High Surface Area Nanoporous-Crystalline Polymer Films

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Based on a commercially available thermoplastic polymer (poly(2,6-dimethyl-1,4-phenylene) oxide, PPO), nanoporous-crystalline (NC) polymer films with a surface area (SA) higher than 600 m2 g–1 and with exceptionally fast organic pollutant uptakes are presented. Preparation procedures require fast crystallizations of amorphous films, as induced by high uptakes of nonvolatile guest molecules (typically in the range 70–90 wt %), followed by guest exchange with a volatile guest. The high SA of these NC PPO films is associated with a nanofibrillar morphology, analogous to those observed in physically cross-linked PPO aerogels. Organic pollutant diffusivities for high-SA NC PPO films are much higher than for other high-diffusivity PPO films, like for example those exhibiting NC phases with chain axes (and hence crystalline channels) being preferentially perpendicular to the film plane. Much higher diffusivities are observed both for guest sorption from vapor phase and from diluted PPO aqueous solutions and for guest desorption. Surprisingly, kinetics of guest uptakes from high-SA NC PPO films are even faster than for NC PPO aerogels and then much faster when referred to volume of the sorbent material. Because of their extremely fast kinetics of pollutant uptakes, associated with high thermal and mechanical stability, these new high-SA NC PPO films are expected to find many applications, mainly in pollutant remediation and molecular sensors.