No abstract

A solid-state sulfonation procedure on syndiotactic polystyrene (s-PS) δ-form films allows an easy and uniform sulfonation of the phenyl rings of the amorphous phase and preserves the nanoporous δ-phase. The high degree of sulfonation of the amorphous phase (up to a molar ratio 2/1 between phenyl rings and sulfonic groups) makes this phase highly hydrophilic, whereas the hydrophobic crystalline phase maintains its guest sorption ability. s-PS films, sulfonated only in the amorphous phase and exhibiting the nanoporous δ-phase, present kinetics of guest sorption from water solutions into the crystalline phase, being markedly higher than those of the corresponding unsulfonated films. For instance, DCE sorption kinetics from 50 ppm aqueous solutions show an unaltered DCE equilibrium uptake (close to 4 wt %) associated with a DCE diffusivity increase of more than 70 times. Moreover, the nanoporous crystalline phase and its sorption ability remain essentially unaffected by water sorption/desorption cycles. The reported results hence indicate that these new materials are particularly suitable for removal of VOC pollutants from water and moist air.

Monolithic syndiotactic polystyrene (s-PS) aerogels, formed by highly crystalline nanofibrils with a hydrophobic nanoporous-crystalline phase and a hydrophilic amorphous phase have been prepared and characterized. These aerogels, with a high degree of sulfonation of the amorphous phase and nearly negligible sulfonation of the crystalline phase, are obtained by treating physical gels exhibiting δ-clathrate form. With respect to unsulfonated nanoporous-crystalline polymeric aerogels, these new selectively sulfonated aerogels present the great advantage of a high water diffusivity and water uptake up to 600 wt %. This water uptake increases greatly the sorption kinetics of organic pollutants by the hydrophobic nanopores of the crystalline phase. For instance, for aerogels with a sulfonation of 10%, the diffusivity of a volatile organic compound (1,2-dichloroethane, DCE) from 10 ppm aqueous solution is more than 3 orders of magnitude higher than that for the unsulfonated aerogel and is very close to the DCE diffusivity in water.