212 HIGH PERFORMANCE POLYMERS
8.2 Polymerization and Fabrication
Similarly to poly(ether ketone)s (PEK)s, PENs have
been prepared according to a nucleophilic route and an
electrophilic route.
8.2.1 Electrophilic Route
PEKs that are subsequently end capped with nitrile
functions have been prepared by Friedel-Crafts poly-
merization [26]. For example, m-hexaphenyl ether is
reacted with p-cyanobenzoyl chloride with AlCl
3
as
catalyst in dry 1,2-dichloroethane to form a nitrile end-
capped oligomer [27]. In another study, 5-cyanoisoph-
thaloyl chloride was used as a nitrile-containing
comonomer for the Friedel-Crafts polymerization [28].
In the Friedel-Crafts polymerization, the nitrile com-
pound need not necessarily bear a chlorine function, if
another aromatic ...