A range of particulate poly(ether ketone ketone)s (PEKKs) have been synthesised by a room temperature Friedel–Crafts dispersion polymerisation. Their properties, including glass transition, melting and crystallisation temperatures, the degree of crystallinity and particle size, were readily controlled by altering the ratio of 1,3- to 1,4-units in the polymer backbone. The bulk polymer properties are comparable to materials produced by alternative methods and the polymers are highly melt stable. Unusually, all PEKKs are highly crystalline as produced, although some become amorphous on further processing. Evidence was obtained which is consistent with the particulate product being formed by a seeding mechanism, from aluminium(III) seeding particles which are formed in situ.