Thermal, Electrical, and Gas Transport Properties of New Aromatic Poly(Ether Ether Ketone)/Silica Hybrid Films

Abstract

New hybrid films were prepared through a sol–gel process starting from a poly(ether ether ketone)‐containing pendant carboxyl groups (PEEK‐R) and various alkoxysilanes (tetraethoxysilane, methyltrietoxysilane, and phenyltriethoxysilane) as precursors of the inorganic network. PEEK‐R was synthesized from 4,4′‐difluorobenzophenone and a mixture of phenolphthalein and phenolphthalin. Owing to the presence of polar phthalide and carboxyl groups in the PEEK‐R structure, the hybrid films showed homogeneous morphologies. The films exhibited good thermal stability, having initial decomposition temperature over 440°C and a glass transition of 180–218°C. The contact angle values of film surfaces with water and ethylene glycol increased by the introduction of silica. The dielectric spectroscopy analysis at lower temperature evidenced two secondary relaxation processes, γ and β. At higher temperature, a conductivity relaxation was observed. The thermal activation energy of conductivity was in the range of 0.6–1.02 eV, confirming the electronic conduction via hopping. Gas permeation tests using small molecules (He, N2, O2, and CO2) indicated that hybrid films showed higher permeability than pure polymer film for all tested gases. The permeability increase was accompanied by a slight reduction in selectivity, but CO2/N2 selectivity remained significantly high making this type of hybrid materials promising candidate for gas separation membranes. POLYM. COMPOS., 39:E1544–E1553, 2018. © 2017 Society of Plastics Engineers