Surface force lyophilic system

Large-scale, systematic research in colloid chemistry began in the Soviet Union in the 1920s. Among the prominent chemists in this field are Dumansky (lyophilic colloids), Peskov (stable disperse systems). Rebinder (surface-active substances, physicochemical mechanics), Zhukov (electro-surface phenomena), and Deryagin (surface forces). Fundamental interdisciplinary research was carried out by Frumkin, Balandin, Boreskov, Chmutov, Laskorin, and others. The outstanding schools in the former Soviet Union in the field of adsorption developed under the leadership of Dubinin, A. V. Kiselev, and Neimark. 

The presence of an essentially similar liquid medium and of surfactant adsorption influences the magnitude and nature of the surface forces and may result in weakened cohesion in the contacts by two to three orders of magnitude. In a lyophilized, highly concentrated system in which the particles are brought into mechanical contact, this is revealed through lower resistance to deformation, x, and results in a plasticizing of the system (see Chapters 2 and 3). When the disperse phase concentration is low, lyophilization leads to the preservation of the colloidal stability of a free-disperse system, that is, the resistance of the system to coagulation (see Chapter 4). 

Latexes constitute a subgroup of colloid systems known as lyophobic sol. Sometimes they are called polymer colloids. The stability of these colloids is determined by the balance between attractive and repulsive forces affecting two particles as they approach one another. Stability is conferred on these latexes by electrostatic forces, which arise because of the counterion clouds surrounding the particles. Other forces of an enthalpic or entropic nature arise when the lyophilic molecules on the surfaces of the latexes interact on close approach. These can be overcome by evaporation of the water, heating, freezing, or by chemically modifying the surfactant, such as by acidification. 

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