Structural investigations of polymer liquid-crystalline solutions: Aromatic polyamides, hydroxy propyl cellulose, and poly(γ-benzyl-L-glutamate)

A comparative structural investigation of the characteristics of polymer liquid‐crystalline solutions including Kevlar® (PPD‐T)/sulfuric acid, poly(Cl‐ p ‐phenylene terephthalamide) (Cl‐PPD‐T)/sulfuric acid, poly(γ‐benzyl‐ L ‐glutamate) (PγBLG)/dioxane, and hydroxypropyl cellulose (HPC)/water was undertaken. Experimental procedures included polarized light microscopy, light scattering, absorption spectra, and x‐ray diffraction on solutions at various concentrations and temperatures. Both the two‐phase region at the onset of liquid‐crystal formation and the wholly anisotropic phase were investigated. Each solution exhibited distinctive characteristics. The PPD‐T and Cl‐PPD‐T solutions were nematic, and the PγBLG and HPC solutions were cholesteric. In the two‐phase region the PPD‐T, Cl‐PPD‐T, and PγBLG (but apparently not the HPC) exhibited negatively birefringent spherulites and aggregates of spherulites. The HPC solutions only exhibited spherulitic structures in the single‐phase anisotropic system. The structures and orientations in the anisotropic phase for the various polymer solutions is considered. The helicoidal structural characteristics of the PγBLG and HPC solutions are contrasted.