共查询到20条相似文献,搜索用时 15 毫秒
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Halima Alem 《Polymer Degradation and Stability》2010,95(3):327-331
Surface initiated polymerization of N(isopropylacrylamide) (NIPAM) was performed by controlled radical polymerization on PET track-etched membranes presenting two different pore diameters (narrow pores: ∼80 nm and large pores: ∼330 nm). The opening and closing characteristics of the resulting PNIPAM-g-PET membranes were investigated by conductometric measurements carried out at different temperatures below and above the LCST of PNIPAM and in the presence of different salts. Depending on the membrane pore size, two types of permeation control mechanisms are observed. In large pore membranes, expanded PNIPAM chains conformations result in reduced effective pore size and therefore lower permeabilities relative to collapsed macromolecules chain conformations. In contrast, in narrow pore membranes, the expanded PNIPAM brush presents greater degrees of hydration in the surface layer and therefore gives rise to higher permeabilities than the collapsed conformation. In this situation, the overall permeability is thus comparable to that of a hydrogel membrane. 相似文献
3.
Friction and adsorption of aqueous polyoxyethylene (Tween) surfactants at hydrophobic surfaces 总被引:1,自引:0,他引:1
Graca M Bongaerts JH Stokes JR Granick S 《Journal of colloid and interface science》2007,315(2):662-670
The nanotribological responses of a series of nonionic polyoxyethylene surfactants (Tween 20, Tween 40, Tween 60, and Tween 80) were investigated after they were adsorbed from aqueous solution onto atomically smooth hydrophobic substrates. The hydrophobic surfaces were composed of a condensed monolayer of octadecyltriethoxysilane (OTE; contact angle theta>110 degrees ). The nanorheological measurements were performed using a modified surface forces apparatus after coating atomically smooth mica with these OTE monolayers, while adsorption measurements were performed using phase-modulated ellipsometry on silicon wafers coated with these same monolayers. The minimum surface-surface separation observed under high load in friction studies agreed quantitatively with the thickness obtained from ellipsometry. For Tweens 20, 40, and 60, the thickness of the adsorbed film increases with increasing alkyl chain length. Systematic investigations of the nanorheological response showed that there is a "solid-like" elastic response from confined surfactant layers, which is the case for the smallest separations to separations up to slightly larger than twice the adsorbed film thickness. In kinetic friction, these confined layers are characterized by a shear stress of approximately 3 MPa with minimal dependence on shear rate. The magnitude of the sliding shear stress is the same as the apparent yield stress at approximately 3 MPa; it is independent of alkyl chain length within the Tween family of surfactants and corresponds to a nominal friction coefficient of mu approximately 1. A similar friction coefficient is observed for boundary lubrication on the macroscopic scale in a tribometer utilizing hydrophobic surfaces and mu approximately 1.1 for Tweens 20, 40, and 60. These results suggest that while Tween molecules adsorb onto hydrophobic surfaces to form a robust separating layer, the lubricating properties of these layers are dominated by a highly dissipative slip plane, the same for all alkyl chain lengths. 相似文献
4.
J. S. Hong T. Nakahara H. Maeda Y. Kikunaga A. Kishida M. Akashi 《Colloid and polymer science》1996,274(11):1013-1019
Aqueous poly(N-vinylacetamide) (PNVA) solution was found to exhibit the cloud point in the presence of salt. This cloud point was shown to correspond to a liquid-liquid phase separation, as confirmed when the PNVA-salt solutions were maintained at a temperature above the cloud point. The upper layer had a higher polymer concentration and a lower salt concentration than those in the lower layer. Thus interaction between PNVA and salts are repulsive. The lower critical solution temperatures were estimated to be 18±1°C for 1.25 molal (NH4)2SO4 and 25±1°C for 0.76 molal Na2SO4. Divalent anions such as SO
2–
4
, SO
2–
3
, HPO
2–
4
and CO
2–
3
were effective in causing turbidity when examined at 25°C. Dependence of the effect on the cationic species was similar to but significantly different from that for acetyltetraglycine ethylester. The cloud points of PNVA decreased linearly with the increase of the polymer concentration at a fixed salt concentration or with the increase of the salt concentration at a fixed polymer concentration. A parameter analogous to the salting-out constant was empirically derived from the dependencies of the cloud points on the concentrations of polymer and salt. 相似文献
5.
S. N. Petrova M. V. Volodarskii S. V. Makarov Lu Zhen Li 《Russian Journal of Applied Chemistry》2008,81(9):1573-1577
Degradation of Direct Red 23, Rective Red 45, and Orange II azo dyes with hydrogen peroxide and hydroperite in the presence of cationic surfactants alkyldimethylbenzylammonium chloride (Katamin AB) and cetyltrimethylammonium chloride and without them was studied by spectrophotometry. The reactivity of the azo dyes was correlated with their chemical structure. 相似文献
6.
A. M. Elokhov A. E. Lesnov O. S. Kudryashova 《Russian Journal of Inorganic Chemistry》2017,62(9):1267-1273
The effect of salt structure on the ability to salt out oxyphos B from aqueous solutions is elucidated using the solubility data in pseudo-ternary inorganic salt–potassium bis(alkylpolyoxyethylene)phosphate (oxyphos B)–water systems in the temperature range of 20–90°С. The results are interpreted according to the Samoilov’s theory of salting-out. 相似文献
7.
In this paper, we are reporting the influence of addition of aromatic acids (anthranilic and benzoic acid) and their sodium salts on the micellar morphological changes in three cationic gemini surfactant solutions, viz. 5 mM tetramethylene-1,4-bis(N-hexadecyl-N,N-dimethylammonium bromide), 10 mM pentamethylene-1,5-bis(N-hexadecyl-N,N-dimethylammonium bromide), and 10 mM hexamethylene-1,6-bis(N,-hexadecyl-N,N-dimethylammonium bromide). The solubilization site of the counterions (obtained from the additives) near the micellar surface are inferred by 1H NMR. The behavior is explained in the light of binding of counterions to the micelle as well as the nature of the functional group attached to the additive. 相似文献
8.
A field desorption mass spectrometric method is proposed for the analysis of mixtures of surfactant and inorganic salts. Different compounds in the mixture are determined with different heating currents and distinguished on the basis of the exterior character of the mass spectrum. The effectiveness of the method is demonstrated with known mixtures of surfactants and inorganic salts. Two unknown additives for electric tin plating were tested with the method. 相似文献
9.
Hidehiro Kumazawa Eizo Sada Tetsuo Ando 《Journal of polymer science. Part A, Polymer chemistry》1984,22(1):61-67
The concentration-dependence measured by steady-state permeation and unsteady-state dyeing methods for a system of acid dye C.I.Acid Blue 182–nylon 6 film in the presence of inorganic salts such as NaCl, Na2SO4, and K2SO4, was analyzed in terms of parallel diffusion with simultaneous multimodal adsorption. It would found that the dyeing process with added NaCl was governed by surface diffusion with two kinds of Langmuir adsorption, whereas with added Na2SO4 and K2SO4 it was governed by surface diffusion with three kinds of Langmuir adsorption. 相似文献
10.
Haldar J Aswal VK Goyal PS Bhattacharya S 《Journal of colloid and interface science》2005,282(1):156-161
The aggregation properties of single-chain surfactants bearing one (H1), two (H2), and three (H3) trimethylammonium head groups have been studied by small-angle neutron scattering (SANS). Growth of aggregates was observed to decrease dramatically with an increase in the number of head groups in the surfactants. The micelles grow progressively smaller with every increase in the number of head groups of the surfactants. Aggregation number (N) continuously decreases and the fractional charge (alpha) gradually increases with the increase in the number of head groups. The semiminor axis (a) and semimajor axis (b=c) of the micelle decrease strongly with the increase in the number of head groups. In the case of H1, dramatic micellar growth is observed on addition of salts such as KBr and sodium salicylate, but this type of micellar growth is not observed in the cases of H2 and H3 when the above salts are added to their micellar solutions. Aggregation number and size of the micelles remain almost the same, even after addition of KBr at a concentration as high as 100 mM. This observation with multiheaded cationic surfactants is unusual. Clearly, the charge density at the head group level of surfactants markedly influences their micellar aggregation properties. 相似文献
11.
Acrylonitrile polymerization photoinitiated at 365 nm by pyrene and/or azobisisobutyronitrile in the presence of zinc salts in N,N-dimethylformamide solution has been studied by the rotating sector method. It was found that the ratio of the rate constants for propagation and termination (kp/kt) increases on addition of zinc salts (chloride, nitrate, acetate). This increase was more pronounced for the azobisisobutyronitrile photoinitiated polymerization of acrylonitrile then for its pyrene photoinitiated polymerization. The results confirm the previously expressed view concerning the dual role of zinc chloride in initiation as well as in propagation steps of acrylonitrile polymerization photoinitiated by aromatic hydrocarbons.
, 365 / N,N- . , (kp/kt) ( , , ). , . , , , .相似文献
12.
R. D. Lundberg F. E. Bailey R. W. Callard 《Journal of polymer science. Part A, Polymer chemistry》1966,4(6):1563-1577
Evidence is presented for the interaction of metal salts such as potassium iodide with polyethers such as poly(ethylene oxide). This interaction is sufficiently marked that the incorporation of 10–30% of the salt in the bulk polymer markedly reduces crystallinity while retaining compatibility. Examination of electroviscous effects in methanol demonstrates that the salt–polymer adduct behaves as a typical polyelectrolyte at low salt concentrations, while the polymer in absence of salt is essentially insoluble in methanol at room temperature. Measurements of the equilibrium between salt and polymer along with a study of various molecular weight polymers strongly suggest that one salt molecule associates with about nine ethylene oxide units. It is proposed that the association is due to an ion–dipole interaction, and the anion is tentatively postulated as the species directly associating with the polymer. The association of other metal salts and other polymers are interpreted in this light. The significance of these results in interpreting salting-in phenomena is also discussed. 相似文献
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Potentiometric titration was used to determine the dissociation constants of di- and trihydroxybenzenes in a 1: 1 deoxygenated water-ethanol system at a temperature of 293 ± 1 K in the presence of a nonionogenic surfactant, polyoxyethylene sorbitan monooleate (Twin-80). The dissociation constants (pK 1) of phenols without addition of surfactants were evaluated. 相似文献
15.
A. A. Solov’ev M. A. Pashina O. E. Lebedeva 《Russian Journal of Applied Chemistry》2007,80(2):275-278
The influence of inorganic salts on the kinetics of oxidation of 2,4-and 2,6-dinitrophenols by Fenton’s reagent, hydrogen peroxide, in the presence of iron(II) ions was studied. 相似文献
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Carmen Racles Maria Cazacu Gabriela Hitruc Thierry Hamaide 《Colloid and polymer science》2009,287(4):461-470
Siloxane-containing surfactants have been tested as stabilizers for the preparation of polymer nanoparticles by three types
of chemical reactions. Two crosslinking reactions were used to obtain silicone elastomers particles: one involved HO-terminated
polydimethylsiloxane and tetraethoxysilane, while the other one was a crosslinking via polyhydrosilylation. The third reaction
was a linear polycondensation between a diamine and a siloxane dialdehyde. The monitoring of the reactions has been made by
infrared spectroscopy and the resulting particles have been analyzed in dispersion by light scattering and in dry state by
electron microscopy and atomic force microscopy. The particles size was of hundreds of nanometers and their spherical shape
was generally maintained after drying. The spectral and microscopy data proved efficient stabilization, which allowed the
reactions to evolve after the formation of the particles. 相似文献
18.
L. V. Dikhtievskaya A. D. Markin L. F. Shlomina V. V. Shevchuk F. F. Mozheiko 《Russian Journal of Applied Chemistry》2009,82(9):1522-1527
Interfacial tension in the oil/water system in the presence of various ionic surfactants and inorganic electrolytes was studied.
Special features of the effect of the surfactant and oil phase natures, of the structure of their molecules, and also of the
electrolytes containing ions with various radii, valences, and hydratabilities on the value of the interfacial tension were
studied. The criteria and conditions of obtaining model emulsions based on paraffin hydrocarbons and technical emulsions based
on vegetable oils were determined. 相似文献
19.
D. F. Anghel S. Saito A. Băran A. Iovescu M. Corniţescu 《Colloid and polymer science》2007,285(7):771-779
The solution properties of homogeneous hexaethylene and octaethylene glycol mono(n-dodecyl) ethers, C12E6 and C12E8, respectively, and octaethylene glycol mono(n-decyl) ether, C10E8, with poly(methacrylic acid) (PMA) were investigated by dye solubilization, surface tension, fluorescence, viscosity, and
pH measurements. The data were discussed regarding non-cooperative and cooperative binding of surfactant to polymer. Whereas
in the interaction with poly(acrylic acid) (PAA), the critical aggregation concentrations (cac or T
1) of these surfactants were lower than the respective critical micelle concentration (cmc), in that with the more hydrophobic
PMA, T
1’s of C12E6 and C12E8 were higher than the respective cmc, but that of C10E8 was lower than its cmc. These may be ascribed to the hydrophobic microdomains (HMD) of the PMA coil in water, probably in
its inside. It is considered that some surfactants are bound first to the HMD non-cooperatively and then they are abruptly
bound cooperatively at T
1. This raises T
1 higher than cmc when the cmc is low, and the amount bound by the HMD is relatively large and vice versa. T
1 of C12E6 or C12E8 is the former case, and that of C10E8 is the latter. Thus, different from PAA, T
1 for PMA + nonionic surfactant system consists of the amount of non-cooperative binding and the cac of the cooperative binding
in equilibrium. Therefore, this T
1 has a different meaning from that for PAA and should be called apparent T
1. As the binding to the HMD is dependent on PMA concentration and cac is not, which is like in the PAA system, separation
of apparent T
1 from the HMD binding was achieved by extrapolating T
1’s to zero PMA concentration (denoted intrinsic T
1). This value for C12E8 was found to be lower than the respective cmc and also lower than the respective T
1 for PAA. With increase in surfactant concentration, the pH of PMA solution rose and demonstrated a peak. This pH rise and
fall may be induced by loosening of the HMD coil due to binding increase and by rearrangement of PMA + surfactant complex
in high surfactant concentrations region. By raising the initial pH, the HMD were loosened; consequently, T
1 rose a little, and at higher pH, no surfactant binding took place. 相似文献
20.
Yu. I. Sal’nikov G. A. Boos I. S. Ryzhkina S. S. Lukashenko D. N. Manzhukova 《Colloid Journal》2006,68(5):607-612
Aggregation and protolytic properties of bis(dimethylaminomethyl)phenols containing methyl (HA) and nonyl (HL) substituents at the benzene ring are studied in aqueous solutions of isopropanol and various surfactants with potentiometric titration, tensiometry, and mathematical modeling of equilibria. Monomers, dimers, and tetramers of HA and HL are found. It is shown that the degree of compound aggregation depends on the solution concentration and pH. Sodium dodecyl sulfate and HA form associates, whereas SDS and HL form mixed micelles at the CMC-1 and CMC-2 critical micellization concentrations. In micellar solutions of Triton X-100 and cetyltrimethylammonium bromide, the mixed micelles are not found via tensiometry. Protonated species of tetramer, dimer, and monomer of investigated compounds are revealed, depending on the acidity of the medium. Phenolate forms of HA and HL do not exist under experimental conditions. Apparent protonation constants are determined and it is shown that, for the HA compound that does not form micelles, the protonation constants of the same-type species increase in the presence of the three surfactants used as compared to the water-isopropanol solution. Decreasing constants of analogous HL forms in the solutions of CTAB, nonionic surfactant (C Tx = 10 mM), and SDS (pH > 7) are attributed to the formation of associates or mixed micelles of this compound and surfactants under experimental conditions. 相似文献