Preparation of Poly(amide-imide)-silica Hybrid Materials by Sol-gel Process

Abstract

Poly(amide-imide)-silica hybrid films were prepared using the sol-gel process of tetraethoxysilane (TEOS). A dianhydride-terminated poly(amide-imide) oligomer was prepared by the reaction of 4,4`-diphenylmethanediisocyanate (MDI) and trimellitic andydride (TMA) (MDI:TMA = 2:3 equivalents) in N-methylpyrrolidone (NMP) at 120 °C. One equivalent of 4,4′-diaminodiphenylmethane (DADPM) was added to the oligomer solution at room temperature to form the poly(amide-imide) precursor having carboxylic acid groups.The hydrolysis-polycondensation of TEOS could be carried out in the solution, and the poly(amide-imide)-silica hybrid film was obtained by casting the homogeneous silica-containing solution onto a glass plate, followed by heating at 300 °C. The silica content was 33 wt%, and silica particles with diameter of about 2 μm were observed in the hybrid films by scanning electron microscopy (SEM). Keywords:sol-gel process, poly(amide-imide)-silica hybrid, 4,4`-diphenylmethanediisocyanate, trimellitic andydride, 4,4′-diaminodiphenylmethane, tetraethoxysilane IntroductionThe sol-gel process is a method for preparation of inorganic metal oxides starting from organic metal alkoxides.The reaction consists of hydrolysis of the metal alkoxides, followed by polycondensation of the hydrolyzed intermediates. The sol-gel process has been applied in a polymer matrix to prepare inorganic and organic hybrid materials [1]. Polyimide-silica hybrid films have been successfully prepared by the sol-gel reaction of TEOS in polyamic acid solution, with subsequent heating of the resulting film at 270 °C. The hybrid film exhibited a higher modulus, lower coefficient of thermal expansion, and higher10 wt% loss temperature than non-hybrid films [2].We produced enameled wire having a polyimide-silica hybrid insulation layer prepared by the sol-gel process of TEOS [3,4]. TEOS was hydrolyzed and then polycondensed in a Kapton-type polyamic acid varnish, which is NMP solution, and the conductor was coated with the

Research Progress in High-Temperature-Resistant Electromagnetic Wire

“…After aging at 400 • C for 16 h, the hydrogen bonds formed by SiO 2 nanoparticles and carbonyl groups in PI inhibited the thermal degradation process of the hybrid films to a certain extent, and reduced the size and number of voids formed by thermal degradation [23].Using trimellitic anhydride (TMA), 4,4'-diaminodiphenylmethane diisocyanate (MDI), 4,4'-diaminodiphenylmethane (DADPM), and TEOS, Morikawa et al synthesized PAI/SiO 2 hybrid films containing 33% SiO 2 . The glass-transition temperature of the films was increased to 270 • C [24]. However, the doping of SiO 2 would lead to a decrease in the mechanical properties of the paint film and affect the application of the material.…”

Preparation of Polyimide-TiO₂ Hybrid Films by Synthesis of Polyamic Acid Having Carboxylic Acid Group Sidechains in the Presence of TiO₂

“…Because of these excellent characteristics, polyimides have been used in the aerospace industry and for electric and heat resistance applications [3][4][5][6][7].…”

Thermal Conversion of Polyamic Acid Gel to Polyimide Solution Having Amino Group Sidechains

“…Polyimide-silica hybrid materials have been prepared by a sol-gel process involving tetraethoxysilane in a polyamic acid solution, followed by thermal treatment [1][2][3]. Transparent and tough hybrid films with high silica contents were prepared using polyamic acid by conjugation to silica [4][5].…”