Study of the influence of the composition and pH of the solution on the structure and morphology of particle dispersions of a (bio)polyelectrolyte complex between chitosan and gelatin

Abstract

The work studied the formation and structure of (bio)PEC in mixtures of dilute chitosan and gelatin solutions at different pH and ratios of polymers and their ionized groups of z. Using the turbidimetry method for the chitosan and gelatin mixtures, it was found that stable scattering particles of (bio)PEC are formed in the pH range from 5 to 6.4 and with a polymer ratio above 1:5 (z = 0.29). The electrostatic interaction in the (bio)PEC structures was confirmed by ATR-FTIR spectroscopy. It was shown that during the formation of (bio)PEC in mixtures with pH = 5.5, a strong shift of the corresponding absorption bands relative to the initial polymers is observed. Studying the complexation and structure of these particles using the dynamic light scattering method of mixtures at pH = 3, the associative-dissipative character of the polymers interaction with the formation of soluble and unstable (bio)PEC dispersions was determined. It was observed that in mixtures with a pH = 5.5, the interaction becomes associative, which is accompanied by the formation of a (bio)PEC coacervate microphase at polymer ratios from 1:10 to 1:30 (in the z range from 0.58 to 1.73, respectively). Analysis of the structural properties of the coacervate microphase of (bio)PEC using dynamic light scattering and optical microscopy methods showed that with an increase in the proportion of an oppositely charged component of z ≥ 1, the isotropy of the polyelectrolyte binding process increases, which leads to suppression of the formation of loose heterogeneous coacervate particles of (bio)PEC.

Graphical Abstract