Colloid-polymer surface layers

Radeva, T., Petkanchin, 1., and Varogui, R., Electrical and hydrodynamic properties of colloid-polymer surface layers investigated by electro-optics, Langmuir, 9, 170, 1993. 

Application of Electro-optics To Investigate the Electrical and Hydrodynamic Properties of Colloid—Polymer Surface Layers... 

Charge neutralization, polymeric flocculation effect, 4-5 Colloid-polymer surface layers, electrical and hydrodynamic properties investigated with electro-optics, 121-135 Colloid stability, 161 Colloidal particles, polymer-induced attraction, 97... 

The second part is devoted to adsorption of polyelectrolytes at interfaces and to flocculation and stabilization of particles in adsorbing polymer solutions. A recent theory of the electrostatic adsorption barrier, some typical experimental results, and new approaches for studying the kinetics of polyelectrolyte adsorption are presented in the first chapter of this part. In the following chapters, results are collected on the electrical and hydrodynamic properties of colloid-polyelectrolyte surface layers, giving information on the structure of adsorbed layers and their influence on the interactions between colloidal particles examples and mechanisms are analyzed of polyelectrolyte-induced stabilization and fragmentation of colloidal aggregates ... 

Surface layer dissociation behavior, in polymer colloids, 20 381-383 Surface layer impregnation, hydrothermal technology for, 14 105, 106t, 107t Surface layers, IR spectra of, 24 110 Surface micromachining in MEMS, 22 260 of MEMS devices, 26 964 Surface modification adsorbents, 1 585... 

Vincent, B. (1990). The calculation of depletion layer thickness as a function of bulk polymer concentration. Colloids and Surfaces, 50, 241-249. 

In general, A and B subchains in an AB- or an ABA-type block copolymer have different solubilities or affinities for a solvent or other polymers. Therefore, it is expected that a block copolymer is surface-active when dissolved in a suitable solvent or mixed in polymer melts108. This property of block copolymers is now utilized to stabilize or flocculate colloidal dispersions. Blocks A, which are insoluble in a given solvent, are anchored in an insoluble polymer particle, and blocks B, which are soluble in the solvent, form a surface layer around the particle. 

H. Ohshima, Diffuse double layer interaction between two spherical particles with constant surface charge density in an electrolyte solution, Colloid Polymer Sci. 263, 158-163 (1975). 

Up to date, besides the SFA, several non-interferometric techniques have been developed for direct measurements of surface forces between solid surfaces. The most popular and widespread is atomic force microscopy, AFM [14]. This technique has been refined for surface forces measurements by introducing the colloidal probe technique [15,16], The AFM colloidal probe method is, compared to the SFA, rapid and allows for considerable flexibility with respect to the used substrates, taken into account that there is no requirement for the surfaces to be neither transparent, nor atomically smooth over macroscopic areas. However, it suffers an inherent drawback as compared to the SFA It is not possible to determine the absolute distance between the surfaces, which is a serious limitation, especially in studies of soft interfaces, such as, e.g., polymer adsorption layers. Another interesting surface forces technique that deserves attention is measurement and analysis of surface and interaction forces (MASIF), developed by Parker [17]. This technique allows measurement of interaction between two macroscopic surfaces and uses a bimorph as a force sensor. In analogy to the AFM, this technique allows for rapid measurements and expands flexibility with respect to substrate choice however, it fails if the absolute distance resolution is required. 

One of the most important parameters in the S-E theory is the rate coefficient for radical entry. When a water-soluble initiator such as potassium persulfate (KPS) is used in emulsion polymerization, the initiating free radicals are generated entirely in the aqueous phase. Since the polymerization proceeds exclusively inside the polymer particles, the free radical activity must be transferred from the aqueous phase into the interiors of the polymer particles, which are the major loci of polymerization. Radical entry is defined as the transfer of free radical activity from the aqueous phase into the interiors of the polymer particles, whatever the mechanism is. It is beheved that the radical entry event consists of several chemical and physical steps. In order for an initiator-derived radical to enter a particle, it must first become hydrophobic by the addition of several monomer units in the aqueous phase. The hydrophobic ohgomer radical produced in this way arrives at the surface of a polymer particle by molecular diffusion. It can then diffuse (enter) into the polymer particle, or its radical activity can be transferred into the polymer particle via a propagation reaction at its penetrated active site with monomer in the particle surface layer, while it stays adsorbed on the particle surface. A number of entry models have been proposed (1) the surfactant displacement model (2) the colhsional model (3) the diffusion-controlled model (4) the colloidal entry model, and (5) the propagation-controlled model. The dependence of each entry model on particle diameter is shown in Table 1 [12]. 

The Pti samples (182) were prepared as colloids, protected by a PVP polymer film. Layer statistics according to the NMR layer model (Eqs. 28-30) for samples with x = 0,0.2, and 0.8 are shown in Fig. 63. The metal/ polymer films were loaded into glass tubes and closed with simple stoppers. The NMR spectrum and spin lattice relaxation times of the pure platinum polymer-protected particles are practically the same as those in clean-surface oxide-supported catalysts of similar dispersion. This comparison implies that the interaction of the polymer with the surface platinums is weak and/or restricted to a small number of sites. The spectrum predicted by using the layer distribution from Fig. 63 and the Gaussians from Fig. 48 show s qualitative agreement w ith the observed spectrum for x = 0 (Fig. 64a). 

The polyolefin melt is forced through an annular slot 3 of extrusion head 2 and is blown out into a hose. A solution of Cl that is easily volatile in PI is fed onto the site over the mandrel. The Cl solution dissolved in the varnish based on PVB, CEVA or cellulose acetobutyrate is forced to the surface of a diaphragm Table 2.11. The varnish is poured over the inner surface of the rising hose so as to avoid contact between the lower edge of the annular flow of varnish and the Cl layer. The varnish contacts the colloidal solution of polyolefine with Cl formed in the hose surface layer. Above the solidification line A-A the colloidal solution decomposes into phases and a jelly-like layer is formed. Just in this layer the inhibiting liquid is enclosed in the polymer matrix pores that are thermodynamically compatible with the varnish. The varnish diffuses into the pores and, on setting, forms on the inner hose surface an inhibited varnish coat embedded in the porous layer. 

Thus, adsorption of small amounts of these surfactants can be monitored conveniently by SAXS because in the case of PS particles the main scattering intensity arises from the surface layer. In consequence, the scattering intensity of PS-particles covered by surfactant molecules strongly increases compared to the uncovered particles. Therefore PS latexes present ideal model systems for studying the adsorption of surfactants and polymers on colloidal particles from solution [53]. 

Freshly formed polymer films can adhere to each other. The application of a thin layer of colloidal silica prevents the twro polymer surface from meeting. 

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