Electrostatic cross-linking-induced self-assembly of poly(allylamine hydrochloride) using Allura Red AC

The self-assembly of poly(allylamine hydrochloride) (PAH) through electrostatic cross-linking using Allura Red AC (AR) was explored in an aqueous solution. PAH showed no self-assembly in the absence of AR. A light-scattering study demonstrated that PAH formed aggregates of ca. 300-nm diameter by the addition of AR at 0.1 of the molar ratio of the SO₃Na unit of AR to NH₃Cl of PAH (SO₃Na/NH₃Cl). The PAH diameter decreased as the SO₃Na/NH₃Cl ratio increased up to 0.5 and thereafter rapidly increased due to sedimentation of the aggregates. The analysis of the normalized time correlation function of the scattered field confirmed that the electrostatic cross-linking by AR provided polydispersed aggregates of PAH. The UV analysis revealed that the PAH self-assembly caused a blue shift of AR. The size of the aggregates was independent of the PAH concentration. On the other hand, the aggregate size was strongly dependent on the temperature.