Influence of the ascorbic acid isoform on the sol–gel synthesis kinetics and properties of silicon–chitosan-containing glycerohydrogel plates

Abstract

Glycerohydrogel thin-film plates based on chitosan l-(d-)ascorbate and poly(vinyl alcohol) were obtained by means of template sol–gel synthesis with silicon tetraglycerolate as a biocompatible precursor. The rheokinetics of the sol–gel process is considered, the deformation and strength characteristics of the material were evaluated. The gelation time during plate formation has been established to decrease with increasing the template concentration and temperature. Chitosan d-ascorbate has been found to retard gelation. Stress–strain curves characteristic of soft elastic materials were recorded for our samples of silicon-containing glycerohydrogel plates. At rupture, the material shows some characteristic signs of macroscopic plasticity. The maximum achievable values of the physicomechanical parameters depend on the template/precursor ratio. With an increase in this ratio, the tensile strength increases, whereas the concentration dependences of the relative elongation at break and Young’s modulus show an extreme character. The plates based on chitosan D-ascorbate had higher mechanical strength and elasticity under uniaxial tension and a lower value of Young’s modulus as compared to those based on chitosan l-ascorbate. The regularities obtained are discussed from the standpoint of the influence of the ascorbic acid isoform on the conformational features of chitosan macromolecules and their supramolecular ordering in the glycerohydrogel system.