The conformation and the rigidity equilibrium of polyphenylquinoxalines

The hydrodynamic properties (sedimentation, diffusion, viscosity) and the flow birefringences have been studied on 3 polyphenylquinoxaline (PPQ) solutions having differing numbers of rotation bonds in the repetitive chain unit. The rigidity equilibrium parameters (length of the Kuhn segment) of the polymer molecules have been determined. A conformation analysis has been made of the PPQ chains which considered the likely stereo-isomers of the quinoxaline groups present in the molecules. The obstacles σ2 to intramolecular rotation have been determined and found to be close to those for aromatic polyamides. The experimental flow birefringence data indicated the molecules not to be storeo-regular. This explains the crystallization difficulties of the PPQ despite the considerable rigidity equilibrium of the molecular chains.