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Novel polyimides (PIs) based on the isomeric mixture of diethyltoluenediamine and 6FDA, BPDA, BTDA, ODPA, and BPADA dianhydrides are synthesized using a one-stage technique. The synthesized polymers possess high thermal stability and molecular weight, increased glass transition points T g > 400°C (except for PI with BPADA), and good film-forming properties. The polymers are soluble in chloroform, NMP, DMAA, and DMSO. The investigation of the gas transport of the synthesized polymers shows that the polyimides with 6FDA and BPDA dianhydride fragments can be assigned to the class of highly permeable polyimides (the oxygen permeability coefficients are 82 and 28 Barrer, respectively). The gas transport parameters of the synthesized polymers turn out to be comparableto those for the polyimides based on 2,4,6-trimethyl-m-phenylenediamine studied previously.

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The transport of oxygen, nitrogen, and hydrocarbons C1–C4 in polyimides based on 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and biphenyl-3,3',4,4'-tetracarboxylic acid dianhydride (BPDA) and diethyl toluene diamine (DETDA) has been studied. The dependences of the diffusion coefficient on the diffusant effective diameter and the solubility coefficients on the Lennard–Jones potential of pair interaction have been considered. It is shown that the diffusion coefficients of butane are out of the linear dependence of the logarithm of the diffusion coefficient on the square of the effective diameter of the diffusant, which may indicate the plasticization of polymers with butane at a pressure of 1 atm. The permeability of mixtures of gases O2–N2 (29 : 71 v/v) and CO2–CH4 (62 : 38 v/v) has been studied. There are no significant differences in the gas separation parameters in comparison with the experiment for individual gases; however, for a mixture of CO2–CH4, a slight increase in the separation factor has been found as compared to the ideal selectivity. The data on the measurement of sorption isotherms and solubility coefficients O2, N2, and CH4 are also presented in the article. Gas solubility coefficients have been found to be close to the values obtained indirectly as P/D.