Semicrystalline syndiotactic polystyrene (s-PS) films, for all crystalline phases based on helical chains (δ, γ and clathrates), have been prepared with high degrees of three different kinds of uniplanar orientation. In particular, by suitable solution- or solvent-induced crystallizations, (010), (002), or (2̄10) crystalline planes of the nanoporous δ and clathrate phases can be oriented preferentially parallel to the film plane. To our knowledge, the achievement for a given polymeric crystalline phase of high degrees of three different uniplanar orientations is unprecedented. This is particularly relevant for s-PS due to the functional properties of its nanoporous crystalline δ phase as well as of its clathrate phases. As for the clathrate phases, it is also worth noting that, since each cavity of the clathrate phase generally includes one isolated guest molecule whose mobility is generally low, the control of the orientation of the host crystalline phase also allows the control of the orientation of the guest molecules.

Nanoporous crystalline structures can be achieved for a large variety of chemical compounds: inorganic (e.g., zeolites), 1 metal-organic, 2 as well as organic. 3 These materials, often referred as inorganic, metal-organic, and organic "frameworks", are relevant for molecular storage, recognition, and separation techniques.Recently, a "polymeric framework", i.e., a semicrystalline polymeric material presenting a nanoporous crystalline phase, has also been discovered. [4][5][6] In fact, the δ-phase of syndiotactic polystyrene (s-PS) presents two identical cavities and

Thermal transitions of the three crystalline phases (γ, δ, and ε) of syndiotactic polystyrene (s-PS), presenting s(2/1)2 helices, have been compared by X-ray diffraction, differential scanning calorimetry (DSC), and dynamic-mechanical analyses. These analyses have been conducted on crystalline (δ and ε) films, obtained by similar solvent sorption and desorption procedures, starting from a same γ-form film. The Fourier transform Infrared (FTIR) spectra of the three films have also been compared. The obtained results indicate that the recently discovered ε-phase, as the already known δ-phase, is transformed in γ-phase by heating above 100 °C. However, the ε → γ transition occurs directly without the formation, for intermediate temperatures, of a helical mesomorphic phase, as instead observed for the δ → γ transition. DSC studies and FTIR measurements also suggest that the crystalline packing of the ε-form could be rather similar to that one of the γ-form.