The influence of structural parameters on the glass temperature and compatibility of poly(phenylene ether ketone)s

It is shown that the glass temperature of poly(phenylene ether ketone)s (PEKs) decreases with increasing number of intercalated phenylene thioether units in the main chain. The decrease is similar for the different classes of poly(phenylene ether ketone)s, i.e. poly(phenylene ether ether ketone)s, poly(phenylene thioether ether ketone)s, and poly(phenylene ether sulphone ketone)s. At the same time, the compatibility of such PEK families with poly(phenylene ether sulphone) decreases. The compatibility changes are explained by the disturbing effect of the intercalated phenylene thioether units on the matching of the rigid pairs of phenylene units stiffened by the intercalated sulphone or ketone units, respectively. Although the glass temperatures roughly obey the mass/'flexible' bond rule of Schneider-Di Marzio, for a more exact prediction additional volume effects of the flexible groups have to be considered.