Some Physical Characteristics of Colloids

What these imply is that, at the minimum, we need to be aware of the complexities in representing quantitatively particle sizes, shapes, and the extent of their variations. It is also important to be aware of some of the standard experimental tools that are available for this purpose. In this section and the next, we consider some of these items. For convenience, we restrict ourselves primarily to some of the most common methods and techniques. 

7 Some of the microstructures produced by the self-association behavior of diblock copolymer solutions. The figure illustrates the (a) spherical, (b) cylindrical, and (c) lamellar structures (among others) that are possible in such solutions. Each diblock polymer chain consists of strings of white beads (representing one type of homopolymer) and strings of black beads (representing the second type of homopolymer). (Redrawn from A. Yu. Grosberg and A. Khokhlov, Statistical Physics of Macromolecules, AIP Press, New York, 1994.) 

8 Electron micrograph of cross-linked monodisperse polystyrene latex particles. The latex is a commercial product (d = 0.500 jun) sold as a calibration standard. (Photograph courtesy of R. S. Daniel and L. X. Oakford, California State Polytechnic University, Pomona, CA.) 

I Characterizing Variations in Shape Particles with a High Degree of Symmetry Many solid particles are not actually spherical, but are characterized by a high degree of symmetry like a sphere and are often approximated as spheres. For example, a polyhedron approximates a sphere more and more closely as the number of its faces increases. 

Another method of characterizing irregular particles consists of reporting the diameter of a circle that projects the same cross section as the particle in question. This is done by 

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