and DS of 0.49, which display high viscosity in aqueous solutions. Moreover, a NaOH/urea aqueous solution is a stable system for cellulose etherification. In this way, we could provide a simple, pollution-free, and homogeneous aqueous solution system for synthesizing cellulose ethers. 相似文献
4.
C. Carnero Ruiz 《Colloid and polymer science》1995,273(11):1033-1040
With the aim of studying the effect of urea on micellar properties of aqueous solutions of sodium dodecylsulfate (SDS), steadystate fluorescence experiments were carried out with different luminescence probes incorporated into the micellar phase. The increase of critical micelle concentration (CMC) of the surfactant with urea addition was followed by changes in the relative intensities of the vibrational fine structure of the pyrene fluorescence spectra. Micellar aggregation numbers were obtained from the analysis of fluorescence quenching data using ruthenium tris(bipyridyl) chloride and 9-mehylanthracene as a donorquencher pair. It was found that the decrease in the aggregation number is mainly controlled by rise in the surface area per headgroup of the surfactant. From fluorescence measurements, using several ionic probes (8-anilino-1-naphthalen-sulfonic acid, rhodamine B, and auramine O), it was found that urea decreases the polarity and increases the microviscosity of the micellar interface. These effects, which are dependent on the concentration of urea, can be explained according to a direct interaction of urea at the micellar surface. 相似文献
5.
Regenerated cellulose (RC)/alginic acid (AL) blend membranes were satisfactorily prepared from 6 wt % NaOH/4 wt % urea aqueous solution by coagulating with 5 wt % CaCl2 aqueous solution, and then treated with 3 wt % HCl. Morphology, crystallinity, mechanical properties, and thermal stability of the membranes were investigated by scanning electron microscopy (SEM), IR and UV spectroscopes, X‐ray diffraction, tensile tests, and thermogravimetric analysis (TGA). The RC/AL blends were miscible in all weight ratios of cellulose to alginate. The membranes have homogeneous mesh structures, and the mesh sizes of the blend membranes (200–2000 nm) significantly increased with increasing alginate content. The crystalline state of the AL membrane prepared from 6 wt % NaOH/4 wt % urea aqueous solution was broken completely, and the crystallinity of the blend membranes decreased with an increase of AL. Comparing with AL membranes, the tensile strength and breaking elongation of the blend membranes were obviously improved in dry and wet states. Therefore, the RC/AL blends offer a promising way of alginate as separate and functional materials used in the wet state. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 451–458, 2001 相似文献
6.
Haisong Qi Jie Cai Lina Zhang Yoshiharu Nishiyama Aurélie Rattaz 《Cellulose (London, England)》2008,15(1):81-89
Cellulose multi-filament fibers have been spun successfully on a pilot plant scale, from a cellulose dope in 7 wt% NaOH/12 wt%
urea aqueous solution pre-cooled to −12 °C. Coagulation was accomplished in a bath with 10 wt% H2SO4/12 wt% Na2SO4 and then 5 wt% H2SO4 aqueous solution. By using different finishing oil, including H2O, 4% glycerol aqueous solution, 2% polyvinyl alcohol (PVA) aqueous solution, 2% polyethylene glycol octyl phenylether (OP)
aqueous solution, mobol and 2%glycerol/1%PVA/1%OP aqueous solution (PGO), we prepared six kinds of the cellulose multi-filaments,
with tensile strength of 1.7–2.1 cN/dtex. Their structure and properties were investigated with scanning electron microscope
(SEM), 13C NMR solid state, wide-angle X-ray diffraction (WAXD) and tensile testing. The cellulose fibers treated with PGO possessed
higher mechanical properties and better surface structure than others. Interestingly, although the orientation of the cellulose
multi-filaments is relatively low, the tensile strength of the single-fiber was similar to that of Lyocell. It was worth noting
that the dyeability of the multi-filament fibers was superior to viscose rayon. 相似文献
7.
Structure and solution properties of cyanoethyl celluloses synthesized in LiOH/urea aqueous solution
Cyanoethyl celluloses (CECs) with different degree of substitution (DS) were synthesized by homogeneous reaction of cellulose
(cotton linter pulp and absorbent cotton) with acrylonitrile (AN) in LiOH/urea aqueous solutions. The reaction showed quick
reactivity and high transfer efficiency of etherification agent. The DS values of CECs were controlled by varying the molar
ratio of AN to anhydroglucose unit (AGU) and the cellulose concentration. The DS values of the CEC-1–CEC-10 increased from
0.27 to 1.78 with increasing molar ratio of AN to AGU from 0.5:1 to 9:1. While the CEC-11–CEC-21 with DS values of 0.26–1.81
could be obtained by adjusting the molar ratio from 1:1 to 27:1. The relative reactivity of hydroxyl groups is in the order
of C-6 > C-2 > C-3. The DS values of the water-soluble derivatives are in the range of 0.47–1.01. As the DS values increase
to 1.37, CEC samples can not be dissolved in water or dilute alkali solution, but have good solubility in organic solvents,
such as DMSO, DMF and pyridine. The dilute solution properties and molecular parameters of the CEC samples were studied by
static light scattering and dynamic light scattering. The results indicated that the water-soluble samples could form a small
number of aggregates spontaneously in 0.9 wt% NaCl aqueous solution, while the water-insoluble samples showed extended stiff
chains in 0.5% LiCl–DMAc. 相似文献
8.
Bharatiya B Aswal VK Hassan PA Bahadur P 《Journal of colloid and interface science》2008,320(2):452-459
Micellization behavior of an amphiphilic ethylene oxide-propylene oxide-ethylene oxide tri-block copolymer Pluronic P85 [(EO)(26)(PO)(39)-(EO)(26)] in aqueous solution and in the presence of a hydrophobic C(14)diol (also known as Surfynol104) was examined by physico-chemical methods such as viscometry, cloud point (CP) and scattering techniques viz. dynamic light scattering (DLS) and small angle neutron scattering (SANS). The addition of diol decreases the cloud point and gelation temperature of aqueous Pluronic P85 copolymer solution. DLS and SANS measurements of the polymer in aqueous solution indicated micellar growth and sphere to rod transition in the presence of diol. Surfynol 104 is a sparingly water soluble diol surfactant with a solubility of approximately 0.1 wt%. However, up on addition to Pluronic solution, diol gets incorporated in the block copolymer micelles and leads to structural transition of the micelles. An increase in the temperature and the presence of added sodium chloride in the solution further enhances this effect. The addition of hydrophobic C(14)diol increases the hydrodynamic size and aggregation numbers of the micellar system. The micellar parameters for the copolymer in the presence of C(14)diol are reported at different temperatures and added sodium chloride concentrations. 相似文献
9.
The mixed micelles of sodium dodecyl sulphate (SDS) with Brij35 and Brij 97 were studied separately by fluorescence measurement using pyrene as fluorescent probe. In the range of 0–1.0 mole fraction (X) of added SDS to Brij solutions, the cmc value of the mixed micelles varies from 0.085 to 8 mmol with Brij 35 and 0.04 to 8 mmol with Brij 97. The aggregation number also changes. A measure of the stability of mixed micelles is also presented. The interaction parameter 12 and the chain–chain contribution parameter (B1) are extracted from the analysis of the results. This parameter B1 is related to the standard free energy change associated with the introduction of one ionic species into a nonionic micelle coupled with the release of one nonionic species from the micelle. The clouding behaviour of Brij 97 in the presence of SDS was investigated and the associated thermodynamic parameters of clouding were generated and discussed. 相似文献
10.
Rapid dissolution of cellulose in LiOH/urea and NaOH/urea aqueous solutions was studied systematically. The dissolution behavior and solubility of cellulose were evaluated by using (13)C NMR, optical microscopy, wide-angle X-ray diffraction (WAXD), FT-IR spectroscopy, DSC, and viscometry. The experiment results revealed that cellulose having viscosity-average molecular weight ((overline) M eta) of 11.4 x 104 and 37.2 x 104 could be dissolved, respectively, in 7% NaOH/12% urea and 4.2% LiOH/12% urea aqueous solutions pre-cooled to -10 degrees C within 2 min, whereas all of them could not be dissolved in KOH/urea aqueous solution. The dissolution power of the solvent systems was in the order of LiOH/urea > NaOH/urea > KOH/urea aqueous solution. The results from DSC and (13)C NMR indicated that LiOH/urea and NaOH/urea aqueous solutions as non-derivatizing solvents broke the intra- and inter-molecular hydrogen bonding of cellulose and prevented the approach toward each other of the cellulose molecules, leading to the good dispersion of cellulose to form an actual solution. 相似文献
11.
New amphiphilic[60]fullerene monoadduct TPF and bisadducts BTPF were synthesized and well-characterized. Their aggregation properties in aqueous solution was investigated by UV-vis and TEM methods. In aqueous solution, monoadduct TPF forms irregularly shaped and some rod-like aggregates, whereas bisadducts BTPF gives sphadcal aggregates with diameters of 50-150 rim. It indicated that the aggregation properties of amphiphilic fullerene derivatives depend on the number of hydrophilic 相似文献
12.
Yanping Yang Yue Zhang Ahmed Dawelbeit Ya Deng Yuxi Lang Muhuo Yu 《Cellulose (London, England)》2017,24(10):4123-4137
Regenerated cellulose fibers were successfully prepared through dissolving cotton linters in NaOH/thiourea/urea aqueous solution at ?2 °C by a twin-screw extruder and wet-spinning process at varying precipitation and drawing conditions. The dissolution process of an optimized 7 wt% cellulose was controlled by polarizing microscopy and resulted in a transparent and stable cellulose spinning dope. Rheological investigations showed a classical shear thinning behavior of the cellulose/NaOH/thiourea/urea solution and a good stability towards gelation. Moreover, the mechanical properties, microstructures and morphology of the regenerated cellulose fibers were studied extensively by single fiber tensile testing, X-ray diffraction, synchrotron X-ray investigations, birefringence measurements and field-emission scanning electron microscopy. Resulting fibers demonstrated a smooth surface and circular cross-section with homogeneous morphological structure as compared with commercial viscose rayon. At optimized jet stretch ratio, acidic coagulation composition and temperature, the structural features and tensile properties depend first of all on the drawing ratio. In particular the crystallinity and orientation of the novel fibers rise with increasing draw ratio up to a maximum followed by a reduction due to over-drawing and oriented crystallites disruption. The microvoids in the fiber as analysed with SAXS were smaller and more elongated with increasing drawing ratio. Moreover, a higher tensile strength (2.22 cN/dtex) was obtained in the regenerated fiber than that of the viscose rayon (2.13 cN/dtex), indicating higher crystallinity and orientation, as well as more elongated and orientated microvoid in the regenerated fiber. All in all, the novel extruder-based method is beneficial with regard to the dissolution temperature and a simplified production process. Taking into account the reasonable fiber properties from the lab-trials, the suggested dissolution and spinning route may offer some prospects as an alternative cellulose processing route. 相似文献
13.
The morphology and structure of the regenerated cellulose membranes prepared from its NaOH–urea aqueous solution by coagulating
with 5 wt% H2SO4–10 wt% Na2SO4 aqueous solution with different temperatures and times were investigated. The pore size, water permeability and physical properties
of the membranes were measured with scanning electron micrograph (SEM), wide X-ray diffraction (WXRD), Fourier transfer infrared
spectroscopy (FTIR), flow rate method, and tensile testing. The SEM observation revealed that the structure and pore size
of the membranes changed drastically as a function of the coagulation temperature. The membranes coagulated at lower temperatures
tended to form the relatively small pore size than those at higher temperatures. On the contrary, the membranes coagulated
at different times exhibited similar pore size. Interestingly, the mean pore size and water permeability of the membranes
increased from 110 nm with standard deviation (SD) of 25 nm and 12 ml h−1 m−2 mmHg−1 respectively to 1,230 nm with SD of 180 nm and 43 ml h−1 m−2 mmHg−1 with an increase in coagulation temperature from 10 to 60°C. However, the membranes regenerated below 20°C exhibited the
dense structure as well as good tensile strength and elongation at break. The result from FTIR and ultraviolet-visible (UV-vis)
spectroscopy indicated that the relatively strong intermolecular hydrogen bonds exist in the cellulose membranes prepared
at lower coagulation temperatures. This work provided a promising way to prepare cellulose materials with different pore sizes
and physical properties by controlling the coagulation temperature. 相似文献
14.
When aqueous solution of aluminium salt involving nitrate, chloride or sulfate was added into sodium fluoride solution, an immediate reaction occured to form cryolite-like precipitate. Examination into the resultant solution and analysis for the precipitate were carried out, leading to the fact that fluorine ion can substitute for bound water molecules around central Al+++ ion, but hardly for bound hydroxide and sulfate ion which should go or be “frozen”, as it is, into cryolite-like precipitate. These ligand substitution reaction seems to contribute to identification of ion species of aluminium in aqueous solution. 相似文献
15.
《Physics and Chemistry of Liquids》2012,50(1):88-101
Volumetric, viscometric and ultrasonic studies of uracil in an aqueous urea solution in varying concentration of 2, 3 and 5?M have been carried out at 298, 308 and 318?K. The uracil concentration in the aqueous urea solution varies from 0.05% to 0.4%. Density (ρ), viscosity (η) and sound speed (u) have been measured. The experimental data are used for computing various thermodynamic and acoustic parameters, namely apparent molar volume, isentropic compressibility, apparent isentropic compressibility, relative association, intermolecular free length, acoustic impedance, viscous relaxation time, hydration number, Gibb's free energy, classical absorption coefficient of the solution and viscosity data have been further analysed in the light of Masson's equation and Jones–Dole's equations, respectively. The results have been discussed in terms of solute–solute and solute–solvent interaction and the structural changes of the solutes in solutions. The effect of variation of temperature on these interactions has also been investigated. 相似文献
16.
Aqueous 5 wt% LiOH/12 wt% urea solution pre-cooled to −12 °C has a more powerful ability to dissolve cellulose compared to
that of NaOH/urea and NaOH/thiourea solution system. The influences of the cellulose concentration and coagulation temperature
on the structure, pore size and mechanical properties of the cellulose films prepared from LiOH/urea system were investigated.
The cellulose films exhibited good mechanical properties either at wet or dry state and their pore size and water permeability
at wet state can be controlled by changing the cellulose concentration or coagulation temperature. With a decrease of the
coagulation temperature, the mechanical properties and optical transmittance of the cellulose films enhanced, as a result
of the formation of relative smaller pore size and denser structures. This work provided a promising way to prepare cellulose
films with different pore sizes at wet state and good physical properties at dry state. 相似文献
17.
Micellization behavior of the twin-tailed surfactants can be modulated by the addition of various modifiers. Ionic liquids (ILs) are one of them and are documented here. The beauty of these environmentally benign neoteric molecules lies in their structural versatility. Here, we have investigated the effect of three ILs: 1-butyl-3-methylimidazolium bromide ([C4mim][Br]), 1-hexyl-3-methylimidazolium bromide ([C6mim][Br]), and 1-octyl-3-methylimidazolium bromide ([C8mim][Br]) on the aggregation and surface adsorption behavior of cationic gemini surfactant, bis(hexadecyldimethyl ammonium)propane dibromide (16-3-16) through experimentally measured electrical conductivities, surface tensions, and by spectral methods (UV-vis absorbance and fluorescence measurements). The main focus of the study is to observe the effect of added ILs on the critical micelle concentration (cmc), various surface parameters, aggregation number, and size of the aggregates of gemini surfactant. The results show that the more hydrophobic ILs, that is, [C6mim][Br] and [C8mim][Br] behave as electrolyte at lower concentration and cosurfactant at higher concentration, whereas moderately hydrophobic IL [C4mim][Br] acts as an electrolyte at all concentration ranges studied. The modulating effects of ILs were also compared with conventional electrolyte (NaBr) at similar conditions. 相似文献
18.
Jinping Zhou Lina Zhang Qinghai Deng Xiaojun Wu 《Journal of polymer science. Part A, Polymer chemistry》2004,42(23):5911-5920
We successfully synthesized hydroxypropylcellulose (HPC) and methylcellulose (MC) in high yields from cellulose in 6 wt % NaOH/4 wt % urea aqueous solutions at 25 °C. The cellulose derivatives were characterized with NMR, size exclusion chromatography/laser light scattering, gas chromatography (GC), ultraviolet, and solubility measurements in different solvents. According to the results of solution 13C NMR and GC, the individual degree of substitution (DS; i.e., the average number of substituted hydroxyl groups in the monomer unit) at C‐2 hydroxyl groups was slightly higher than the DS values at C‐3 and C‐6 hydroxyl groups for HPC and MC. In comparison with traditional systems, NaOH/urea aqueous solutions were proved to be a stable and more homogeneous reaction medium for preparing cellulose ether with a more uniform microstructure. The low limits for the average number of moles of the substituent groups per monomer unit and the DS value of water‐soluble HPC were 1.03 and 0.85, respectively. MC (DS = 1.48) had good solubility in both water and organic solvents, and the precipitation point occurred at about 67 °C for a 2% (w/v) aqueous solution. In this way, we could provide a simple, pollution‐free, and homogeneous aqueous solution system for synthesizing cellulose ethers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5911–5920, 2004 相似文献
19.
Aqueous solution of anionic surfactant,sodium oleate(NaOA),was studied by means of steady-state shear rheology and dynamic oscillatory technique.The system of NaOA/Na3PO4 showed high viscosity,strong viscoelasticity and good ability of countering Ca^2+,Mg^2+.The Maxwell model and Cole-Cole plot were applied to study the dynamic viscoelasticity of wormlike micelles.The microstructures of the wormlike micelles were characterized by FF-TEM. 相似文献
20.
Guido Barone Giuseppina Castronuovo Vittorio Elia Massimo Muscetta 《Journal of solution chemistry》1986,15(2):129-140
The interaction in water of urea, monomethylurea, monoethylurea, monopropylurea, and monobutylurea with -cyclodextrin(hexacycloamylose) was studied calorimetrically at 25°C. The results show that the last three substances form inclusion complexes with -cyclodextrin. The enthalpy and the association constants relative to the inclusion process were determined. The association constant values are low, indicating weak complexing that increases with increasing length of the alkyl chain. Urea and monomethylurea, on the other hand, do not form inclusion complexes. For these systems the calorimetric data were treated in terms of excess enthalpies, and the McMillan-Mayer approach was used to get an insight into the weak, non-bonding molecular interactions occurring in these solutions.Presented at the sixth Italian meeting on Calorimetry and Thermal Analysis (AICAT) held in Naples, December 4–7, 1984. 相似文献