Colloid science, investigations

FIG. 12.4 The domain within which most investigations of aqueous colloidal systems lie in terms of particle radii and 1 1 electrolyte concentration. The diagonal lines indicate the limits of the Hiickel and the Helmholtz-Smoluchowski equations. (Redrawn with permission from J. Th. G., Overbeek, Quantitative Interpretation of the Electrophoretic Velocity of Colloids. In Advances in Colloid Science, Vol. 3 (H. Mark and E. J. W. Verwey, Eds.), Wiley, New York, 1950.)... 

In recent years the investigation of polymer-surfactant interactions is a rapidly growing field of interest of modem colloid science [1-4], The mixtures and multilayer structures of polyelectrolytes and surfactants are widely used for industrial application to govern the wetting, adhesion, flotation processes and so on. 

Kinetic studies have been important in many areas of chemistry, but, to date, classic kinetic approaches have not played a major role in the area of colloidal science related to self-organisation of surfactants. Although micellar kinetics were investigated in some detail in the 1970s, related work involving other self-assembly systems, e.g., vesicles, lyotropic liquid-crystalline phases, have been limited. 

Because of the availability of these new methods, devices, and purer materials, it has become more feasible to carry on effective research with adequate surface-chemical control of gas and liquid adsorption, wetting, adhesion, emulsification, foaming, boundary friction, corrosion inhibition, heterogeneous catalysis, electrophoresis, electrode surface potentials, and a variety of other subjects of interest in the surface-chemical and allied fields of research. In view of the present situation, serious investigators should now be able to report results in the scientific literature which will have much more value than ever before. There is no excuse for any investigator s taking such inadequate care in controlling surface composition or surface-active contaminants as was common in over 50% of the research publications in surface and colloid science in the past. 

In this chapter I have attempted to show in a broad sense how the application of the basic principles of colloid science can be applied to develop our understanding of the various mechanisms involv in the stabilization of polymer latices. In the space availaUe, it was not possible to go into veiy specific details of the many systems that have been investigated nor to deal with nonaqueous polymer latices. The latter, however, have been discussed in the recent comprehensive book by Barrett (1975). The literature on polymer colloids appears to be growing exponentially and to the authors of the many excellent papers which I have not quoted, I offer my sincere apologies. 

The heterogenous nature of emulsion polymerization processes, and the stepwise mechanisms involved add complications to the understanding of the kinetics. Despite the investigations conducted in emulsion polymerization over the last few decades, the scientific representation of these complex processes remains incomplete. With recent advances in fundamental chemistry and colloid science, model uncertainties have diminished. 

Although this material is not directly related to colloid science, the authors have decided to include it, because in the experimental investigation of various colloidal phenomena discussed in this book one frequently encounters the task of measuring the amount of surfactant in different phases... 

Along with the methods based on investigation of the scattering of light by disperse system as a whole, there are also methods based on the scattering (the diffraction) of light on individual particles. One of such methods, ultramicroscopy, played an important role in the development of colloid science. Dark field optical systems, ultramicroscopes, and dark field condensers, such as those utilized in optical microscopes for side illumination,... 

In the case of films with high stability the overcoming of potential barrier does not result in a rupture of film, but leads to another metastable state corresponding to the primary minimum (Fig. VII-10, point B). This results in the formation of a rather stable, very thin Newtonian black films [15]. The investigation of the nature of stability of black films is one of the central problems in colloid science nevertheless, at present there is no commonly accepted opinion concerning the nature of forces that are responsible for high stability of black films (see Chapter VIII). 

Many disperse systems with solid continuous phase are the common subjects for studies in such areas of science as material science, physics of materials, physics of metals and others. This is related to the existing great variety of such systems. Obviously, their properties (among which mechanical ones are of primary importance) are significantly different from those of systems with liquid dispersion medium. At the same time, the investigation of processes leading to the formation of such systems and their interactions with ambient media constitute direct subjects of colloid science. 

This book covers major areas of modern Colloid and Surface Science (in some countries also referred to as Colloid Chemistry) which is a broad area at the intersection of Chemistry, Physics, Biology and Material Science investigating the disperse state of matter and surface phenomena in disperse systems. The book arises of and summarizes the progress made at the Colloid Chemistry Division of the Chemistry Department of Lomonosov Moscow State University (MSU) over many years of scientific, pedagogical and methodological work. 

Colloids are extremely important to both commerce and life. The Information Age of the late twentieth century nurtured many advancements allowing more detailed investigation of colloidal materials. Lasers and computers, of course, have greatly affected all areas of science. In return, colloids play a major role in the semiconductor industry. Silica-alumina sols polish silicon wafers that go into diode lasers, memory chips, and microprocessors. Everyone takes advantage of colloidal suspensions, especially since the human body contains so many with its cells, proteins, and DNA. As society pushes to make so many things smaller, more functional, and more efficient, colloid science will become increasingly pertinent to technological developments, see also Solution Chemistry. 

This section provides brief explanations for the most important terms that may be encountered in a study of the fundamental principles, experimental investigations and industrial applications of colloid science and silica chemistry. 

Colloids are of considerable industrial importance and have intrinsic scientific interest. Generally they consist of a sol system, i.e., submicrometer-sized solid particles dispersed in a liquid phase that can polymerize into a continuous three-dimensional network called a gel. In particular, colloidal sols of oxides and hydroxides, either as such or as precursor dispersions, have numerous and wide-ranging applications in catalysis, coatings, optics, microelectronics, and ceramics and other composite materials. The importance of investigations on such systems is unquestioned, and many articles on this field are issued every month in the several periodicals on colloid science and materials science. Among these colloidal systems, silicon and aluminum oxopolymers, which transfo m into an oxide... 

In the 200 years since Thomas Graham founded the discipline of colloid science, a vast number of terms have come to be associated with colloid and interface science and, in particular, with the sub-discipline of surfactant science. In addition to the fundamental science, there is a great diversity of occurrences and properties of surfactants in industry and in everyday life. This chapter provides brief explanations for the most important terms that may be encountered in a stndy of the fundamental principles, experimental investigations, and petrolenm industry-related applications of surfactant science. Specific literature eitations are given when the sources for further information are partieularly useful or unique. For terms drawn from fundamental colloid and interface seienee, much reliance was placed on the recommendations of the lUPAC Commission on Colloid and Surface Chemistry [I], For more comprehensive dictionaries and glossaries of terms in colloid and interface science, see references [2-7]. 

Petrus (Peter) Josephus Wilhelmus Debye (1884-1966). .. was a Dutch physicist and physical chemist, who worked in the fields of quantum physics, X-ray analysis, microwave spectroscopy, and electrochemistry. Colloid science benefits from his contribution to X-ray and light scattering (in particular for aggregates— Eq. (4.39)— and concentrated suspensions—Eq. (2.24)), his work on electrolyte solutions (Debye-Hiickel theory), as well as his remarks to electrophoresis and his research on polymers. He was awarded the Nobel Prize in Chemistry in 1936 for his work on molecular structure through his investigations on dipole moments and the diffraction of X-rays and electrons in gases . 

Albert Einstein (1879-1955). .. was a German-bom theoretical physicist who is mainly renowned for his special theory of relativity and its extension to the general theory of relativity. In addition to this, he worked on statistical mechanics and quantum theory and investigated the thermal properties of light. At the beginning of his scientific career he also set important landmarks for colloid science. This applies particularly to his explanation of Brownian motion, but is also valid for the calculation of suspension viscosity as well as his theory of critical opalescence. In 1921, he was given the Nobel Prize in Physics Tor his services to theoretical physics, and especially for his discovery of the law of the photoelectric effect . 

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