Conditioning of Fluorine Containing Polyimides. 1. Effect of Exposure to High Pressure Carbon Dioxide on Permeability

Abstract

This paper discusses the effect of penetrant-induced conditioning on the gas transport properties of four fluorine- containing polyimide isomers. The effects of substitution of bulky groups within the dianhydride residue of the polyimide and isomerism of the diamine residue on the penetrant-induced hysteresis of CO2 permeability were investigated. The CO2 permeability in the polyimide films that had been conditioned with carbon dioxide at 60 atm are compared to those in the untreated films. Exposure of the polyimides to CO2 at 60 atm resulted in 4.5- to 10-fold increases in the permeability of CO2 relative to unconditioned films. The permeability enhancement was a result of increases in both the solubility and diffusivity following conditioning. There was also a surprising maximum in the permeability at intermediate pressures in conditioned samples of two of the polyimides. The permeability of CO2 in the conditioned polymers initially increased with decreasing pressure, exhibited a maximum value at approximately 30 atm, and decreased in permeability at low pressures.

Atomistic models of three fluorinated polyimides in the amorphous state

“…They play a crucial role in the simultaneous counting of different radiations in dosimetry measurements,12 as well as in preparing the optical waveguides in optical engineering 10. Their gas separation properties are also well known 3–5, 14–27. Indeed, the fluorine linkages are thought to disrupt effective packing and increase free volume in the polymer matrices, which tends to enhance the permeability of gas molecules.…”

Impact of H+ ion beam irradiation on Matrimid®. II. Evolution in gas transport properties

“…3). As ion fluence was 2 , irradiation resulted in increases in permeances for all gases studied. Since smaller molecules exhibited larger increases in permeances, there were simultaneous increases in permselectivities for several gas pairs.…”

“…1 To be commercially feasible, four important factors, i.e., permeability, permselectivity, stability at the operating conditions, and processibility, must be considered in selection of membrane materials. 2,3 There have been numerous studies of the relationship between polymer chemical structure and gas transport properties, and have led to general rules of thumb that allowed tailoring of polymers with improved gas permeation properties. For example, introduction of bulky groups within the polymer backbone, which can hinder both segmental mobility and intersegmental packing, results in simultaneous increases in permeability and permselectivity.…”

“…[4][5][6][7][8] In addition, reorganization of the fractional free volume (FFV) of a polymer can result in significant changes in gas transport properties. 1,2 While considerable progress has been made in synthesis of polymers with improved permeabilities and permselectivities, new polymers appear to be approaching a new upper bound limit of transport behavior as demonstrated by Robeson. 9 Moreover, polymers are typically limited to applications at fairly low temperature and in inert environments.…”

Interrelation between phase state and gas permeation in polysulfone/polyimide blend membranes

“…5,6,12,18,19 PIs, on the other hand, are thermally stable polymers with excellent mechanical properties and good correlation between permeability and selectivity, but with high cost and low CO 2 plasticization pressure. 7,20 Taking into account the complementary features of PSF and PI, PSF/PI blends have been used 21 and shown to have a miscibility window. In this article we investigate PSF/PI blends using calorimetry, rheology, X-ray scattering, and gas permeation in an attempt to correlate blend phase state and gas permeation.…”