Preparation, morphological and thermal stability of polyimide/silica hybrid material containing dye NBDPA

In this study, two series of the polyamide/silica NLO hybrid composites with covalent links between the inorganic and the organic networks were synthesized by the sol–gel method. These polyimide hybrid waveguide materials were prepared using a commercially available, 4,4′-(hexafluoro-isopropylidene)diphthalic arhydride (6FDA) or pyromellitic dianhydride (PMDA) as dianhydride, N-methyl-N-[4-[(6-nitrobenzothiazol-2-yl)diazenyl]phenyl]-2-aminoethano (NBDPA) as NLO-chain dye chromophore, 3-aminopropyltriethoxysilane (APTES) as a coupling agent between the organic and inorganic phase, and a metal alkoxide tetraethylorthosilicate (TEOS). The TEOS content in the hybrid films was varied from 0 to 22.5 wt%. The prepared polyimide/silica hybrids were characterized by IR, thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), etc. They exhibited fairly good optical transparency. The SiO2 phase was well dispersed in the polymer matrix. DSC and TGA results showed that these hybrid materials had excellent thermal stability. The refractive index decreased linearly with the increasing TEOS fraction in the hybrid films. The experimental results suggested that the hybrid thin films had potential applications as passive films for optical devices.