Production of polyimide ceria nanocomposites by development of molecular hook technology in nano-sonochemistry.

Poly(amic acid), the precursor of polyimide (PI), was used for the preparation of PI/CeO2 nanocomposites (NC)s by ultrasonic assisted technique via insertion of the surface modified CeO2 nanoparticles (NP)s into PI matrix. In the preparation stages, in the first, the modifications of CeO2 NPs by using hexadecyltrimethoxysilane (HDTMS) as a binder were targeted using ultrasonic waves. In the second step, newly designed PI structure was formed from the sonochemical imidization process as a molecular hook. In this step two different reactions were occurred. The acetic acid elimination reaction in the main chain of macromolecule, and the acetylation reaction in the side chains of poly(amic acid) were accomplished. By acetylation process the hook structure was created for trapping of the modified nanoparticles. In the final step the preparation of PI NCs were achieved by sonochemical process. The structural and thermal properties of pure PI and PI/CeO2 NCs were studied by several techniques such as fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and thermal analyses. FT-IR and 1 H NMR spectra confirmed the success in preparation of PI matrix. The FE-SEM, TEM, and AFM analyses showed the uniform distribution of CeO2 NPs in PI matrix. The XRD patterns of NCs show the presence of crystalline CeO2 NPs in amorphous PI matrix. The thermal analysis results reveal that, with increases in the content of CeO2 NPs in PI matrix, the thermally stability factors of samples were improved.