Critical Role of Diffraction Simulation in Establishing the Crystal and Molecular Structures of Poly(biaryl ether ketone)s

Abstract

Molecular modeling and diffraction simulation studies of the biphenyl-based poly(ether ketone)s [O-Ar-Ar-O-Ar-CO-Ar-Ar-CO-Ar-]n ( 3) and [-O-Ar-Ar-CO-Ar-]n (4, Ar ) 1,4phenylene), coupled with data obtained from an oligomer single-crystal study, have enabled their crystal and molecular structures to be determined from X-ray powder data. A crystallographically disordered structure in which the ether and ketone linkages are distributed randomly over the bridging positions of the polymer chain is potentially available to both polymers and undoubtedly occurs in their random 1:2 copolymer (5). The disordered structure is monoclinic (rather than orthorhombic as has previously been proposed), in space group P2 1/b, with two chains per unit cell. Rietveld refinement of this structure for polymers 3 and 4, based on X-ray powder data, gave final agreement factors (Rwp) of 5.7% and 6.6%, respectively. Analysis of X-ray fiber data by diffraction simulation methods suggests that the disordered structure always predominates for 3 but that a partially ordered arrangement of ether and ketone linkages is present in oriented samples of polymer 4.

A Class of Rigid–Flexible Coupling Crystalline Crosslinked Polymers as Vapomechanical Actuators

“…Flexible PEG spacers act as edges to link the rigid chain polymer arrays formed by the condensation of hydrazine and aldehyde. Unlike traditional chain polymers that are densely packed through a variety of intermolecular interactions, [31] such as hydrogen bonding, CCP 400 ‐1 is dominated by the interlayer π–π stacking interactions between the formed rigid polymer chains (Figure 2c). And these rigid polymer chains orderly stacked onto each other yield a broad stacking peak.…”