The mechanism of light gas transport through configurational free volume in glassy polymers

A possible mechanism of small molecule transport in glassy polymer membranes containing configurational free volume (i.e., triptycene moieties) is proposed. To this aim, a family triptycene-containing polybenzoxazoles (TPBOs) exhibiting systematically varied molar amount units, ranging from 25% to 100%, was selected perform light gas (N 2 , CH 4 and CO ) fundamental sorption-transport study. The dual mode sorption-mobility model used isolate the effect on penetrant transport. Henry's Langmuir's diffusion coefficients were estimated quantify contributions /CH diffusivity-selectivity as function content TPBOs. Interestingly, while changes little with increasing volume, increases up infinity when concentration 75% or higher, showing that larger molecules increasingly hindered relative smaller (i.e. more incorporated polymer. In sharp contrast, pure- mixed-gas sorption, well solubility-selectivity, essentially unaffected by content. According physical picture, analysis isosteric heats sorption indicates TPBOs plasticization resistance independent • volume-containing polymers weakly depends volume. Configurational does not affect coefficient. competitive sorption.