Calculation of barriers to rotation in PEEK and some of its substituted derivatives

Abstract

Barriers to rotation have been calculated by molecular mechanics, using the force field MM+, for a fragment of PEEK and its methyl, ethyl, isopropyl, tert-butyl and di-tert-butyl, substituted derivatives. The barrier for the nearer C—O bond increases from 2.0 kcal/mol in KEEK to 16 kcal/mol in dibutyl substituted KEEK as the bulkiness of the substituent increases. The rotation barrier of the further C—O bond is not affected by the substituent. Keywords: rotation barriers, PEEK, molecular mechanics.