Spherical polystyrene latex

Finally, Giddings et al. [174] described an S-FFF device in which the channel was coiled along the internal wall of the centrifuge basket (see Fig. 14A,B and also Fig. 15). The basic theoretical and experimental aspects of S-FFF were discussed and the fractionation of a series of monodisperse spherical polystyrene latexes was demonstrated [174]. The principle of a rotor for S-FFF capable of being applied at low centrifugal fields corresponding to speeds up to 6000 rpm is shown in Fig. 15 [175]. 

Lee and Lightfoot [229] developed the theoretical basis of Fl-FFF. This theory has been confirmed by numerous works on the fractionation of model systems, including monodisperse spherical polystyrene latexes and a number of proteins [41,228,229,240], some polydextrans [229], viruses [241], and other spherical particles and macromolecules [242,243]. 

Monodisper.se, spherical polystyrene latex particles in aqueous su.spension are available commercially in sizes ranging from 0.088 to about 2 m. Relative standard deviations in panicle size are usually less than 0% and sometimes less than 1%. The suspensions are manufactured industrially by emulsion polymerization. Monodisperse polyvinylioluene particles of somewhat larger diameter, up to 3.5 im. are also available. The properties of these systems are reviewed by Mercer (1973). 

Monosized spherical polystyrene latex particles of diameter 1.73 yarn and polyvinylpyridine of molecular weight equal to 589,000 were employed, for which C is equal to 3.06 g/L. The experiments were carried out at pH 3.0 and 25°C. 

In Fig. 6, we illustrate some different ways that the core-shell topology could be varied for silica and gold. So far we have considered the two normal core-shell structures. We now focus on the third example the assembly of Au Si02 nanoparticles onto spherical polystyrene latex colloids. The resulting spheres are also essentially different to continuous metal shells grown on colloid templates, which have been reported by Halas and colleagues [17] and by van Blaaderen and coworkers [18]. Such continuous shells display optical properties associated with resonances of the whole shell, and are therefore extremely sensitive to both core size and shell thickness, while in the system presented here... 

Cryo-TEM images of spherical polystyrene latex particles stabilized by 10 wt% Laponite ciystallites (run 2 in Table 2). In b, the arrows point to a few Laponite platelets seen edge-on on the surface of the polystyrene particle. 

Calibration Particle Size Distributions Using Spherical Polystyrene Latex Suspension via Spray Atomization and Diffusion Drying. 

The penetration of spherical polystyrene latex particles was higher than that for M. chelone, a rod-shaped bacterium, in tests carried out on N95 respirators, although the two particles are of comparable aerodynamic size (Qian et al. 1998). 

The particles studied [22,23] were monodisperse, surfactant-free spherical polystyrene latex particles with sulfate groups on the surface. When these groups are fuUy ionized in water, the particles have a surface charge density of around 8 /xC cm , equivalent to 1 sulfate group per 2 nm. Unless otherwise stated, the particle diameter was 2.6 /u.m. 

Monodisperse spheres are not only uniquely easy to characterize, but also very rarely encountered. Polymerization under carefully controlled conditions allows the preparation of the polystyrene latex shown in Figure 1.8. Latexes of this sort are used as standards for the size calibration of optical and electron micrographs (also see Section 1.5a.3). However, in the majority of colloidal systems, the particles are neither spherical nor monodisperse, but it is often useful to define convenient effective linear dimensions that are representative of the sizes and shapes of the particles. There are many ways of doing this, and whether they are appropriate or not depends on the use of such dimensions in practice. There are excellent books devoted to this topic (see, for example, Allen 1990) and, therefore, we consider only a few examples here for the purpose of illustration. 

Many papers report the fractionation of polystyrene latexes or mixtures thereof, as such commonly available spherical latex standards are an ideal system to test FFF setups or evaluations (for an example, see [362,401]). Recent coupling of Fl-FFF to MALLS enables a very high precision in particle size determinations. One example is shown in Fig. 31, where two Duke standard latex batches of a nominal size of 100 nm were investigated by Fl-FFF/M ALLS, underlining both separation power and resolution. Using traditional techniques such as photon correlation spectroscopy (PCS) and classic Fl-FFF detection, these samples seem to be identical. However, with Fl-FFF/MALLS, the batches could be separated as two discrete size distributions with a peak size that differed by 3 nm. However, it is not stated if a precise temperature control was maintained so that, critically considered, the observed differences could also have their origin in slight temperature... 

FIGURE 25.25 SEM image of the cross-section of a silica layer with spherical macropores resulting from the thermal degradation of polystyrene latex. 

The role of surface viscosity and elasticity on the motion of a solid particle trapped in a thin film, at an interface, or at a membrane of a spherical vesicle has been recently investigated in References 604 and 605. The theoretical results ° have been applied to process the experimental data for the drag coefficient of polystyrene latex particles moving throughout the membrane of a giant lipid vesicle. Thus, the interfacial viscosity of membranes has been determined. 

Indeed, much higher levels of conductance fluctuations were reported for electrolytes that contain polystyrene latex suspensions (21) or micellar colloids (22). Fluctuations were shown to depend on concentration, characteristic size, and the charge of colloid particles. For uncharged nonconductive spherical particles that occupy volume fraction F of the total sample volume... 

Figure 1.3 Electron micrographs of colloidal materials in which three, two, and one dimensions lie in the colloid range (bars indicate 1/am) (a) spherical particles of monodisperse polystyrene latex, (b) packed spherical particles of polystyrene latex, (c) fibres of chrysotile asbestos, (d) thin plates of kaolinite.

A priori, latices formed by the polymerization of dispersions of a water-insoluble monomer in aqueous media are expected to exhibit a wide distribution of particle sizes. In the 1950 s, chemists at the Dow Chemical Company discovered that a batch of polystyrene latex consisted of spherical particles that were uniform in diameter. At the time, this was considered a laboratory curiosity. Nowadays, monodisperse latices have found a wide variety of applications [74]. An early application was in pregnancy testing kits. Other uses are in diagnostic tests for various ailments and for the presence of illegal drugs. These microparticles are available in a variety of colors and with various functionalities along the polymer chains. They may be prepared as porous particles and as... 

Synthesis via colloid crystallization allows the pore size to be controlled in the range of nanometers to micrometers. Using the colloidal mixmre of silica and polystyrene latex as a precursor, it is possible to obtain spherical shaped porous silica particles, that can be used as a catalyst in chromatography and as the material for controlling the release of dmgs, as weU as in microelectronics... 

N.J. Marston, B. Vincent, N.G. Wright, The synthesis of spherical rutile titanium dioxide particles and their interaction with polystyrene latex particles of opposite charge. Prog. Colloid Polym. Sci. 1998, 109, 278-282. 

Polystyrene latex (PSL) particle suspensions are common calibration materials for aerosol research and aerosol instmmentation and the National Institute of Standards and Technology (NIST) has several spherical nanoscale standard reference materials available, including SRM1963a (dp =100 nm) and SRM1964 (dp = 60 nm) that are suitable for calibration of aerosol... 

For a brush on a flat surface, the attached chain is confined to a cylindrical volume of radius D/2 and height A. If the individual chains of the brush are attached to a spherical core (as is the case with nanoparticles), then the volume accessible to each chain increases and the polymer chains have an increased freedom to move laterally resulting in a smaller thickness A. This is schematically illustrated in Fig. 2.28 which shows the difference between particles with high surface curvature (Fig. 2.28 (a)) and that for a surface with low surface curvature (Fig. 2.28 (b)). The curvature effect was illustrated for PEG and poloxamer block copolymers using polystyrene latex particles with different sizes. An increase in the layer thickness with increasing particle radius was observed. 

However, many numerical solutions of the PB have become available now which can be exploited for estimating the validity of the approximate models. In these calculations, pioneered by Hoskin and Levine [21,44], one uses the finite-difference method and the PB equation is formulated in the bispherical coordinate system. The advantage of this orthogonal coordinate system is that the boundary conditions at the sphere surfaces can be accurately expressed. This coordinate system (with more mesh points) was subsequently used by Camie et al. [45], who performed calculations of the interaction force for two spherical particles in a 1-1 electrolyte. The authors proved that the electrostatic fields distribution within the particles exerted a negligible effect on interaction force characterized by 8 < 5 (e.g., polystyrene latex particles). 

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