We obtained binary polyelectrolyte complexes containing chitosan from Bombyx mori and collagen with a mass ratio of 10:1; 10:2, and 10:3. During the interaction between the macromolecules, due to the compensation of the positive charges of chitosan with the negative charges of collagen, the zeta potential of the solutions of polyelectrolyte complexes changed from +15.2 to +5.67 mV. We revealed the dependence of the size characteristics of the particles of polyelectrolyte complexes on time and the ratio of macromolecules. An examination of the morphology of the films of polyelectrolyte complexes demonstrated that in the evaluated chitosan/collagen mass ratios, non-spherical nanosized particles up to ≤ 60 nm form on the surface of the films. We evaluated the mechanism of formation of complexes by using Fourier-transform infrared spectroscopy and confirmed the findings with density functional theory and molecular dynamics. We found that the particle diameter is inversely proportional to the diffusion coefficient. The results show that the particles are almost uniformly distributed over the surface of the polymer matrix and have a unimodal character. We obtained reproducible results when using a chitosan/collagen mass ratio of 10:2 to dye natural silk. We found that the complexes contribute to increase the intensity and stability of colour relative to soap and friction.

Bombyx mori chitosan nanoparticles (ChS NPs) were obtained and the kinetic aspects of their size distribution depending on the degree of nonequilibrium of the synthesis by ionotropic gelation using sodium tripolyphosphate (TPP) were studied. The size of ChS NPs was greatly influenced by the ChS concentration, which varied from 0.5 to 10 mg/ml. The size of the NPs increased from 100 to 300 nm when the ChS concentration increased from 0.5 to 10 mg/ml and while maintaining all other parameters of the reaction. An increase in the ChS to-TPP ratio corresponded to a lower cross-linking density and thus ensured slower kinetics for NP formation alongside the formation of large chitosan/TPP aggregates. There was an almost threefold increase in the particle size when the pH of the medium increased from 3.8 to 4.7; thus, the size of ChS NPs depends on the pH of the solution. There was a slight agglomeration of NPs from 363 to 642 nm with an increase in the NP synthesis time from 4 to 24 h. According to calculations, the maximum interaction energy is 50.4 and 69.4 kcal/mol for deprotonated TPP (P3O105-); after adiabatic transfer of the proton, the value decreases to 32.9–33.5 kcal/mol. The maximum interaction energy is –12.8 kcal/mol for the initially protonated TPP (H4P3O10-).

The interaction of chitosan (ChS) and the Bombyx mori protein on different pH ranges was studied, and the fundamental possibility of obtaining complexes of ChS with the Bombyx mori protein was revealed. The for-mation of a polymolecular complex of protein with ChS in aqueous solutions was confirmed by the results of physico-chemical methods. It is shown that the ChS structure is characterized by a certain rigidity and ionogenicity. The results indicate the complexation of the pupae protein with ChS in 2% acetic acid in the range of pH = 4.8–6.7. The detected changes and shifts of the absorption bands in the IR spectra confirm the occurrence of the complex formation reaction between the molecules of ChS and protein at pH = 4.8–6.7, which is characterized by absorption bands in the IR spectra at 1641 cm–1, 1538 cm–1 and 1068 cm–1. Quan-tum-chemical DFT study of ChS complexes with amino acids (AAs) was carried out. The stability of com-plexes of ChS with AAs (ChS-AA) was shown except for the complex formed with histidine in the gas phase. The calculation results indicate the presence of a strong thermodynamic driving force in the complexation of ChS with AAs.

Using methylammonium lead iodide (MAPbI3) as an example, the process of complexation of molecular particles from solution at the initial stage of crystalli