Polymers of a new class of glassy materials that demonstrate unusual solubility controlled permeability-metathesis Si-O-Si containing polynorbornenes-are synthesized. The introduction of bulky Si(OSiMe3)(3) substituents into the polynorbornene backbone is shown to provide the polymers with increased gas permeability, higher than all other known metathesis polynorbornenes. The prepared glassy polymers reveal behavior similar to that known for rubbers and, in particular, siloxanes: permeability coefficients increase for the penetrants of larger size. That is, these polymers are capable to remove higher hydrocarbons from natural and associated petroleum gases.