Nanoporous-crystalline poly(2,6-dimethyl-1,4-phenylene)oxide (PPO) aerogels

Monolithic aerogels of poly(2,6-dimethyl-1,4-phenylene)oxide (an industrially relevant polymer generally known as polyphenyleneoxide or PPO), have been prepared and characterized. These aerogels obtained by supercritical carbon dioxide extraction of thermoreversible gels of high molecular weight PPO present an apparent porosity typically in the range 70%–95% and high surface area values up to 750 m2/g. Moreover these aerogels are characterized by an excellent sorption uptake of organic pollutants at low vapor pressure and good recyclability by thermal regeneration. Good mechanical properties and dimensional stability of PPO monoliths is due to the polymer high molecular weight which ensures formation of a fibrillar morphology, already in the precursor gel. Sorption capacity and recyclability of PPO aerogels are mostly due to their crystalline phase: (i) its nanoporous-crystalline structure assures high specific surface areas; (ii) its high melting temperature assures a high thermal monolith stability as well as easy and cheap recovery of absorbed guest molecules by thermal treatments rather than by solvent extractions.