We have synthesized a polymeric quaternary ammonium salt of β-methacryloylethyl-Ndimethyl(allyl)ammonium bromide (β-MAEDAB) based on reaction of N,Ndimethylaminoethylmethacrylate with allyl bromide. We have developed a water-soluble polymeric composition based on the polyquaternary salt of β-MAEDAB combined with glycerol for treatment of natural fibers (cotton and wool) and leather (cowhide and goatskin). We have studied the physical and chemical properties of aqueous solutions of the polymeric composition and have determined the optimal formula for the composition to use for finishing fibers and leathers. We have studied the physical and mechanical properties of natural fibers and leathers modified by the polymeric composition based on a polyquaternary salt.Today serious problems are encountered in the technology of production of natural materials made from local raw material (cotton and wool fibers, natural leather) which are reflected in the quality of both the materials and articles made from them.During the production process, cotton and wool fibers are subjected to many mechanical loads causing stretching, bending, breaking, twisting, compression, etc., which leads to their mechanical and chemical degradation and poorer properties. Modification of the fibers with solutions of polymeric compositions makes it possible to improve both their processability into textile material and the physical, mechanical, performance, and technological parameters of this material.In connection with features of the climate conditions and preservation methods, leather obtained from raw material prepared in Uzbekistan is quite susceptible to poor break and has poor grain strength. Accumulation of fat in the dermis, especially at the boundary between the reticular layer and the papillary layer, and the presence of voids lead to its loosening, which results in lower strength of the hides, and leathers produced from them do not meet the requirements for leather used for apparel. As we know, poor break leads to reduced grading of the leather and loss of up to 8%-10% of their useful area.In order to improve the quality of leathers, synthetic polymers based on polyacrylates (derivatives of acrylic and methacrylic acids and their esters) are used as fillers for leather intermediates [1][2][3][4]. Treatment of leathers with polymers promotes an increase in their wear resistance, more even properties over the surface topography, prevention of poor break, and improvement in the physical and mechanical parameters.In the IR spectrum of collagen modified by the polymeric salt, we observed bending vibrations of the -NH 2 groups in the 15.4 m -1 typical of collagen. The shift of the absorption band for the >C=O group from 17.2 to 17.45 m -1 may be evidence for interaction between the quaternary nitrogen of the polymeric salt and the carbonyl group of the collagen, with formation of intermolecular chemical bonds, which is supported by the adhesion properties of the polymeric salt relative to natural leather. In particular, adhesion of goatskin ...