Ab initio and molecular mechanics study of polyaryl ether ketone polymers

Abstract

Ab initio calculations on fragments of polyether ketone polymers are used to determine both inter- and intramolecular forces in these systems. The results indicate that, even for these conjugated systems, it is possible to choose relatively small fragments which are representative of the complete system. The information generated is used to calculate the crystal structure of several poly(aryl–ether–ketone)s, including poly(phenylene oxide), PEK, PEKK and PEEK. The calculated perfect structures are in good agreement with experimental information from X-ray crystallography. Experimental trends in the a-, b- and c- lattice parameters, observed as the ketone content of the polymer is altered, are also reproduced. Metastable crystal structures for several of the polymers are predicted, which are very close to a new crystal structure proposed recently for PEKK.