Colloid properties particle size

Latex particles can be used for micromanipulation by taking into account that some of their colloidal properties (particle size and dielectric behavior) can be affected for instance imder the action of a laser beam or an electric field. 

The significant characteristics of colloids are particle size and shape, scattering of radiation, and kinetic properties. 

The colloidal characteristics of A -alkylacrylamide- or Af-alkylmethacrylamide-based particles are temperature related. In fact, the swelling ability, charge density, charge distribution, hydrophilic-hydrophobic balance, hydration and dehydration properties, particle size, surface polarity, colloidal stability, water content, turbidity, and electrokinetic and rheological properties are indis-cemibly temperature dependent. Such polymer particles can be used as a stimuli-responsive model for the investigation of colloidal properties and for theoretical studies. 

These polymers possess the characteristics of a true latex concerning colloidal stability, particle size uniformity, him forming properties, etc. However, the fact that they are not manufactured from monomers but by direct emulsification of already formed polymers makes them free of (pcHentiaiiy toxic) unreactcd monomers, and they can hence be used in the body without toxicity hazards (124.125). 

Rowell and co-workers [62-64] have developed an electrophoretic fingerprint to uniquely characterize the properties of charged colloidal particles. They present contour diagrams of the electrophoretic mobility as a function of the suspension pH and specific conductance, pX. These fingerprints illustrate anomalies and specific characteristics of the charged colloidal surface. A more sophisticated electroacoustic measurement provides the particle size distribution and potential in a polydisperse suspension. Not limited to dilute suspensions, in this experiment, one characterizes the sonic waves generated by the motion of particles in an alternating electric field. O Brien and co-workers have an excellent review of this technique [65]. 

The colloidal state of matter is distinguished by a certain range of particle size, as a consequence of which certain characteristic properties become apparent. 

The defined size ranges and limits are somewhat arbitrary since there are no specific boundaries between the categories. The transition of size ranges, either from molecular dispersions to colloids or from colloids to coarse dispersions, is very gradual. For example, an emulsion may exhibit colloidal properties, and yet the average droplet size may be larger than 1 pm. This is due to the fact that most disperse systems are heterogeneous with respect to their particle size [1-2]. 

One of the most obvious properties of a disperse system is the vast interfacial area that exists between the dispersed phase and the dispersion medium [48-50]. When considering the surface and interfacial properties of the dispersed particles, two factors must be taken into account the first relates to an increase in the surface free energy as the particle size is reduced and the specific surface increased the second deals with the presence of an electrical charge on the particle surface. This section covers the basic theoretical concepts related to interfacial phenomena and the characteristics of colloids that are fundamental to an understanding of the behavior of any disperse systems having larger dispersed phases. 

A state of subdivision of matter with a particle size between 10"7 and 10 5 cm (1 nm to 100 nm). The properties of colloids lie between those of true solutions and coarse suspensions. 

Particles of a size of less than 2 turn are of particular interest in Process Engineering because of their large specific surface and colloidal properties, as discussed in Section 5.2. The diffusive velocities of such particles are significant in comparison with their settling velocities. Provided that the particles scatter light, dynamic light scattering techniques, such as photon correlation spectroscopy (PCS), may be used to provide information about particle diffusion. 

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