Crystalline modifications, exhibiting largely different X-ray diffraction\ud patterns, have been obtained for poly(2,6-dimethyl-1,4-phenylene)oxide (PPO), by\ud gel desiccation procedures as well as by solvent-induced crystallization of amorphous\ud films. The choice of the solvent allows controlling the nature of the crystalline phase.\ud Both amorphous and semicrystalline samples of this commercial thermoplastic\ud polymer exhibit a high uptake of large guest molecules (like, e.g., benzene or carbon\ud tetrachloride), both from vapor phases and from diluted aqueous solutions. Surprisingly,\ud the semicrystalline PPO samples present guest solubility much higher than fully\ud amorphous PPO samples. These sorption experiments, as well as density measurements\ud and classical BrunauerEmmettTeller (BET) experiments, clearly indicate\ud that the obtained PPO crystalline phases are nanoporous. For these thermally stable\ud PPO-based materials exhibiting nanoporous crystalline and amorphous phases, many\ud applications are predictable

Monolithic aerogels can be easily obtained by drying physical gels formed by linear uncross-linked polymers. Preparation methods, structure, and properties of these physically cross-linked polymeric aerogels are reviewed, with particular emphasis to those whose cross-linking knots are crystallites and, more in particular, crystallites exhibiting nanoporous-crystalline forms. The latter aerogels present beside disordered amorphous micropores (typical of all aerogels) also all identical nanopores of the crystalline phases. Their outstanding guest transport properties combined with low material cost, robustness, durability, and ease of handling and recycle make these aerogels suitable for applications in chemical separations, purification, and storage as well as in biomedicine. Scientific, technological, and industrial perspectives for monolithic nanoporous-crystalline polymeric aerogels are also discussed.

BACKGROUND: Heterogeneous photocatalysis for the degradation of non-biodegradable organic contaminants in wastewater is an alternative to traditional treatment techniques. Since the applications developed employ photocatalysts in powder form, a main disadvantage remains related to the recovery of photocatalysts from the treated wastewater, resulting in damage and shorter lifetime for the recirculation pumps. Structured photocatalysts offer a valid solution to simplify the process; however, they have to guarantee light transmission, long-term stability under different operating conditions and under mechanical stress. RESULTS: The photocatalytic performances of N-doped TiO 2 nanocomposite syndiotactic polystyrene aerogels (Nt-sPS) were analyzed in the presence of visible light. A widely used model pollutant, methylene blue (MB), was chosen to verify the photocatalytic performance. After about 180 min of irradiation, on Nt-sPS, the conversion of MB reached 30%, higher than that obtained (16%) when the photocatalyst is suspended as powder in the liquid reaction medium. CONCLUSION: N-doped TiO 2 , obtained by direct nitration during the hydrolysis of titanium tetraisopropoxide with ammonia solutions, was immobilized in s-PS aerogels, yielding high activity in the removal of methylene blue under visible light irradiation, in comparison with N-doped TiO 2 dispersed as powder in solution.

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Guest-induced cocrystallization of amorphous poly(2,6-dimethyl-1,4-phenylene ether) (PPO) films has been investigated, mainly by X-ray diffraction and FTIR spectroscopy. Two different kinds of uniplanar orientations have been found for PPO cocrystalline phases with α-pinene, which present their (110) and (200) crystal planes preferentially parallel to the film plane (f 110 = 0.90 and f 200 = 0.75, respectively). Both kinds of uniplanar orientations can be fully retained after guest-exchange procedures leading to cocrystalline forms, which maintain unaltered the polymer host conformation, like those with decalin or tetralin. The formation of different kinds and high degrees of uniplanar orientations, as until now observed only for syndiotactic polystyrene cocrystallization, suggests that solvent-induced uniplanar orientations, for high film thickness and without any mechanical process, are generally associated with the formation of polymer cocrystalline phases.