Mechanically robust and superhydrophobic aerogels of poly(ether ether ketone)

Abstract

The phase diagram for the thermoreversible gelation of poly(ether ether ketone) (PEEK) in dichloroacetic acid (DCA) was constructed over broad temperature and concentration ranges, revealing that PEEK is capable of dissolving and forming gels in DCA up to a weight fraction of 25 wt%. For PEEK solutions within this concentration range, the time required for gelation decreased with increasing temperature up to 80 °C, above which the gelation time increased considerably. Highly porous aerogels of PEEK were prepared through simple solvent exchange and lyophilization of the PEEK/DCA gels. Aerogel density was controlled by varying the PEEK concentration in solution, and shown to be unaffected by PEEK molecular weight (MW). Annealing PEEK aerogels prepared from relatively low concentration gels resulted in aerogels of increased density. Mechanical properties (in compression) were shown to improve with increasing density, resulting in equivalent compressive moduli at comparable density regardless of preparation method (concentration variation or annealing parameters). Additionally, density-matched aerogels from various MW PEEK showed a correlation between increasing MW and increasing compressive modulus. Contact angle and contact angle hysteresis revealed that PEEK aerogels have a high contact angle, suggesting superhydrophobicity, that decreases with increasing density and a very low contact angle hysteresis that increases with increasing density.