IX Международная студенческая научная конференция Студенческий научный форум - 2017

Emulsion is a very complex but at the same time most interesting object for studies in modern colloid chemistry. Although much work is devoted to this topic [1-5], the decision of emulsions stabilization remains an actual connected with their theoretical and practical meaning. Recently, attention is drawn to the fact that emulsions stabilized by polymer-surfactant systems are existing potential new direction to microencapsulate different volatile substances such as perfume or fragrance, for a wide range of products for the home and personal care, cosmetics, food, and pharmaceuticals.

In the presented work complexes of the water-soluble polymer Polysterensulphonate (PSS) and cationic surfactant dodecyltrimethylammonium bromide (DOTAB) were prepared and their stabilizing effect on oil-water emulsions investigated. The PSS-DOTAB complexes were prepared by mixing the solutions of the individual compounds at concentration ratio 0,1; 0,2; 0,3; 0,4; 0,5. Solutions of the complexes were used 24 h after mixing. The interfacial tension at the tetradecane-water interface was measured by Drop profile analysis tensiometry (PAT-1, SINTERFACE), and DLS and zeta-potential measurements were performed at 25°C using NanoZS90 system (Malvern Instruments). Emulsions were prepared at room temperature by ultrasound at a mixing time of 2 minute. The obtained emulsions were poured into 14 ml calibration tubes and then their emulsifying efficiency was studied by observation of emulsion stability every 30 minute. The principle of observation was based on the determination of the volume of the separated oil phase. The size distribution of emulsion droplets was measured directly after emulsion formation by using a Zetasizer (Malvern), and repeated over 10 days.

The zeta potential measurements showed that the combination of DOTAB and PSS at the interface resulted in charge reversal at the interface.

The mean drop size shows that within optimum concentration ratios the emulsion stability is growing. The results after 3 days show that there was no coalescence in the emulsion, i.e. a negligible change of the mean droplet size was observed. Figures 2 show the size distribution by intensity of emulsion particles with concentration ratio of composition PSS/DoTAB from n=0,1 to n=0,5. It was established that optimal concentration ratio are 0,25-0,5, where emulsion is very stable. We observed these emulsion stability during year period.

Figure 2. Mean drop size of the dispersed phase of an oil-water emulsion, in dependence on concentration of the stabilizing system DOTAB/PSS

So, it was established that there is an optimum ratio for the surfactant-anion-active polymer mixture at which the emulsion stability reaches a maximum. As it was proposed very recently in [6] this optimum ratio, probably, correspond to the stoichiometric composition of surfactant-polymer complexes. Any further increase in the surfactants concentration above this optimum (0,25-0,5) leads to a decrease in the emulsion stability.

So, the results presented and their interpretation represent a development in the understanding and decision problems of emulsion formation and stability for scientifically-substantiated approach to their usage for important technological processes like a microencapsulation of a variety of volatile components, such as perfumes, or flavors, in a wide range of applications in home and personal care products, cosmetics, foods, and pharmaceuticals.

References

1 Adsorption of Polymer−Surfactant Mixtures at the Oil−WaterInterface. Ian M. Tucker, Jordan T. Petkov, Craig Jones, Jeffrey Penfold, Robert K. Thomas,Sarah E. Rogers, Ann E. Terry, Richard K. Heenan, and Isabelle Grillo. Langmuir 2012, 28, 14974−14982.

2 Howe, A. M.; Pitt, A. R. Rheology and stability of oil-in-water nanoemulsions stabilized by anionic surfactant and gelatin. (1) addition of nonionic, cationic and ethoxylated-cationic cosurfactants. Adv. Colloid Interface Sci. 2008, 144, 24.

3 Murray, B. S. Rheological properties of protein films.Curr.Opin.Colloid Interface Sci. 2011, 16, 27.

4Becher, P. Emulsions, Theory and Practice; American Chemical Society: Washington, DC, 2001.

5Sjoblom, J., Ed. Emulsions and emulsion stability. Surfactant Science Series; Taylor and Francis: UK, 2005; Vol. 132.

6 B. Mutaliyeva, G. Madybekova, S. Aidarova, A. Sharipova, A. Lyubchyk, O. Lygina, S. Lyubchik. Journal “Scientific Israel-Technological advantages” Vol.15, 2, 2013, p.9-15.

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