Аннотация:Metathesis poly(5-perfluorobutyl-2-norbornene) has been synthesized for the first time with a high yield of 85–98% and a variable cis/trans ratio of double bonds over first- and third-generation Grubbs’ Ru catalysts in solution. The conditions for preparing the parent monomer 5-perfluorobutyl-2-norbornene with a yield of up to 98% have been selected. The study of the gas separation properties of the final polymer showed that the introduction of a perfluorobutyl substituent into the repeating unit of polynorbornene increases the permeability for noncondensable gases due to an increase in their diffusion coefficients. The ideal selectivity for gas pairs containing methane increases or remains almost unchanged as a result of an increase in the difference between the solubility coefficients of these gases. The reasons for the observed changes in the gas separation and other properties of polynorbornene can be associated with a rigid conformation and weak interaction of fluoroalkyl substituents, which affects the free volume of the polymer and the energy of interaction of macromolecules with each other and with penetrant molecules. The study expands the understanding of gas separation and other properties of the class of fluorinated polynorbornenes.