Reduction of mesoporous poly(ether ether ketone) materials, preserving pore size

Poly(ether ether ketone) (PEEK) is an important high-performance engineering polymer that is used extensively in numerous engineering applications that require chemical, solvent and thermal resistance. These attributes make PEEK attractive for the preparation of porous materials and membranes. Chemical modifications of preformed porous PEEK materials can expand the utilization of PEEK in a range of applications. It is desirable to carry out chemical functionalization without affecting the preformed porous structure or the degree of polymer crystallinity responsible for the sought-after properties. We report here on the heterogeneous functionalization of preformed mesoporous PEEK materials with hydroxyl groups using sodium borohydride as a reducing agent in a poly(ethylene glycol)/tetrahydrofuran solvent mixture. The pore structure of functionalized materials was characterized, and the degree of modification with functional groups was measured as a function of reaction protocol. The methodology was applied to the preparation of porous PEEK materials in the form of beads and hollow fibers that differed in semicrystalline morphology and pore structure. The degree of surface modification by –OH groups in reduced PEEK (PEEK-OH) porous materials was determined quantitatively by measuring the carbocation adduct concentration formed upon the dissolution of PEEK-OH in sulfuric acid using UV–visible spectroscopy. Bis(4-(4-methoxyphenoxy)phenyl)methanone was used to optimize the reaction condition protocol. The degree of crystallinity and pore structure of the functionalized articles were largely preserved following modification.