Thermal Stability of Nanoporous Crystalline and Amorphous Phases of Poly(2,6-dimethyl-1,4-phenylene) Oxide

A study of the thermal stability of the outstanding sorption properties of nanoporous-crystalline and amorphous phases of poly(2,6-dimethyl-1,4-phenylene) oxide (PPO) is presented. In particular, the structural changes, as induced by thermal treatments in the temperature range 100−270 °C, of two limit nanoporous-crystalline modifications have been investigated by wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). Although both PPO nanoporous-crystalline modifications are metastable, their crystallinity reduction is small for thermal treatments up to 200 °C. For the entire thermal treatment range, the uptake of benzene from vapor phase for the PPO nanoporous-crystalline samples is higher than for PPO nanoporous-amorphous samples. After thermal treatments above the polymer glass transition temperature (Tg ≈ 220 °C), the guest solubility becomes negligible for the fully amorphous samples, while remains large for the nanoporous-crystalline phases, up to the polymer melting (Tg ≈ 250 °C). This high thermal stability of sorbent materials based on PPO nanoporous-crystalline phases is particularly relevant for their thermal regeneration processes