Process-morphology-property Relationships in Strut-like Poly(ether ether ketone) Aerogels Prepared through Thermally Induced Phase Separation

Abstract

Poly(ether ether ketone) (PEEK) aerogels resulting from gelation in 1,3-diphenyl acetone (DPA) were prepared for the first time. The phase separation mechanism was determined to be solid-liquid phase separation which resulted in the formation of aerogels consisting of crystalline axialites. These axialites formed a strut-like network that had superior compressive properties compared to the globular aerogels previous prepared from the gelation of PEEK in 4-chlorophenol and dichloroacetic acid. It was also found that strut-like PEEK or poly(phenylene sulfide) (PPS) aerogels prepared from gelation in DPA were mechanically robust such that they could resist the forces imposed on the gel during drying. Monolithic strut-like PEEK or PPS aerogels were prepared with vacuum-drying, freeze-drying, and supercritical CO2 extraction with minimal shrinkage and deformation. The weaker globular PEEK aerogel morphologies suffered from considerable shrinkage due to capillary forces or ice crystal growth induced on vacuum-drying or freeze-drying, respectively. Determining the gelation mechanism of PEEK in DPA allowed for effective manipulation of the processing parameters. It was found that changing the gelation temperature improved the mechanical properties of PEEK aerogels. Dissolution temperature can also be lowered to improve the nucleation density of PEEK aerogels.