Tailored sequencing of highly brominated Poly(ether ether ketone) as a means to preserve crystallizability and enhance Tg

In this report, the bromination of poly(ether ether ketone) (PEEK) using the mild reagent N-bromosuccinimide (NBS) is explored to generate controlled random and blocky microstructures. Bromination proceeded quantitatively in both the solution state and semicrystalline gel-state, and degrees of bromination between 25 and 175 mol% were obtained for both random and blocky BrPEEK. Spectroscopic evidence revealed a higher prevalence of unfunctionalized repeat units for blocky BrPEEK than random BrPEEK at similar degrees of functionality. Furthermore, at similar degrees of bromination, blocky BrPEEK exhibited enhanced glass transition temperatures, greater crystallizability, higher melting temperatures, and faster crystallization kinetics than random BrPEEK, suggesting longer segments of unfunctionalized PEEK in blocky BrPEEK. Overall, this work demonstrates that PEEK can be brominated to very high degrees of substitution in the semicrystalline gel-state while preserving crystallizability and effectively blocking up the functionality. [Display omitted] •Quantitative bromination of PEEK was achieved.•Gel-state chemistry provided blocky microstructural control.•Microstructural control provided tunability of thermal properties.•Blocky microstructures enhanced material properties more than random.•Comparisons to Flory's theory of melting point depression in copolymers performed.