Ordered structure of polyallylamine hydrochloride in dilute solutions as studied by small angle X-ray scattering

Aqueous solutions of polyallylamine hydrochloride were examined by small angle x-ray scattering. When the polymer concentration of coexisting simple salt was low, a single, broad peak was observed. The peak was interpreted as indicating the presence of an ordered arrangement of macroions in the solutions. The intermacroion spacing was calculated by the Bragg equation and found to be much smaller than the average intermacroion spacing calculable from the polymer concentration, suggesting that there exist ordered regions and at the same time disordered regions in the solutions. The Bragg spacing decreased with increasing polymer concentration and increased with increasing salt concentration. Mixing of two samples of different molecular weights gave a new scattering peak in between the original peaks of the mother samples, which supports the intermolecular nature of the ordering. The peak height was lowered with increasing temperature. The scattering peak was found to stay unaffected for 21 days.