Production of aromatic polyketones

Production of an aromatic polyketone by reacting in the presence of a quinquevalent phosphorous halide (preferably PCl5) and a fluoroalkane sulphonic acid (preferably CF3SO2OH) the reactants selected from: (a) a mixture of (i) at least one aromatic dicarboxylic acid HO2C-Ar-CO2H where -Ar'- is a divalent aromatic radical and CO2H is an aromatically bound carboxylic acid group, which dicarboxylic acid is polymerizable with the at least one aromatic compound of (ii), and (ii) at least one aromatic compound H-Ar'-H where -Ar'- is a divalent aromatic radical and H is an aromatically bound hydrogen atom, which compound is polymerizable with the at least one dicarboxylic acid of (i); (b) at least one aromatic monocarboxylic acid H-Ar''-CO2H where -Ar''- is a divalent aromatic radical and H and CO2H are as defined in (a), which monocarboxylic acid is self-polymerizable; and (c) a combination of (a) and (b).