Mechanism and kinetics of poly(ether ether ketone) (PEEK) sulfonation in concentrated sulfuric acid at room temperature. Part 2. Quantitative interpretation of model compound sulfonation

The mechanism and kinetics of sulfonation of two PEEK model compounds in co ncentrated sulfuric acid were studied. The first model compound (monomer) i s representative of a PEEK repeat unit. The second one is a PEEK dimer. Bec ause both model compounds are fluoroarylketone-ended, the sulfonation react ions were followed by F-19 NMR. The sulfonation reactions were treated following a first-order kinetics wit h respect to the unsulfonated PEEK repeat unit. The comparison between the monomer and dimer results showed two different types of sulfonation behavio ur. If only one apparent kinetic constant is considered for monomer sulfona tion, two kinetic constants were taken into account to describe the dimer s ulfonation process. This is due to a rate slowing effect of a sulfonic acid group on the sulfonation of the adjacent PEEK repeat unit. Furthermore, th e results also confirm the rate slowing effect of the fluorine atom on the sulfonation of the neighbouring PEEK repeat unit. (C) 2001 Society of Chemi cal Industry.