Separation of gases using solubility-selective polymers

Polymeric membranes for the separation ofsupercritical gases are typically glassy and achieve high selectivity by a size-sieving mechanism. This property permits some polymers to be more than 100 times more permeable to hydrogen (kinetic diameter = 2.89A) than to methane (kinetic diameter = 3.8A), despite the fact that hydrogen solubility is markedly lower than methane solubility. The permeation properties of glassy polymers for the separation...