Hydrogel with cubic-packed giant concentric domains of semi-rigid polyion complex

Abstract

We report a novel giant oriented structure observed in plate hydrogels synthesized by photo-polymerization of cationic monomers with a cross-linker in the presence of a semi-rigid polyanion as the dopant. The giant structure, formed viaself-assembly of the semi-rigid polyion complex, consists of millimetre-scale cubic packed concentric cylindrical domains that are sandwiched by two homeotropically aligned outer layers. A universal relationship between the diameter of the cylinders D and the thickness of the swollen gel T is observed, as D = 0.5T, regardless the change in the concentrations of the polyanion and precursor cationic monomer. This result permits us to induce the giant concentric structure into hydrogels with tunable cylindrical sizes.