共查询到20条相似文献,搜索用时 15 毫秒
1.
D. J. Allen S. M. Neale P. J. T. Tait 《Journal of Polymer Science.Polymer Physics》1972,10(3):433-448
Measurements are reported for the dielectric loss factor of the SCMC solutions over the frequency range 2 MHz to 50 MHz as a function of concentration of SCMC, concentration of added sodium chloride, molecular weight, and temperature. The results are in general agreement with those of other workers and are interpreted in terms of ionic theories in which motion of the diffuse counterions is the dominant feature. 相似文献
2.
Carlos G. Lopez Sarah E. Rogers Ralph H. Colby Peter Graham João T. Cabral 《Journal of Polymer Science.Polymer Physics》2015,53(7):492-501
We report a small angle neutron scattering (SANS) and rheology study of cellulose derivative polyelectrolyte sodium carboxymethyl cellulose with a degree of substitution of 1.2. Using SANS, we establish that this polymer is molecularly dissolved in water with a locally stiff conformation with a stretching parameter . We determine the cross sectional radius of the chain ( 3.4 Å) and the scaling of the correlation length with concentration (ξ = 296 c?1∕2Å for c in g/L) is found to remain unchanged from the semidilute to concentrated crossover as identified by rheology. Viscosity measurements are found to be in qualitative agreement with scaling theory predictions for flexible polyelectrolytes exhibiting semidilute unentangled and entangled regimes, followed by what appears to be a crossover to neutral polymer concentration dependence of viscosity at high concentrations. Yet those higher concentrations, in the concentrated regime defined by rheology, still exhibit a peak in the scattering function that indicates a correlation length that continues to scale as . © 2014 The Authors. Journal of Polymer Science Part B: Polymer Physics Published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 492–501 相似文献
3.
L.-M. Zhang 《Colloid and polymer science》1999,277(9):886-890
Homogeneous blends of two solutions of carboxymethylcellulose and hydroxyethylcellulose (HEC) were studied with respect to
viscosity properties at different blending ratios, shear rates and temperatures. The blends exhibited viscosity synergism
at all blending ratios, as well as improved shear and temperature stability. Maximum synergism was observed for the blend
containing 67% of HEC. The UV and IR spectra showed that the hydrogen-bonding interaction between the blended components is
the main reason for the synergism.
Received: 9 February 1999 Accepted in revised form: 15 April 1999 相似文献
4.
A. M. Bochek N. M. Zabivalova V. E. Yudin I. V. Gofman V. K. Lavrent’ev B. Z. Volchek E. N. Vlasova I. V. Abalov N. G. Brusilovskaya I. I. Osovskaya 《Polymer Science Series A》2011,53(12):1167-1174
The rheological properties of carboxymethyl cellulose aqueous solutions containing small amounts of purified montmorillonite
and bentonite nanoparticles are studied. The viscosity of mixed solutions decreases after addition of 1 wt % nanoparticles.
X-ray diffraction analysis shows that the films contain nanoparticles in the exfoliated state. An examination of the FTIR
spectra of composite films suggests a shift in the absorption band due to Si-O groups. This phenomenon may be explained both
by a change in the permittivity of the nanoparticle environment and by the formation of hydrogen bonds between Si-O groups
and functional groups of cellulose ether. It is shown that the content of the added nanoparticles influences the mechanical
characteristics of the films prepared from the systems of interest. 相似文献
5.
L. M. Trufakina 《Russian Journal of Applied Chemistry》2006,79(12):2013-2015
Rheological properties of aqueous solutions of carboxymethyl cellulose, polyvinyl alcohol, and of their blends prepared under various conditions (temperature, concentration, time) were studied by viscometry and of ball indenter penetration. 相似文献
6.
O. Ya. Uryupina V. V. Vysotskii V. V. Matveev A. V. Gusel’nikova V. I. Roldughin 《Colloid Journal》2011,73(4):551-556
It is shown that gold nanoparticles can be produced using cellulose ethers, methylhydroxyethyl cellulose, and carboxymethyl cellulose as reducing agents that also play the role of nanoparticle stabilizers. Depending on the synthesis conditions, nanoparticle sizes vary in the range of 20–100 nm. The application of carboxymethyl cellulose as a stabilizer may give rise to the formation of a bimodal ensemble of nanoparticles with sizes of 4–5 and 30–40 nm. The differences in the mechanisms for the reduction and stabilization of gold nanoparticles in the presence of these cellulose derivatives are established by IR spectroscopy. The obtained colloidal dispersions of gold nanoparticles remain stable for a long time. 相似文献
7.
Size dependences of silver nanoparticles synthesized in aqueous carboxymethyl cellulose solutions and dependences of their ζ-potentials on solution pH are studied by the dynamic light scattering method. Variations in nanoparticle size distributions and ζ-potential of particles with time are monitored. It is revealed that the size of silver nanoparticles decreases linearly with an increase in solution pH. The size of particles noticeably decreases in the aging process of the colloidal solution. The ζ-potential tends to one and the same value with time for all studied hydrosol samples. 相似文献
8.
Bochek A. M. Shevchuk I. L. Kalyuzhnaya L. M. 《Russian Journal of Applied Chemistry》2010,83(4):712-717
Russian Journal of Applied Chemistry - The rheological properties of dilute and moderately concentrated aqueous solutions of blends of polyvinyl alcohol with carboxymethyl cellulose ionized to... 相似文献
9.
M. V. Radugin T. N. Lebedeva A. N. Prusov A. G. Zakharov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(10):1863-1865
The enthalpy of interaction between cellobiose and sodium carboxymethyl cellulose, methyl cellulose, and 2-hydroxyethyl cellulose
in water is determined. The exothermal nature of the interaction between cellulose and cellulose ethers is established. The
strongest intermolecular interaction is found between cellobiose and 2-hydroxyethyl cellulose. The results are discussed in
the context of the polysaccharide molecular structure. 相似文献
10.
《Radiation Physics and Chemistry》1999,53(2):165-170
Radiolytic reduction of silver, copper and cadmium ions and the subsequent formation of their clusters was studied in aqueous gelatin or carboxy methyl cellulose (CMC) solutions. Presence of gelatin or CMC in the solution affects the early processes. The rate of reduction by hydrated electron reduces due to complexation. However, when the ratio of silver ions to monomeric chains decreases over a certain limit the process of reduction inhibits completely. The effect of ionic strength or pH and the reducing radical on the rate of formation of colloidal Cu and Cd is also discussed. 相似文献
11.
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
12.
In this study, we investigated the way of predicting two critical concentrations of sodium carboxymethyl cellulose (CMC) solutions
using simple experimental procedures with a rotational rheometer. It was found that, above a critical shear rate, all CMC
solutions (0.2 to 7 wt.%) exhibit shear-thinning behavior and the flow curves could be described by the Cross model. A first
critical CMC concentration c*, transition to semidilute network solution, was determined using the following methods (1) study of the flow curve shapes, (2) Cross model parameters, (3) plot of the specific viscosity vs the overlap parameter, and (4) empirical structure–properties relationships. Furthermore, both creep and frequency-sweep measurements showed that the solutions
behaved as viscoelastic materials above a second critical CMC concentration c** (transition to concentrated solution). The characterization of CMC solutions was completed with a time-dependent viscosity
study that showed that the CMC solutions exhibited strong thixotropic behavior, especially at the highest CMC concentrations. 相似文献
13.
Loan T. T. Trinh Anna-Lena Kjøniksen Kaizheng Zhu Kenneth D. Knudsen Sondre Volden Wilhelm R. Glomm Bo Nyström 《Colloid and polymer science》2009,287(12):1391-1404
In this work, the salt-induced aggregation of bare and polymer-covered silver particles has been studied with the aid of light
scattering and UV-visible spectroscopy. Light scattering on a suspension of bare silver particles at a low salt concentration
shows that the cluster fractal dimension d
f changes from 1.6 to 2 in the course of the aggregation process, whereas no restructuring of the clusters is observed at a
higher salinity where d
f ≈ 1.6. The growth of the clusters over time can be described by a power law R
h ∝ t
α
, where R
h is the apparent hydrodynamic radius. The UV-visible experiments revealed that increasing the size of the bare silver particles
lead to a significant broadening and red-shift of the absorbance band, whereas for salt-induced growth of Ag clusters, a blue-shift
and broadening was observed. Addition of salt to a suspension of silver particles and hydroxyethylcellulose divulged a slower
broadening of the surface plasmon peak than without polymer. 相似文献
14.
Water-soluble, partially hydrophobized polysaccharides have become attractive due to their potential to act as polymeric surfactants.
From carboxymethyl starch (CMS), water-soluble polymeric surfactants were prepared by esterification using two unconvential
methods based on (A) a reaction with mixed anhydrides and (B) with methyl laureate (MELA) and methyl esters of the fatty acid
complex of rape seed oil (MERO) under ‘solvent-free’ conditions. The obtained CMS derivatives were characterized by structural,
surface-active and surfactant performance properties. Esterification using method B was successful in contrast to method A
which yielded derivatives with a very low extent of esterification. Although the derivatives reduced the surface tension moderately,
they exhibited remarkable emulsifying properties. The performance tests indicated good washing power and antiredeposition
efficiency. The results suggest that suitable polymeric surfactants can be prepared by the unconventional esterification method
B using both acylation agents. The preparations might substitute the expensive and invasive industrially applied conventional
methods. 相似文献
15.
A morphological study of hydroxypropyl cellulose (HPC) was performed on solid films prepared by casting from a liquid-crystalline aqueous solution at rest or under shear. Electron microscopic observations reveal that many round particles composed of stacked disks are densely packed in the interior of a quiescently cast HPC film, while on the film surface formation of fibrous textures is also noted. Shear-deformed HPC films exhibit some interesting morphological features according to the shearing conditions. It is found by electron microscopy that the originally round particles become more and more elongated as shear stress increases. The resulting rodlike fibrillar entities are considerably aligned in the shear direction (SD), but form a banded structure with periodic discontinuities of molecular orientation distribution along the SD. A new mechanism of structural transformation is proposed in order to interpret these results. 相似文献
16.
The adsorption of carboxymethyl starch (CMS) at the alpha-alumina/aqueous solution interface has been investigated through adsorption studies, electrokinetics mobility measurements, and FTIR spectroscopy. Zeta potential measurements show that the addition of CMS results in a more dramatic increase in the absolute zeta potential in the alkaline region, as well as a shift of the isoelectric point to lower values, indicating the adsorption of CMS from the aqueous solution onto the alumina surface. The positive hydrophilic surface sites of alumina are responsible for the adsorption of CMS molecules. The adsorption of CMS is possible after charge reversal by the addition of excess CMS. Nearly 30 min of contact time are found to be sufficient for the adsorption of CMS to reach equilibrium. CMS adsorption follows a Langmuir isotherm with adsorption capacities of 91.74 mg CMS per gram of alpha-alumina. For the adsorption of CMS, pseudo-second-order chemical reaction kinetics provides the best correlation with the experimental data. FTIR analysis indicated that CMS forms outer complexes with alumina surfaces depending on the shifting of the asymmetric and symmetric bands. 相似文献
17.
Water-soluble deoxy-azido cellulose derivatives were synthesized by heterogeneous carboxymethylation, applying 2-propanol/aqueous NaOH as slurry medium. The novel, carboxymethyl deoxy-azido cellulose provides a convenient starting material for the selective dendronization of cellulose via the copper-catalyzed Huisgen reaction yielding water-soluble carboxymethyl 6-deoxy-(1-N-[1,2,3-triazolo]-4-polyamidoamine) cellulose derivatives of first (degree of substitution, DS 0.51), second (DS 0.44) and third generation (DS 0.39). The novel biopolymer derivatives were characterized by FT-IR and NMR spectroscopy, intrinsic viscosity, sedimentation coefficient and weight average molar mass. Solution conformation and flexibility were estimated qualitatively using conformation zoning and quantitatively (persistence length) using the combined global method. Sedimentation conformation zoning showed a semi-flexible coil conformation and the global method applied to each carboxymethyl deoxy-azido cellulose and carboxymethyl 6-deoxy-(1-N-[1,2,3-triazolo]-4-polyamidoamine) cellulose derivative yielded persistence length all within the range of 2.8-4.0 nm with no evidence of any change in flexibility with dendronization. 相似文献
18.
Aqueous gels of carboxymethylcellulose in the free acid form (HCMC) are obtained when dialyzed sodium carboxymethylcellulose (NaCMC)-gels are treated with a strongly acidic ion exchanger. These gels age rheologically. During the aging process (maximum 60 days), thixotropy and increased viscoelasticity occur. The rheological changes are measured by shear viscosity, coefficient of thixotropy H, complex dynamic shear modulus G*, shear storage modulusG, shear loss modulusG, and tangent of the phase angle. The aging process is caused by the formation of quasi-crystalline microaggregates of HCMC which can be detected by electron microscopy (Part II). 相似文献
19.
20.
It has been reported that cellulose is better dissolved in NaOH-water when a certain amount of urea is added. In order to
understand the mechanisms of this dissolution and the interactions between the components, the binary phase diagram of urea/water,
the ternary urea/NaOH/water phase diagram and the influence of the addition of microcrystalline cellulose in urea/NaOH/water
solutions were studied by DSC. Urea/water solutions have a simple eutectic behaviour with a eutectic compound formed by pure
urea and ice (one urea per eight water moles), melting at −12.5 °C. In the urea/NaOH/water solutions, urea and NaOH do not
interact, each forming their own eutectic mixtures, (NaOH + 5H2O, 4H2O) and (urea, 8H2O), as found in their binary mixtures. When the amount of water is too low to form the two eutectic mixtures, NaOH is attracting
water at the expense of urea. In the presence of microcrystalline cellulose, the interactions between cellulose and NaOH/water
are exactly the same as without urea, and urea is not interacting with cellulose. A tentative explanation of the role of urea
is to bind water, making cellulose-NaOH links more stable.
Member of the European Polysaccharide Network of Excellence (EPNOE), 相似文献