Gas permeability and n-butane solubility of poly(1-trimethylgermyl-1-propyne)

Abstract

The gas permeability and n-butane solubility in glassy poly(1-trimethyl-germyl-1-propyne) (PTMGP) are reported. As synthesized, the PTMGP product contains two fractions: (1) one that is insoluble in toluene and soluble only in carbon disulfide (the toluene-insoluble polymer) and (2) one that is soluble in both toluene and carbon disulfide (the toluene-soluble polymer). In as-cast films, the gas permeability and n-butane solubility are higher in films prepared from the toluene-soluble polymer (particularly in those films cast from toluene) than in films prepared from the toluene-insoluble polymer and increase to a maximum in both fractions after methanol conditioning. For example, in as-cast films prepared from carbon disulfide, the oxygen permeability at 35 degreesC is 330 x 10(-10) cm(3) (STP) cm/(cm(2) s cmHg) for the toluene-soluble polymer and 73 x 10(-10) cm(3) (STP) cm/(cm(2) s cmHg) for the toluene-insoluble polymer. After these films are conditioned in methanol, the oxygen permeability increases to 5200 x 10(-10) cm(3) (STP) cm/(cm(2) s cmHg) for the toluene-soluble polymer and 6200 x 10(-10) cm(3) (STP) cm/(cm(2) s cmHg) for the toluene-insoluble polymer. The rankings of the fractional free volume and nonequilibrium excess free volume in the various PTMGP films are consistent with the measured gas permeability and n-butane solubility values. Methanol conditioning increases gas permeability and n-butane solubility of as-cast PTMGP films, regardless of the polymer fraction type and casting solvent used, and minimizes the permeability and solubility differences between the various films (i.e., the permeability and solubility values of all conditioned PTMGP films are similar). (C) 2002 Wiley Periodicals, Inc