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 nanoporous-crystalline phases and their uniplanar orientations, is explored. The study is conducted on syndiotactic polystyrene films, presenting a nanoporous-crystalline phase (δ or ε) or the dense γ 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 δ form films with a//c// orientation and maximum for ε form films with c⊥ uniplanar orientation. These results can be easily rationalized on the basis of crystal structure considerations.