Layer-by-Layer Polymeric Supramolecular Structures Containing Nickel Hydroxide Nanoparticles and Microcrystallites

Supramolecular polymer structures were assembled using the layer-by-layer, polyionic deposition technique. Depositing alternating layers of a polycation, poly(diallyldimethylammonium chloride), and a polyanion, poly(styrenesulfonate), formed the thin films. The nucleation of nickel hydroxide nanoparticles was achieved using a cyclical absorption−oxidation process in which nickel ions were absorbed into the polymer matrix (which bind to the sulfonate groups) and then oxidized in an alkali solution. Ultraviolet−visible spectroscopy was used to monitor the deposition of the thin film, as well as the subsequent nucleation and growth of nanoparticles within the supramolecular structure. Characterization of the nanoparticles using Fourier transform infrared spectroscopy showed the presence of the α form of nickel hydroxide, and X-ray diffraction analysis showed a mixture of both α and β forms of nickel hydroxide. Transmission electron microscopy images revealed fibrous, needlelike microcrystalline structures, increasing in size with absorption−oxidation cycles, surrounded by nanoparticles of approximately 5−50 nm in size.