Structural studies of crystalline poly(p‐phenylene oxides) II. Poly(2.6‐diphenyl p‐phenylene oxides)

Abstract

AbstractPoly(2,6‐diphenyl p‐phenylene oxide) exists in at least two crystalline modifications. One modification can be obtained by crystallization from solution or by thermal crystallization of undiluted polymer. The other modification, however, can only be obtained by crystallization from solution. The solvent, e. g. chloroform, is assumed to form an indispensable part of the crystal lattice of the latter modification. magnified imageBy X‐ray diffraction methods the structure of the former modification has been investigated. The unit cell is tetragonal and has the following dimensions: a = b = 12.51 Å, and c (fiber axis) = 17.08 Å. Two enantiomorphous space groups (P41212‐D and P43212‐D), are possible; we have arbitrarily chosen space group P41212‐D. The unit cell contains eight monomeric units. Four monomeric units are contained in the fiber identity period. The two molecular chains that pass through the unit cell assume a helical conformation (41‐helix) and run in opposite directions with respect to their phenyl side groups. The oxygen bond angle is about 127°.The atomic positions in the unit cell have been determined by comparing the intensities calculated with the intensities observed. The planes of the phenylene groups in the molecular backbone are nearly parallel to the c‐axis. The planes of the phenyl side groups are nearly perpendicular to the plane of the phenylene group to which the side groups are attached.