Conformational Characteristics and Flexibility of Poly(2,6-disubstituted-1,4-phenylene oxides) and the Polycarbonate of Diphenylol-2,2′-propane

Abstract

The conformational energies per independent repeat unit of poly(2,6-dimethyl-1,4-phenylene oxide) and the polycarbonate of diphenylol-2,2′-propane are evaluated through use of a 6-12 potential to account for the van der Waals interactions between nonbonded atoms and groups which accompany rotations about the backbone bonds. Energetically allowed conformations are found to span the entire range of the rotation angle about the virtual bonds connecting neighboring ether oxygen atoms in the phenylene oxide polymer. Rotation about the virtual bonds in the polycarbonate chain is found to be similarly free of significant contraints. Consequently, both classes of polymers exhibit freely rotating chain statistics, as previously deduced by others from experimental chain dimension measurements and chain symmetry arguments. However, rotation about the virtual bonds in the phenyiene oxide polymers and in polycarbonate is nearly truly free (each rotational state is appreciably populated) and not just restricted to two symmetrically located rotational states of equal energy at 90 and 270° as has been suggested. The flexibility of both classes of polymers, as manifested in their impact strength and fusion behavior, is discussed in light of the detailed conformational models (nearly true free rotation) developed here. The polysulfone chain is treated by analogy and is found to have a flexibility comparable to the poly(phenylene oxides) and polycarbonate. © 1972, American Chemical Society. All rights reserved.