Polyaryletherketone (PAEK) thermoplastic composites via in-situ ring opening polymerisation

This work investigates the synthesis and characterisation of macrocyclic oligomers (MCO) from 4, 4′-difluoro benzophenone and catechol, their ring opening polymerisation, fabrication into carbon fibre reinforced composite materials and depolymerisation. The MCOs are polymerized using Caesium fluoride at a variety of temperatures, times, and catalyst concentrations to produce ortho polyaryletherketone polymers (oPAEK) of varying glass transition temperature (T_g) and molecular weight. A dimer formed during synthesis which does not polymerise is removed enabling a more convenient synthesis using lower temperature and catalyst concentration. The first carbon fibre composite of oPAEK fabricated using in-situ ring opening polymerisation methods is therefore presented with and without MCO dimer. Composites made without dimer formed are able fabricated at 10 °C lower temperature than the corresponding MCO containing dimer and have improved thermal and mechanical properties. Depolymerisation of the MCO and the re-emergence of cyclic structures is reported, highlighting the reversible nature of the chemistry. The results presented here provide important guidance on the future development of in-situ polymerisation of high performance thermoplastic composites.