Ordering in poly(allylamine hydrochloride) gels

Poly(allylamine hydrochloride) gels were prepared using N,N'-methylenebis(acrylamide) or glutaraldehyde as cross-linking agents. The gels were found to collapse when equilibrated with sodium salts of various organic acids. A less precipitous volume change was observed when equilibrated with NaCl and NaI. A small-angle X-ray scattering (SAXS) study was performed on the gels. A single broad peak was observed for the collapsed gels with the sodium salts of organic acids such as p-styrenesulfonate whereas no peak was found for the inorganic salts. The strong maximum in the SAXS patterns was attributed to the presence of ordered structures in the collapsed gels. The peak position shifted toward lower angles as the size of counterion was increased. A change in the peak position, though small, was noticed with variation in the charge density of the polymer, except for the less charged gel prepared at pH 10.5 which did not even collapse.