Chitosan is a promising environment friendly active polymer packaging material due to its biodegradability, exceptional film forming capacity, great mechanical strength, appropriate barrier property along with intrinsic antioxidant and antimicrobial features. Bifunctional reagent was used for producing water insoluble chitosan films. Biopolymeric films crosslinked by Genipin (Gp), which is a reagent of natural origin, should have high potential in food packaging. The influence of the ratio of functional groups in the chitosan-Gp system on film absorption in the visible and ultraviolet regions of the spectrum, sorption, physical, and mechanical properties of the films has been studied. The degree of chitosan crosslinking in the films obtained from solutions containing Gp was estimated using the experimental data on film swelling and water vapor sorption isotherms. It is demonstrated that crosslinking with genipin improves swelling, water resistance, and mechanical properties of the films.

The results ofthe sorption properties of cellulose acetate (CA) with different degrees of substitution (SD) are summarised. It has been shown that the sorption capacity of CA in water vapour decreases naturally with increasing content of acetate groups in monomeric units of cellulose ethers. The experimental isotherms are analysed according to the double sorption model. Hydrate numbers of hydroxyl and acetate groups were determined. The paired parameters of the Flory–Huggins interaction were calculated. It is shown that the decrease of the Langmuir component is due to the replacement of hydroxyl groups by ester groups, whose local sorption capacity by water vapour is lower than the sorption capacity of OH groups. In the area of high humidity, there is an increase in vacancy sizes due to plasticisation of the sorbents.

The sorption–diffusion characteristics of rigid-chain glassy polymers based on polyheteroarylenes (PHAs) have been studied in a wide interval of relative humidity and temperatures of thermal treatment of the polymer sorbents. Experimental data on water vapor sorption for polynaphthoyleneimidobenzimidazole (PNIB) and its copolymers with different chemical nature have been obtained. Water diffusion coefficients have been calculated, and parameters of their concentration and temperature dependences have been determined. It was found that water molecules sorbed by PNIB and its copolymers are strongly bounded. Water mobile and cluster states depend on the structure of macromolecules and thermal prehistory of polymer sorbents. It is shown that the translational coefficients of water diffusion for all PHAs are in the range from 10⁻⁹ to 10⁻⁸ cm²/s. The diffusion coefficients also increase slightly with temperature increasing, and their general dependence on temperature is satisfactorily described by the Arrhenius equation. The average activation energy of water diffusion varies from 24.3 to 25.9 kJ/mol. The hydrate numbers of rigid-chain PHAs functional groups have been determined. The above-mentioned results allow us to predict the sorption properties of heterocyclic macromolecular sorbents with complex chain architecture.

The degree of crystallinity of carbon fibers (CFs) of different manufacturers has been determined by means of the Raman scattering method. A gradient “core–shell” model for the CF structure has been suggested. The element composition of CFs has been determined by means of the X-ray electron probe analysis. It has been established that the CF includes oxygen-containing groups, the concentration of which varies from 2 to 4 wt %. A fibrillar structure of the CF shell has been identified via the methods of atomic force probe microscopy and transmission electron microscopy. Longitudinal and transverse sizes of fibrils have been determined. Using the method of low-temperature nitrogen adsorption, the specific surface area, porosity, and pore sizes of CFs have been determined. Isotherms of water vapor sorption by CF within the moisture range from 10 to 95 wt % have been obtained. It has been demonstrated that, for all the studied samples, the sorption isotherms can be approximated using the Dubinin–Radushkevich equation. The sorption capacity of water vapor by CFs has appeared to significantly exceed that of nitrogen, which was associated with the presence of oxygen-containing functional groups.

Isotherms of water-vapor sorption by aramid fibers and films of various nature were determined by static sorption methods. Structural and morphological characteristics of aramid fibers were investigated by the methods of transmission and scanning electron microscopy, X-ray structural analysis. It is shown that the studied industrial aramids are X-ray amorphous mesophases. The diffusion coefficients of water in aramids of various thermal prehistories have been determined. Greater interest is presented by the region of high humidity, where a rather sharp increase in the diffusion coefficients is observed for fibers and membrane films, which is associated with an increase in the segmental mobility of aramids and the onset of the process of devitrification of sorbents. The factor of complication of the transport paths during the transition from copolyamide membranes to fibers has been calculated. The sorption capacity of industrial aramid fibers in the entire range of water-vapor activity is significantly lower than the sorption capacity of films, membranes, and model sorbents. It is shown that paracrystalline mesophases act as “impermeable particles” in aramids. It is shown that absorbed water in polymers can exist in a nonassociated state or in the form of clusters. The number of water molecules included in the clusters has been determined.