Influence of polyvinyl alcohol on the rheology and morphology of an l -cysteine-AgNO 3 supramolecular system
- PDF / 1,055,561 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 69 Downloads / 202 Views
1443
Influence of polyvinyl alcohol on the rheology and morphology of an L-cysteine—AgNO3 supramolecular system* D. V. Vishnevetskii, A. N. Adamyan, A. I. Ivanova, S. D. Khizhnyak, and P. M. Pakhomov Tver State University, 33 ul. Zhelyabova, 170100 Tver, Russian Federation. Fax: +7 (482 2) 32 1274. E-mail: [email protected] A good compatibility of an aqueous solution of polyvinyl alcohol (PVA) of various concentrations with a cysteine—silver solution (CSS) was revealed. It was found by viscosimetry that an increase in the polymer concentration leads to an increase in the viscosity. This effect for hydrogels is more substantial than that for solutions. The self-assembly processes in the systems were studied by UV spectroscopy and dynamic light scattering. The morphology of hydrogels and solutions of the CSS—PVA system was studied by scanning electron microscopy. The formation of a single regular spatial network was found for the hydrogels, whereas two fluctuation networks were observed for the solutions. The network is formed from aggregates, which are particles of interacting CSS and polymer molecules. A possible mechanism was proposed for self-assembly in the systems. The possibilities of practical application of the new systems are discussed. Key words: L-cysteine, silver nitrate, polyvinyl alcohol, supramolecular structures, selfassembly, gelation, porosity.
Investigations of low-concentrated systems based on compounds with the biologically active properties evoke increasing interest. Low-concentrated gels,1—9 i.e., systems in which the content of the disperse phase is very low compared to the dispersion medium, play a special role among these objects. There are few known such systems. At the same time, it is important to study them for understanding the appearance of the spatial self-assembly of dissolved substances. This phenomenon is nontrivial and insufficiently studied for dilute solutions (at a concentration of 0.1% and lower). These systems often manifest a phenomenon of thixotropy along with plasticity and the ability to retain the shape. Thixotropy is the ability of a substance to decrease the viscosity (to rarefy) under the mechanical action and to increase the viscosity (to thickened) in the quiescent state. The study of solution structuring is of interest for the modification of the already existing technologies and, in particular, biotechnologies, since it is known that gels can act as a structural basis of biomedical remedies and can serve as an active matrix for biologically active compounds enhancing their effect. The hydrogel based on L-cysteine and AgNO3 was synthesized.10—12 The gel is formed on mixing low-concentrated (0.01%) aqueous solutions of L-cysteine and * Based on the materials of the XXI Mendeleev Congress on General and Applied Chemistry (September 9—13, 2019, St. Petersburg, Russia).
some silver salts and upon the introduction of gelation initiators (aqueous solutions of salts of various metals). It is remarkable that the starting components are biologically active compounds. The
Data Loading...
