ИСТИНА

Polymer compositions containing polyelectrolyte complex of chitosan and polyacrylic acid and elastomeric latex, have been synthesized in aqueous media. The latex of the ternary copolymer of butylacrylate, methylmethacrylate and methacrylic acid (50:45:5) was used. Compositions including different ratios (10-90 wt.%) of polyelectrolyte complex and latex were investigated. The thin films with the thickness of 40-50 μm were prepared from aqueous formic acid (3.5 wt.%) solutions. Structure of the polymer compositions obtained was studied by means of differential scanning calorimetry (DSC), selective etching and electron microscopy. It was found that the compositions are heterogeneous systems composed of elastomer and polyelectrolyte complex phases with the strong electrostatic interaction on the interface. Using the selective etching of the compositions by 5% solution of formic acid and also by chloroform, it was established that in the region of compositions containing less than 50 wt.% of the chitosan - polyacrylic acid complex, the continuous phase is the elastomer. In the compositions containing more than 50 wt.% of the chitosan - polyacrylic acid complex, the polyelectrolyte complex is the continuous phase. Mechanical properties of the air-dried films prepared from the compositions were studied as well. The films containing less than 50 wt.% of chitosan - polyacrylic acid complex had a high elasticity, typical for elastomers. The films containing more than 50 wt.% of chitosan - polyacrylic acid complex had the mechanical characteristics, typical for polymers in a glassy state. The phase inversion phenomenon peculiar to heterogeneous polymeric systems was observed when the content of chitosan - polyacrylic acid complex in polymer compositions approximated 50 wt.%. Sorption and moisture exchange properties of the polymer compositions were also studied. It was shown that the increase of chitosan - polyacrylic acid polyelectrolyte complex content is accompanied by the increase of the ability of the compositions to sorb water vapors. Vapor permeability, hygroscopicity and moisture return of the polymer compositions were revealed to have the same tendencies. The compositions with the content of the chitosan - polyacrylic acid complex less than 50 wt.% are of particular interest. These compositions possessed a rather good elasticity as well as the high vapor permeability. Thus, this study has demonstrated promising use of the chitosan - polyacrylic acid polyelectrolyte complex as a hydrophilic modifier to elastomers with the aim to improve performance attributes of polymeric materials. At the same time the addition of elastomers to chitosan - polyacrylic acid polyelectrolyte complexes seems to be effective in significant improvement of their physico-mechanical characteristics at the low moisture content.