Light-scattering of polyamide hydrazide solutions and conformational characteristics of its molecules

Light-scattering measurements have been carried out for 18 samples of polyamide hydrazide (PAH) in dimethylsulphoxide (DMS) with an over 10-fold variation in molecular weights. It was shown that the excluded volume effect in DMS does not appreciably affect the size of PAH molecules. The length of the Kuhn segment (A ≈ 240 · 10^?8 cm) was estimated from the experimental determinations of molecular weights $\text{M}{}_{\mathrm{w}}$ and the radii of gyration 〈R²〉_z. Viscometric determination of the rigidity of PAH chains yields the value of A ≈ 200 · 10^?8 cm and the hydrodynamic diameter d ≈ 5 · 10^?8 cm. The whole collection of data shows that PAH is a typical rigid-chain polymer; the extended conformation is due to the backbone rigidity tather than to the excluded volume effects.