Colloidal Domain

Colloids have been defined classically as systems involving characteristic length scales ranging from a few to a few thousand nanometers. Until a few decades ago, this range of dimensions has attracted relatively little scientific interest. The two far ends of our perception of space, the subatomic elementary particles on one side and the universe with its galaxies at the other, have been much more appealing to scientists. 

Engineering Materials science Medical sciences Environmental 

FIG U RE 1.1 Length scales relevant for varions scientific disciplines. 

FIGURE 1.2 Biological systems belonging to the colloidal domain. 

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Evans D F and Wennerstrom H 1994 The Colloidal Domain—Where Physics, Chemistry, Biology, and Technology Meet (New York VCH) pp 12-16... 

Fennel Evans D and Wennerstrdm FI 1994 The Colloidal Domain (New York VCFI)... 

The broader field of colloid science continues to attract overviews, the most recent being a book entitled The Colloidal Domain, Where Physics, Chemistry am Biology Meet (Evans and Wennestrdm 1999). 

Evans, D.F. and Wenneslrdm, H. (1999) The Colloidal Domain, Where Physics, Chemistry and Biology Meet (Wiley-VCH, Weinheim). 

Evans DF, Wennerstrom H (1999) In The Colloidal Domain, second Edition. Wiley-VCH, New York... 

Figure 10.11 As the aggregate number n increases, so the fraction of the added surfactant that goes into the micelle (as y ) varies more steeply with total concentration of surfactant monomer (as V). The critical micelle concentration (CMC) is the midpoint of the region over which the concentration of the micelle changes (Reproduced by permission of Wiley Interscience, from The Colloidal Domain by D. Fennell Evans and Hakan Wennerstrom)...

The Colloidal Domain Where Physics, Chemistry, Biology, and Technology Meet (second edition) by D. Fennell Evans and Hakan Wennerstrom, Wiley, New York, 1999, is a superb book which satisfactorily demonstrates the interdisciplinary nature of the topic. Its biological examples are particularly good. They also present a nice discussion on pp. 602-603 of how colloid science contributed to the growth of several, disparate strands of science. 

Evans, D. F. and Wennerstrom, H. (1994). The Colloidal Domain Where Physics, Chemistry, Biology and Technology Meet. VCH Publishers, New York. 

In this group of disperse systems we will focus on particles, which could be solid, liquid or gaseous, dispersed in a liquid medium. The particle size may be a few nanometres up to a few micrometres. Above this size the chemical nature of the particles rapidly becomes unimportant and the hydrodynamic interactions, particle shape and geometry dominate the flow. This is also our starting point for particles within the colloidal domain although we will see that interparticle forces are of great importance. 

Evans D F, Wennerstrom H K (1999) The colloidal domain where physics, chemistry, biology, and technology meet. WUey-VCH, New York... 

Evans, D. F., and Wennerstrom, H., The Colloidal Domain Where Physics, Chemistry, Biology, and Technology Meet, VCH Publishers, New York, 1994. (Undergraduate and graduate levels. A textbook on colloids covering many of the topics discussed in the present book, but presented almost exclusively from the point of view of surfactant systems and self-assembly.)... 

D. F. Evans and H. Wennerstrom, The Colloidal Domain, where Physics, Chemistry, Biology, and Technology meet. (VCH, New York/Weinheim, Cambridge, 1994). 

Numerical calculations can be carried out on the basis of Eqs. (70)-(74), and to show the influence of the image forces on the disjoining pressure between two plates, we will compare these results with the frequently used expression in Eq. (75). We have still to adhere to the approximations accepted in the text, and, first of all, the bulk electrolyte concentration c0 = 1 mmol/L will be chosen. For this concentration the Bierrum (or plasma) parameter is n — ky q = 0.04, and, as a consequence, for characteristic interparticle distances of a colloid domain the relationship a = Kr /x is much smaller than one. This allows to simplify our equations sufficiently leading to the final expression for the disjoining pressure, where the dominant role plays the self-image interaction... 

Refs. [i] Evans ED, Wennerstrom H (1999) The colloidal domain. Wiley-VCH, New York, pp 217 [ii] Hunter RJ (2004) Foundations of colloid science, 2nd edn. Oxford University Press, Oxford, pp 539 [iii] Hamaker HC (1937) Physics 4 1058 Morrison ID, Ross S (2002) Colloidal dispersions. Suspensions, emulsions, and foams. Wiley Interscience, New York, pp 355... 

Simulation techniques suitable for the description of phenomena at each length-scale are now relatively well established Monte Carlo (MC) and Molecular Dynamics (MD) methods at the molecular length-scale, various mesoscopic simulation methods such as Dissipative Particle Dynamics (Groot and Warren, 1997), Brownian Dynamics, or Lattice Boltzmann in the colloidal domain, Computational Fluid Dynamics at the continuum length-scale, and sequential-modular or equation-based methods at the unit operation/process-systems level. 

In order to formulate the desired relationships in a useful way, one needs to know about the intermediate inhomogeneous domain. This domain is referred to as the mesoscopic domain. Of particular relevance are domain sizes between 10 nanometers and millimeters, which are referred to as the colloidal domain. The physics that is relevant to this intermediate domain size is called mesoscopic physics, and science relevant to this length scale is classically referred to as colloid science. The physics and the physical chemistry regarding the mesoscopic domain acts as a bridge for formulating relationships between properties on a molecular scale and those at a macroscopic scale. 

D. Fennell Evans is the director of the Center for Interfacial Engineering and professor of chemical engineering and materials science at the University of Miimesota. He is the author of more than 180 publications on self-assembly processes in water and nonaqueous solvents, microemulsions, diffusion in liquids and micellar solutions, and characterization of surfaces using scanning probe techniques. He has published two textbooks. The Colloidal Domain and The Fundamentals of Interfacial Engineering. 

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