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Permeability measurements for oxygen and nitrogen were carried out on a series of structurally similar polyimides in order to define structure/permeability relationships. The polyimides were prepared from 5,5′‐[2,2,2‐trifluoro‐1‐(trifluoromethyl) ethylidene] bis‐1,3‐isobenzofuranedione (6FDA) and a variety of substituted methylene dianilines and benzidines. A correlation between the diamine monomer structure and polymer permeability was found, particularly with diamine monomer variations at the ortho positions of the diamine relative to the amino moiety. These correlations were semilogarithmic, relative to the summation of the substituent volumes. Direct correlations were observed between the measured properties of polymer density and interchain d‐spacings and the oxygen permeability value of each of these polyimides. In addition, we observed that the calculated values of fractional free volume were related to oxygen permeability in a manner which enabled us to identity a polar component in the effects of these ortho substituents. © 1993 John Wiley & Sons, Inc.

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Poly [ 1 -(trimethylsilyl)propyne] (PTMSP) is a n unusual polyyne material which is optically clear, exhibits high solubility in nonpolar organic solvents, and good oxygen compatibility. By contrast, polyacetylene is black, insoluble, and is unstable in oxygen. The long term stability of PTMSP has been determined by a combination of thermal gravimetric analysis (TGA) and permeability test procedures under a number of different isothermal aging conditions. The use of commercial antioxidants at up to 2 weight percent improves the long term stability of PTMSP. The presence of the antioxidant has no effect on the surface fluorination of PTMSP. Testing of PTMSP films for over eight months shows no change in either permeability or selectivity in contrast to previously reported data.Puratronic grade purchased from Alfa Inc., was PolymerizationPolymerization of PTMSP was carried out in a dry box as follows: TaC15 (0.5 g, 1.4m moles) was dissolved in 100 ml of toluene. The mixture was stirred for 30 min at room temperature. To this catalyst solution was added TMSP (12 g lOOm moles). The mixture immediately turned dark brown and the solution solidified within 30 min. After 24 h the polymerization mixture was worked up by precipitation of the polymer in rapidly stirred excess hot methanol. The polymer was washed several times with hot Purchased from Petrarch Systems Inc., was refluxed over CaHz under a nitrogen purge for 24 h and methanol and then dried to a constant weight. A yield of >95 percent was typically achieved by this process.

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