Perfluoroalkylene oxide derivatives as potential elastomer precursors

Abstract

The synthesis of octadecafluoro-3,9-dloxa-1,11- bis(3-methoxycarbonyl phenyl) undecane from hexafluoroglutaryl fluoride, via the intermediate octadecafluoro- 1,11-diido-3,9-dioxaundecane has been examined. Each stage of this sequence proceeds in poor yield, and no substantial improvement could be obtained by variation of conditions. The physical properties of the product lead to handling difficulties, and an attempt to derive a polymer from the system failed. A synthesis of difluoromalonyl chloride from perfluorocyolohexa-1,4-diene is described. Difluoromalonyl fluoride could not be obtained pure, either by fluorination of the chloride, or by direct oxidation of the diene. The addition reaction of hexafluoropropene epoxide with hexafluoroglutaryl fluoride, catalysed by caesium fluoride, provides a route to a mixture of fluorinated bifunctional ethers. By appropriate choice of reaction conditions, the isomeric distribution in the products maybe restricted; a mechanism Is suggested to account for the observed product distribution. Separation and purification of the reaction products provided a series of ether-containing bifunctlonal compounds, which on reduction yielded a corresponding series of ether diols. Polycondensation of the diols obtained as above with isophthal .oyl chloride gave a series of polyesters, which were compared with analogous polyesters derived from other systems. The thermal stability of polyesters having an ether link situated β to the eater group Is significantly lower than that of polyesters lacking this feature, but no simple relation was found between structure and the activation energy for degradation. The glass transition temperatures of non-ether containing polyesters correlate moderately well with predicted values. A knowledge of the glass temperatures of ether containing polyesters allows the calculation of the glass temperature of the hypothetical high molecular weight homopolymer of hexafluoropropene epoxide; a value of ca.-57ºC was obtained.