Optical and dielectric studies of PMMA: precursors of BNT hybrid films

In this study, polymethyl methacrylate (PMMA)-based organic–inorganic hybrid films were deposited by the sol–gel technique by mixing the methyl methacrylate (MMA) organic precursor solution with an inorganic precursor solution of bismuth sodium titanate (Bi0.5Na0.5TiO3 or commonly known as BNT). 3-(trimethoxysilyl) propyl methacrylate (TMSPM) was used as coupling agent to improve the compatibility between the phases. The chemical composition and thermal stability were monitored by FTIR spectroscopy and thermogravimetric analysis. The high thermal stability observed together with the appearance of functional groups related to Si–O–metal interactions confirms the formation of a hybrid organic–inorganic material. A study of the optical properties by UV–Vis was also performed, where the refractive index between 2.1 and 2.6 was obtained, corroborating a good coupling between the organic and inorganic phases in the hybrid films. Atomic force microscopy measurements were also made to determine the surface morphology and roughness of the hybrid films and bear out their homogeneity. Finally, electrical measurements were performed by capacitance–voltage (C–V) and current–voltage (I–V), to obtain the dielectric permittivity constant with values from 15.5 to 18.5 and density current from 1 × 10−5 to 1 × 10−6 A cm−2. In comparison with other PMMA-based hybrid materials such as those containing the precursors TiO2 or SiO2, the PMMA–BNT hybrid material shows an improvement in its optical and dielectric properties.