Gas permeability and hydrocarbon solubility of poly[1-phenyl-2-[p-(triisopropylsilyl)phenyl]acetylene]

The effects of film thickness, physical aging, and methanol conditioning on the solubility and transport properties of glassy poly[1-phenyl-2- [p-(tri isopropylsilyl) phenyl] acetylene] are reported at 35 degrees C. In general , the gas permeability coefficients are very high, and this polymer is more permeable to larger hydrocarbons (e.g., C3H8 and C4H10) than to light gase s such as H-2. The gas permeability and solubility coefficients are higher in as-cast, unaged films than in as-cast films aged at ambient conditions a nd increase to a maximum in both unaged and aged as-cast films after methan ol conditioning. For example, the oxygen permeability of a 20-mu m-thick as -cast film is initially 100 barrer and decreases to 40 barrer after aging f or 1 week at ambient conditions. After methanol treatment, the oxygen perme abilities of unaged and aged films increase to 430 and 460 barrer, respecti vely. Thicker as-cast films have higher gas permeabilities than thinner as- cast films. Propane and n-butane sorption isotherms suggest significant cha nges in the nonequilibrium excess free volume in these glassy polymer films due to processing history. For example, the nonequilibrium excess free vol ume estimated from the sorption data is similar for as-cast, unaged samples and methanol-conditioned samples; it is 100% higher in methanol-conditione d films than in aged, as-cast films. The sensitivity of permeability to pro cessing history may be due in large measure to the influence of processing history on nonequilibrium excess free volume and free volume distribution. The propane and n-butane diffusion coefficients are also sensitive to film processing history, presumably because of the dependence of diffusivity on free volume and free volume distribution. (C) 2000 John Wiley & Sons, Inc.