The role of dipole—dipole interactions in the formation of the structure of amorphous Teflon AF2400 and complexation of acetone with perfluorodioxolane rings

Abstract

FTIR spectroscopy investigation have shown that the contact of acetone with the film of Teflon AF2400 led to changes in the intensities of some absoption bands of the polymer and to the splitting of the stretching vibration band νC=O of acetone. The theoretical vibration spectrum of a model of AF2400 repeat unit was obtained. It is in good agreement with the experimental spectrum of the film of this polymer. The bands, whose intensities change during the contact of the AF2400 film with acetone, belong to the stretching and deformation vibrations of the C-F bond of the dioxolane ring as a whole. Structural, energy, and electron characteristics of a complex of acetone with the perfluorodioxolane ring were calculated by the B3LYP/6-31G(d) method. The dipole-dipole character of interaction of acetone with the repeat unit of AF2400 with the involvement of the whole dioxolane ring was demonstrated. The polarizabilies of the C=O bonds in acetone and the C-F bonds in the dioxolane ring of the polymer are substantially changed, which is in good agreement with the experimental IR spectrum of the AF2400 film that had been in the contact with acetone. The results of quantum chemical and molecular dynamics calculations testify the orthogonal-block structure of the chains in AF2400, which explains great stiffness and a large free volume of this polymer.