An inexpensive and reusable thermoplastic material that is promising in the field of chemical separations, and in particular of water and air purification from volatile organic compounds, is presented. This semicrystalline material based on syndiotactic polystyrene comprises a nanoporous crystalline phase where guest molecules can be clathrated. Changes of conformational equilibria of some chlorinated hydrocarbons upon clathration have been rationalized by a molecular mechanics approach. This sheds light on the nature of the host-guest interactions: although the van der Waals interactions are most relevant, the observed conformations for chlorinated guest molecules are essentially associated with electrostatic attractive interactions of quadrupolar conformers with a substantially quadrupolar electrostatic field of the crystalline cavity.