Membrane diffusion is an inherently slow process. Consequently, membrane-based separation processes can be only economically viable if extremely thin, defect-free membranes are used. Thin-film composite membranes with a permselective layer thickness down to about 0.5 m can be made by presently available techniques. The goal of this program is to develop the technology for making industrial-scale composite membranes with a permselective layer thickness of 0.1 m or below. The membranes will be made by solution coating an elastomeric polymer material onto a microporous support. The upper surface of the coated layer will then be converted to a glassy crosslinked zone by surface treatment with a reactive organic species. The result will be a zone of thickness less than 0.1 m with greatly enhanced selectivity. Because the glassy layer is so thin, the flux will also be very high compared with that of a standard composite membrane with a glassy permselective layer.
