ИСТИНА

In the middle of the 20th century, Scott turned his attention to some unsolved problems of chemical thermodynamics, including the problem of solutions of fluorocarbon compounds. The behavior of fluorocarbon FC and hydrocarbon HC mixtures is often in contradiction with the predictions of the theory of regular solutions that are based on their solubility parameters. Later, similar relationships were found for solute–polymer systems. Recently, Inverse Gas Chromatography has been used to study infinite dilution sorption in several polymers with different fluorine concentrations: the tetrafluoroethylene– perfluoromethyl vinyl ether copolymer, and tetrafluoroethylene-perfluoromethoxidioxole copolymer, a partially fluorinated hyperbranched Si-containing polymer (HBP), dendrimer 7.5G, and the ‘hydrocarbon’ rubber poly(pentenamer) (PPM). Thermodynamic parameters of sorption of fluoro-containing derivatives of toluene (toluene, p-fluorotoluene, 2,3,4,5,6-pentafluorotoluene, and octafluorotoluene), namely, solubility coefficients, excess partial molar enthalpies and entropies, Flory-Huggins parameters etc., have been determined. In this report one makes an attempt from two points of view to embrace the experimental results having been obtained previously: (i) effect of content of the fluorine in the compounds under consideration and (ii) effect of physical state of the polymer (glassy – below glass transition temperature (Tg) – and rubbery (>Tg). The following conclusions can be made: 1) hydrocarbon solutes are characterized by low solubility coefficients in fluorinated rubbers and rather high one in PPM, whereas in dendrimer, HBP, and linear polysiloxanes they have intermediate values of S. Opposite behavior is observed for fluorocarbon solutes. 2) solubility coefficients of the solutes in glassy state polymers are always higher than those in rubbery state polymers. 3) Excess enthalpies of solute–rubber systems reflect intermolecular interactions between the solute molecule and the polymer. For solute-glassy polymer system, one needs additionally to take into consideration glassy nature of the polymer. In the systems containing C-F and C-H bonds intermolecular interactions are unfavorable (endothermic mixing), whereas in systems only with C-F or C-H bonds, they are favorable (exothermic mixing). Similar behavior is observed for Flory–Huggins parameter.