Fabrication of Magnetic Thin Films by a Layer-by-Layer Self-Assembly Approach

The novel copolymer poly(5-methacryloylamido-1,10-phenanthroline-co-metliacrylic acid) (PMPMA) containing a phenanthroline ring was prepared by free radical polymerization. The synthesized monomer and copolymer have been confirmed by FT-IR, H-1 NMR spectra, and element analysis. A series Of multilayer films, which were fabricated via layer-by-layer self-assembly with the polymer PMPMA and the transition metal neutralized poly(styrene 4-sulfonate) (PSSNi or PSSCu) on thin plastic substrate polyethylene film (PE), were described. The coordination interaction between the two nitrogen atoms of the PMPMA and the transition metal ions of the PSSM was the driving force for building up the multilayer film, which was identified by infrared spectroscopy. UV-vis spectra and AFM images were applied to monitor these films, and the results indicate that the assembling process is relatively uniform. The magnetic behavior was examined as a function of magnetic field strength at 5 K and as a function of temperature (5-300 K). It is found that the films exhibit different magnetic properties from diamagnetic to magnetic transition to strongly ferromagnetic with the increasing cycles of film deposition. The magnetic results show that the different number of assembling layers can infect the alignment of adjacent paramagnetic spins from short linear to tridimensional fashion and induce different magnetic phenomena. The present study will provide a new mechanism to prepare organic materials with different demands for magnetic property.