Latex particle deposition

As the latex particles deposit, a certain amount of soap will be co-deposited and become buried in the film. The conductivity of the film, other factors being constant, will increase with concentration of ions and water. 

Figure 7.8 Interference patterns produced by passing a laser beam through a thin layer of polymer latex particles deposited on a microscope slide (a) highly ordered layer showing Laue pattern, (b) disordered layer showing a speckle pattern which twinkles if the particles are mobile. The light intensity from a given area then fluctuates because of the Brownian motion of the particles.

Figure 2.4 DOTM images showing 6.4 im latex particle deposition above the critical flux (images a-d) and removal below the critical flux (images e, f). Images (a-d) were taken after 3, 5, 17 and 30 min, respectively, of filtration with 15Lm h (1 Lm h =...

From surfactant molecules it is known that the repeated vertical dipping of a substrate through a floating monolayer of these molecules leads to the formation of an LB multilayer on the substrate. In principle, the same procedure should also allow the preparation of multilayers of latex particles. In Figure 8b, the preparation of a particle bilayer is schematically indicated multiple repetition should result in the formation of an LB multilayer of particles. However, if one tries to realize this concept, one immediately gets into difficulties, because the contact of the particles with the underlying substrate is very poor, and the already deposited particle layer tends to detach from the surface when the substrate is dipped into... 

Polymerization in microemulsions allows the synthesis of ultrafine latex particles in the size range of 5 to 50 nm with a narrow size distribution [33], The deposition of an ordered monolayer of such spheres is known to be increasingly difficult as the diameter of such particles decreases [34], Vigorous Brownian motion and capillary effects create a state of disorder in the system that is difficult... 

Figure 3. Illustration depicting the physical form of latex protective garment material and cement or solvent dipped protective garment material and showing how a latex is deposited as colloidal particles whereas the cement dipped materials are deposited as molecular layers...

Polystyrene latex particles were coagulated by the addition of Ba(N03)2. The number of dispersed particles deposited onto a planar polystyrene surface was determined 15 min after the addition of salt by optical microscopy. The light microscope does not permit the aggregation of the deposited particles to be determined subsequent examination by the electron microscope gives this information. Clint et al. obtained the following results ... 

The coagulum deposited on the reactor surfaces may be the result of polymerization in large monomer drops or a separate monomer layer, or it may be the result of polymerization of the monomer in the vapor space above the latex or a surface polymerization on the walls and roof of the reactor. Polymerization in the vapor space of the reactor will form solid polymer in the form of particles which may stick to the reactor surfaces or fall into the latex in the later case, these particles serve as nuclei for the formation of coagulum. Polymerization of monomer on the reactor surfaces will form solid particles that become swollen with monomer and grow by flocculation of the latex particles. The surface polymerization can be related to the smoothness of the reactor surface the smoother the surface, the lesser the tendency for surface polymerization and formation of coagulum. 

Hull and Kitchener (2) measured the rate of deposition of 0.3- an-diameter polystyrene latex particles onto a rotating disk coated with a film of polyvinyl formaldehyde. In electrolytes of high ionic strength (where the double-layer repulsion is negligible), they found close agreement between experiments and the prediction of Levich s boundary-layer analysis (Eq. 3]), indicating that a diffusion boundary layer exists and that its thickness is large compared to the domain of van der Waais and hydrodynamic interactions. These are neces-... 

Clint el al. (4) measured the rate of deposition of 0.43-gm-diameter polystyrene latex particles onto a rotating disk coated with a polystyrene film in Ba(N03)s solutions of three different ionic strengths. Results are reported ia Table II. Also reported in this table are the surface potentials of the disk which are needed to force agreement between predicted and observed rates. Speculations 1 and 2 again refer to approach at constant surface potential or charge, respectively, when the potential is small enough to linearize the Poisson-Boltzmann equation. However, when the... 

Abstract. An overview of the synthesis and applications of microgels and coreshell particles is provided, with emphasis on work originating from the author s laboratory. Microgels, which are cross-linked polymer latex particles, can be used for selective uptake of ions or polymers, or the controlled release of various compounds. Various methods for the synthesis of core-shell particles are described such as interfacial polymerization, layer-by-layer deposition, colloidosomes , internal phase separation, and silica shells. The release kinetics for controlled (sustained or triggered) release purposes is discussed. 

The gold nanoparticle/polyelectrolyte coated latex particles are then conjugated with biotin molecules through a layer of biotinylated poly(allylamine hydrochloride) that is deposited on the particle surface before biotin binding. Fluorescein isothiocyanate labled anti-biotin immunoglobulin (FITC-anti-biotin IgG)... 

Figure 14.26. Laboratory experiments of the deposition and release of latex particles (0.308- m diameter) in 20-cm columns of glass beads. (0.4-mm diameter) at a flow rate of 0.136 cm s and a temperature of 22°C. (From Hahn and O Melia, personal communication, 1994.) (a) Typical breakthrough curve for deposition and reentrainment. Particles are deposited at / = 0.1 M KCl in phase 1 (0-34 min), eluted with 0.1 M KCl in phase 2 (34-58 min), and eluted with deionized water in phase 3 (58-90 min). Particles deposited in the secondary well are released at low ionic strength, (b) Breakthrough curve for deposition at very high divalent salt concentration (0.2 M CaCla) in phase 1 (0-32 min), elution at the same salt concentration in phase 2 (32-56 min), and elution with deionized water in phase 3 (56-90 min). Particles deposited in the primary well are not released at low ionic strength.

Figure 3.3 Deposits of 1,3-jum polystyrene latex particles on an 8.7- tm glass fiber mounled normal to an aero.sol flow and exposed for increasing periods of time. The air velocity was 13.8 cm/sec, and the particle concentration wa.s about 1000 cm . Photos by C, Billings (1966). The principal mechanism of deposition wa.s probably direct interception. Fracial-like structures develop as the pcirticles deposit.

Figure 3.13 CompEirison of experiment and theory for the deposition of monodisperse latex particles on a free-slanding wafer 4 in. in diameter. The air mainstream velocity normal to the wafer was 30 cm/sec, typical of microelectronics clean room operations. The diffu-sion equation wa.s solved numerically using calculated velocity and temperature distributions. The curves show that a small increase in surface temperature eHeelivcly suppresses deposition over a wide intermediate particle size range. Larger particles deposit by sedimentation smaller ones break through the thermal barrier by Brownian diffusion. (After Ye et aL, 1991.)...

Since physical parameters were held constant in these experiments, the theoretical single collector efficiency, r/(p, c)theor, is constant at 0.00256. The experimental attachment efficiency, a(p, c)exp, however, varies from 0.014 to 0.94, depending on the chemical composition of the solution. In the presence of a high concentration of Ca2+, the attachment coefficient approaches 1. This means that, in the absence of a repulsive chemical interaction, the mass-transport rale as calculated with Eq. 4 successfully describes the performance of these laboratory columns. At low ionic strength (pNa = 3.0), the sticking coefficient is reduced to a value of 0.014 by repulsive chemical interactions (presumably primarily electrostatic) between the suspended latex particles and the stationary glass collectors. Only 1.4% of the contacts produced by mass transport lead to attachment and deposition of the latex particles from the suspension. 

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