Functional Chromium Wheel-Based Hybrid Organic-Inorganic Materials for Dielectric Applications

The first example of organic-inorganic hybrid materials based on the embedding of a chromium-nickel wheel cluster {[(n-C3H7)(2)NH2]-[Cr7NiF8(O2C4H5)16]} (Cr7Ni) MW poly(methyl methacrylate) (PMMA) and the characterization of the dielectric properties of the obtained material is described By an optimized copolymerization of the methacrylate-functionalized chromium-nickel wheel with ethyl methacrylate in a cluster/monomer 1:200 molar mixture, a homogeneious hybrid material CrNi_MMA200 is obtained. The electrical responses of the non-doped PMMA and of the hybrid material were studied by broadband dielectric spectroscopy (BDS) from 0.01 Hz to 10 MHz and over the temperature range of 5-115 degrees C. The permittivity profiles reveal two relaxation peaks in the materials, which correspond to the alpha and beta relaxation modes of the PMMA matrix. The-position of these modes shifts toward higher frequencies as. temperature increases. BDS is a powerful tool revealing the intimate miscibillity of the various components of the hybrid material, thus indicating that, on a molecular scale, the material proposed is a homogeneous system. Finally, a value of the dielectric. constant of 19 at 25 degrees C and 1 kHz is determined. This value is noticeably lower than the value of 3.2 obtained for pristine PMMA prepared following the same synthesis protocol. Thus, these results classify the hybrid CrNi_MMA200 as an appealing starting material for the development of dielectric polymeric layers for the development of innovative capacitors, transistors, and other microelectronic devices. The vibrational properties of the hybrid materials are investigated by Fourier-transform infrared (FT-IR) and Raman spetroscopy, whereas the thermal behavior is analyzed by thermogravimetric analysis (TGA). Swelling experiments are used to qualitatively evaluate the crosslinking density of the hybrid materials. The integrity of the wheels once embeeded in the macromolecular backbone is confirmed by extended X-ray absorption fine structure (EXAFS) and electron spin resonance (E-PR) spectroscopic measurements.