Control of guest transport in polymer films by structure and orientation of nanoporous-crystalline phases

The possibility to control guest transport in polymer films, by selecting between available nanoporouscrystalline phases and their uniplanar orientations, is explored. The study is conducted on syndiotactic polystyrene films, presenting a nanoporous-crystalline phase (delta or epsilon) or the dense gamma phase and exhibiting uniaxial orientation or each of the three known uniplanar orientations. In particular, the different films are compared as for the uptake of a relevant pollutant (1,2-dichloroethane) from dilute aqueous solutions. High guest solubility is observed only for films exhibiting the nanoporous-crystalline phases while the diffusivity is minimum for delta form films with a(parallel to)c(parallel to) orientation and maximum for epsilon form films with c(perpendicular to) uniplanar orientation. These results can be easily rationalized on the basis of crystal structure considerations. (C) 2013 Elsevier Ltd. All rights reserved.