Conformational analyses of poly-ether-ether-ketone (PEEK), poly-ether-
nitrile (PEN) and their related polymers were performed using a semi-e
mpirical molecular orbital method with the Austin Model 1 Hamiltonian
(AM1 method in MOPAC). The minimum energy conformations were in good a
greement with those in crystal. structures of PEEK and PEN. The calcul
ated characteristic ratios C-infinity of the unperturbed end-to-end di
stance according to the rotational isomeric state theory were 3.93 for
PEEK and 6.73 for PEN. Numbers of repeating units between adjacent en
tanglements were also estimated.