Name of Excellence: Control of Foam and Emulsion Properties by Surfactants, Polymers and Particles
Author: Prof. Nikolai Denkov, DSc., Department of Chemical Engineering
Research domain: Physical Chemistry
| Nikolai Denkov, DSc. is a Professor at the Faculty of Chemistry and Pharmacy, Head of the Department of Chemical Engineering. Visiting researcher in Japan, France, and USA. Published 125 articles, incl. 16 reviews and book chapters, cited over 4500 times. He presented 81 invited lectures and seminars worldwide, and led more than 30 projects with international companies (Unilever, BASF, Rhodia, Saint Gobain). In 2010 he received the highest national award “Pythagoras” for scientific achievements.
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| Prof. Nikolai Denkov, DSc. |
In many chemical, food and pharmaceutical technologies one has to disperse one phase inside another phase, in the form of small solid particles, drops or bubbles. Foams (dispersions of gas bubbles in liquid or solid matrix), emulsions (drops of one liquid in another liquid) and suspensions (solid particles in liquid medium) are all representing such “disperse systems”. Well known examples from our daily life are the cosmetic emulsions (creams) and foams, pharmaceutical emulsions and suspensions, paints and coatings, many food products, solid foams for insulation of buildings, etc. A major technological problem in the generation and application of these disperse systems is to choose appropriate components called “surfactants” which cover the surface of the dispersed particles and thus stabilize them.
In recent years, using physico-chemical approaches, we have shown how one could select appropriate surfactants and other additives (polymers, solid nano-particles) which can stabilize the disperse systems and, in addition, could modify their properties into desired direction. For example, one could modify on demand the size of the dispersed particles and the stability, visual appearance and fl owing properties of the overall disperse system. New natural surfactants from plant extracts were found to have unique and useful properties. The observed phenomena were described theoretically and, on this basis, new combinations of surfactants were proposed.
The scientific results were described in 21 original articles and 3 extensive reviews in highly respected international journals. These studies were funded by several international companies (Unilever, BASF, Saint Gobain) which use already the obtained results in their product lines. Two international patents were filed.
Schematic presentation of air bubbles, dispersed in water and stabilized by surfactant molecules (left), surfactant-polymer mixtures (center) of solid particles (right)
Photograph of a porous material obtained after drying of aqueous foam, stabilized by solid particles (left). Image obtained at high magnification with electron microscope shows the pores in this material, which replicate the structure of the original wet foam from which this porous material was obtained after drying. Such porous materials find applications as thermal and noise insulation, and as fi lters or supports for catalysts