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1.
The potential energy of the total interaction between two spherical colloidal particles of different nature is calculated, i. e., of an ion-penetrable particle and an ion-impenetrable solid particle having a constant surface potential or constant surface charge density. The criteria for heterocoagulation are derived. The obtained results suggest a possibility of selective coagulation in the mixed system. 相似文献
2.
A solid sphere approaches a spherical droplet at small gap widths. The radii of the particles are identical. Potential theory is applied and the problem of interaction brought to the solution of an integrodifferential equation for radial velocity at the droplet/ thin layer interface. Asymptotic formulae are reported for interface velocity and drag force for small and large viscosity ratios. The results are compared with the solutions for a solid sphere and flat tangentially mobile interface. Thus, two major effects may be distinguished: opening of the gap and curving of the streamlines inside the droplets. The latter is shown to cause a relative increase in the drag force. 相似文献
3.
The pair interaction potential for charged macromolecules in solution is calculated from the Ornstein-zernike equation with MSA-closure for the salt-ion/salt-ion and salt-ion/macroion interaction, and HNC-closure for the macroion/macroion interaction. Two different limiting cases are considered: low salt-ion concentration or zero hardcore volume of the macroion. It is found that if the Debye screening length is much larger than the smallest linear dimension of the macroion, the potential is simply a superposition of point-point interaction potentials (screened Coulomb potentials). 相似文献
4.
An analytic, approximate expression for the electrostatic interaction between two membranes immersed in an electrolyte solution is derived on the basis of a simple membrane model. This model assumes that the membrane has a surface layer in which charged groups are uniformly distributed and that electrolyte ions can penetrate into the surface layer. The partition coefficients of cations and anions between the solution and the surface layer, which are related to their solubilities in the surface layer, may be different from unity.The electrostatic interaction depends on the ionic partition coefficients between the solution and the surface layer, and the relative permittivity of the surface layer, as well as on the membrane-fixed charges, the electrolyte concentration in the solution, and the surface layer thickness. It is shown, in particular, that even where the charge layer has no fixed charges, the electrostatic interaction force can be produced if the solubilities of cations and anions are different in the surface layer. 相似文献
5.
An asymptotic model is proposed for the flow pattern inside a droplet when a thin liquid layer is formed at its advancing nose; at small gap widths, so far as the substantial part of the flow inside the droplet is concerned, the interface may be regarded as a flat interface. Calculations are made using the classical potential theory. The problem of hydrodynamic interaction is brought to the investigation of an integral equation for the radial velocity a the flat interface. The equation is asymptotically solved for low and high viscosities in the droplet. For these cases, results are also reported about drag force. 相似文献
6.
The interaction energy-distance curves of fractionated and unfractionated homo- and copolymers were measured. The results were compared quantitatively with the HVO theory. It was found that only a small number of segments per tail are necessary to obtain stability. The experimental energy-distance curves for low molecular weights are described sufficiently well by the HVO theory, with exponentional distribution of tail sizes. For high molecular weights the exponential distribution cannot be considered as a reasonable assumption because the number of segments in the tails is very low.Polydisperse samples of PVA with different contents of acetate groups, and similar molecular weight, indicate an increasing extension of the adsorbed polymer layer with decreasing acetate content. 相似文献
7.
The interaction of ions (Na+, K+, Li+, Ca2+) with monolayers of phosphatidic acid alkyl esters (alkyl = methyl, ethyl,n-propyl,n-pentyl) were investigated at the air/water interface on Tris-HCl buffer, as well as on the electrolytes containing subphases.Qualitatively it can be stated that there are no considerable interactions between Na+ ions in the substrate and the head groups of phosphatidic acid esters in the monolayers. On the whole, the modification of the shape in the /a and v/a isotherms (
s
= film pressure, v
s
= film potential) of the homologous phosphatidic acid esters as a function of the length of the ester group on the subphase containing NaCl, KCl, and LiCl corresponds to that on Tris-HCl buffer without admixture of electrolytes.On the other hand the strength of interaction between Ca2+ ions and the homologous phosphatidic acid esters depends on the length of the ester group. The film-condensing effect of Ca2+ ions becomes smaller with increasing length of the ester group. 相似文献
8.
A model is proposed which explains the shape of the dielectric relaxation function at the glass transition of polymers. The model is based on the idea that the molecular mobility at the glass transition is controlled by intra- and intermolecular interaction. In addition, a specific model for the local chain dynamics in amorphous polymer systems is used. According to the scaling hypothesis of molecular dynamics the model relates the high frequency dependence of the dielectric loss curve to the local chain dynamics and the low frequency dependence to the intermolecular correlation. 相似文献
9.
E. Mileva 《Colloid and polymer science》1990,268(4):375-383
The hydrodynamic interaction of a solid particle and the boundary layer around a rising bubble is analyzed in the before-contact state (BCS) of a flotation act. The lagging of the particle behind the basic outer flow is accounted for. The forces acting on the particle are qualitatively examined. A new term is introduced in the force balance — the migration force. An expression for the collision efficiency is proposed that concerns a particle already entrained in the bubbles boundary layer. 相似文献
10.
Sequential anionic polymerisation routes have been used to prepare AB diblock copolymers, where A is either polystyrene or polydimethylsiloxane, and B is poly(2-vinylpyridine-1-oxide). The latter block, which is water-soluble, was obtained from the oxidation of poly(2-vinylpyridine) using peroxyacetic acid (giving 100% yield).The resultant diblock copolymers were characterised by gel-permeation chromatography, proton nuclear magnetic resonance and gravimetric microanalysis to give relative block lengths and polydispersity indices. For both types of block copolymersM
w
/M
n
values <1.25 could be readily obtained under carefully controlled conditions. 相似文献
11.
L. M. Gan S. C. Ng S. P. Ong C. H. Chew L. L. Koh 《Colloid and polymer science》1989,267(12):1087-1095
Dynamic and static light scattering techniques were used to study the droplet size and the interdroplet interaction of w/o microemulsions consisting of cetyltrimethyl-ammonium bromide (CTAB), hexyl carbitol, toluene, water and poly(ethylene glycol). The results were analyzed in terms of a hard-sphere model with a perturbation. For the microemulsions without polymer, their droplet sizes increased only slightly (R=10.1 to 11.0 nm) and the perturbation became more attractive as the molar ratio of H2O/CTAB was raised from 50 to 82. In contrast, an increase in polymer concentration or polymer molecular weight not only increased the droplet sizes but also changed the perturbation to become more repulsive. In addition, it is envisaged that the interactions between the cationic groups of CTAB and the ether linkages of the poly(ethylene glycol) may also enhance the rigidity of the interfaces, hence the stability of the microemulsions. 相似文献
12.
A study of the ternary polymer systems dimethyl formamide-ethyl acetate-polystyrene, chloroform-1,4 dioxane-polystyrene and tetrahydrofuran-chloroform-polystyrene was carried out by viscosity and light scattering at 298 K. A good correlation has been found between the excess intrinsic viscosity, unperturbed polymer dimensions, second virial coefficient and the excess Gibbs free energy by using a ternary interaction parameter, dependent on molecular weight. This modification enables the conversion between transport and equilibrium properties. 相似文献
13.
The electrostatic interaction pressure of charged surface layers is considered qualitatively and quantitatively. In the case of mutual penetration of the surface layers in addition to Maxwell stress and osmotic resp. hydrostatic pressure an isotropic stress on the fixed charges carrying molecules of the surface layers has to be taken into account. The derivation of the pressure-distance equations is given starting from both thermodynamic/electrostatic and hydrostatic/electrostatic principles. A possible biological significance of the additional stress is discussed emphasizing its role in modifying the structure of surface layer molecules.List of symbols
e
0
elementary charge
-
k
Boltzmann constant
-
n
i
concentration of theith ionic species in the bulk solution
-
P
hydrostatic pressure
-
P
hydrostatic pressure in the bulk volume (× )
-
P
h
integration constant, independent on ×:P
h
=P(h)
-
T
absolute temperature
-
Z
i
electrovalence of theith ionic species
-
thickness of the surface layer
-
,
0
relative and absolute permittivities
-
II(×)
osmotic pressure at position ×
-
II
osmotic pressure in the bulk solution (× )
-
osmotic pressure in the symmetry plane of interacting identical surface layers (electric field strength equals zero)
-
integration constant, independent on ×:
-
e
h
electrostatic component of the disjoining pressure
e
h
=
e
(h)
-
(×)
mobile charge density profile (cations and anions of the electrolyte)
-
(×)
fixed charge density profile
-
t(x)
total charge density profile (
t
= +)
-
1(x)
fixed charge density profile of one of the two surface layers (
1(×) 0 for 0×)
-
(×)
electric potential profile 相似文献
14.
T. Okubo 《Colloid and polymer science》1987,265(7):597-603
The ordered structures are observed directly by the metallurgical microscope for the heavy (specific gravity=1.50) and monodisperse polystyrene type spheres in sedimentation equilibrium and in the presence of neutral polymers, polyvinylalcohol (PVA), polyethyleneglycol (PEG), polyvinyl-pyrrolidone (PVP), hydroxypropylcellulose (HPC), and polyacrylamide (PAAm). The intersphere distances in the ordered lattices decrease by the addition of neutral polymer in the order, PVA < PEG < PVP < HPC < PAAm. These effects of neutral polymers are reasonably well-explained by the intersphere repulsion from the electrical double layer interaction, which is influenced by the polymer adsorption on the latex surface by the hydrophobic and/or dipole-dipole interactions. 相似文献
15.
J. Miñones O. Conde P. Díaz Fernández M. Casas Parada 《Colloid and polymer science》1991,269(9):916-922
Surface pressure-area isotherms (-A) of poly(L-alanine) (PA), poly(L-glutamic acid) (PG), and poly(L-arginine) (PArg) monolayers spread on substrates of varous pH values containing silicic acid were recorded and compared with those obtained on silica-free substrates. The compression curves of PA showed a pH-independent plateau region which was assumed to correspond to a monolayer to bilayer transition. The inflection observed in the -A curves of PG was attributed to the formation of loops made up of the terminal heads of the polymer and lying under the monolayer. Polysilicic acid interacted with the PArg films at pH 6; such films were more rigid and stable and had larger specific areas than those obtained in the absence of silica, which prompts the occurrence of an ionic interaction. The other two polyamino-acids did not interact with silicic acid at any pH value, so we may rule out the formation of hydrogen bonds between the silanol groups of polysilicic acid and the peptide or carboxyl groups of these amino acids. 相似文献
16.
The charge-transfer interaction of pyridinium salts with lysozyme and L-tryptophan has been investigated by visible absorption, circular dichroism and fluorescence spectroscopy. Four quaternized and substituted pyridinium salts were used as electron acceptors. L-tryptophan was used as a model compound of electron donor for the purpose of the comparison with lysozyme. The binding constants obtained from absorption and circular dichroism spectra were 2.0–13 M–1 and the sequence of the magnitude was found as EPCl(1-ethylpyridinium chloride) < MPCl(1-methylpyridinium chloride) < MNCl(1-methylnicotinamide chloride) < MNMCl(1-methyl-3-carbomethoxypyridinium chloride), which could be explained by the electron affinity of the pyridinium salt. The fluorescence spectra of lysozyme and L-tryptophan in the absence and presence of pyridinium salts were interpreted by Stern-Volmer plot. The static constants thus determined were in agreement with the binding constants obtained by other methods. 相似文献
17.
F. Reig C. Mestres I. Haro G. Valencia J. M. García Antón M. A. Alsina 《Colloid and polymer science》1989,267(2):139-144
The miscibility of phosphatidylserine, phosphatidylcholine, and cholesterol in monolayers were studied. The influence of sodium and calcium ions in this system was determined. The compression isotherms of mixed monolayers of the above cited three components spread on subphases containing opiate molecules are elucidated. Moreover, the penetration kinetics of opiate molecules in these mixed monolayers was also recorded. The results show that the presence of cholesterol always lowers the penetration of opioid molecules; this effect is weaken for meperidine, the most hydrophobic of the molecules assayed.Abreviations PS
phosphatidylserine
- PC
phosphatidylcholine
- PI
phosphatidylinositol
- Chol
cholesterol 相似文献
18.
19.
Structure transfer from a polymeric melt to the solid state. Part II: Dependence on molecular weight
Melt spinning experiments of polyethylene, using a high quenching rate have been carried out. Molecular weight has been varied. From measurements of the mechanical properties of the monofilaments produced it is concluded that melt history influences the solid state behavior. This is reflected in the hypothesis of a transference of knots, preexisting in the melt into the solid state. Measurements of the elastic recovery allow to offer an interpretation, in which this network of knots does not percolate, until a critical value of the molecular weightM
c knot105 is surpassed. The possible influence of these knots on the mobile entanglements is discussed.On leave from the Institut für Technische und Makromolekulare Chemie, Universität Hamburg, Hamburg, Germany. 相似文献
20.
Interaction between ethyl(hydroxyethyl)cellulose and sodium dodecyl sulphate in aqueous solution 总被引:2,自引:0,他引:2
Using sodium activity, viscosity, and cloudpoint measurements, it has been shown that sodium dodecyl sulphate (SDS) binds to ethyl(hydroxyethyl)cellulose in a cooperative manner. In the absence of salt the binding leads to an increase in the clouding temperature, but when a small amount of salt (0.01 molal) is present first a drastic decrease and then an equally drastic increase in the cloud point temperature is observed. The binding of SDS also initially leads to an increase in viscosity followed by a decreased viscosity at higher SDS concentrations. A molecular mechanism explaining the observed behavior is given. 相似文献