Synthesis, Characterization and Properties of SiO2-Polyimide Hybrid Film

Abstract

A polyamic acid (PAA) solution with a solids content of approximately 15 wt% was synthesized by reacting pyromellitic dianhydride with 4,4'–diaminodiphenyl methane in N-methyl-2-pyrrolidone through a ring-opening polyaddition. A nano-SiO2 precursor was also synthesized from tetraethoxysilane (TEOS) via a sol-gel process. SiO2-polyimide (SiO2-PI) hybrid films were then successfully prepared. The polyimide (PI) film and the SiO2-PI hybrid films were characterized by FT-IR, XPS and SEM. The FT-IR spectra showed that PAA became imidized completely after a heat treatment process. The analyses by FT-IR, XPS and SEM confirmed that most of the TEOS had changed into nanoscale SiO2 particles, distributed homogeneously in the PI matrix. Nano-indenter XP was employed to detect the nano-indentation harness and nano-indentation modulus of the films. The results indicated that the mechanical properties of the SiO2-PI hybrid films were better than those of PI film, and the SiO2 content of the SiO2-PI hybrid films had an obvious effect on their nano-indentation properties. When the SiO2 content was 5 wt%, the maximum values of the nano-indentation hardness and nano-indentation modulus were 0.870 GPa and 6.974 GPa, respectively. TGA evidence suggested that the thermal stability of the SiO2-PI hybrid film was better than that of PI film, and the thermal decomposition temperature was increased from 547.8 oC to 567.5 oC.