A Study on the Interfacial Compatibility, Microstructure and Physico-Chemical Properties of Polyimide/Organically Modified Silica Nanocomposite Membrane.

Md A Wahab,Shazed Aziz,Mohammad R Karim,Muhammad O Aijaz,Abu A I Sina,Bidita Salahuddin

doi:10.3390/polym13081328

Abstract

Polyimide-silica (PI-Silica) composites are of tremendous research interest as high-performance materials because of their excellent thermal and mechanical properties and chemical resistance to organic solvents. Particularly, the sol-gel method of fabricating such composites is popular for manipulating their properties. In this work, PI-silica composite films are synthesized by the sol-gel method and thermal imidization from the solution mixtures of hydrolyzed tetraethoxysilane (TEOS) (or glycidoxypropyltrimethoxysilane (GPMS)) modified silica and an aromatic polyamic acid (PAA) based on 3,3′,4,4′-biphenyl tetracarboxylic dianhydride (BPDA)–p-phenylenediamine (PDA). The phase morphology of composites is found to be controlled by the substitution of TEOS with GPMS. Solid-state NMR spectroscopy is used to confirm the structural components of silica and GPMS-modified silica, whereas FT-IR results confirm the complete imidization of polyimide and composite film and suggest successful incorporation of Si–O–Si bonds into polyimide. The thermal, optical transmittance, and dielectric constant characterizations of pure polyimide and composite films are also carried out. Thermal stability of pure polyimide is found to be increased significantly by the addition of silica, whereas the partial substitution of TEOS with GPMS decreases the thermal stability of the composite, due to the presence of the alkyl organic segment of GPMS. The optical transmittance and dielectric constant of the composite films are controlled by manipulating the GPMS content.

Highlights

Polyimide (PI) materials exhibit outstanding physico-chemical, electrical, and mechanical properties that allow them to be used in several advanced applications such as microelectronic, packaging, and separation [1,2,3,4,5,6,7,8]
The Si-O bonds in the silica network are usually defined as Qn and Tn sites, where the presence of Qn type is due to the formation of pure silica network and Tn -type is formed from the organosilica type material such as GPMS
The substitution of TEOS with GPMS can reduce the formation of large silica particles by using a large number of hydroxyl groups and can form H-bonds with anhydride, carbonyl, carboxyl, and terminal amine groups in the polyimides/polyamic acids

Summary

Introduction

Polyimide (PI) materials exhibit outstanding physico-chemical, electrical, and mechanical properties that allow them to be used in several advanced applications such as microelectronic, packaging, and separation [1,2,3,4,5,6,7,8]. It is found that the addition of reinforcing filler into the PI matrix has shown to provide such desirable properties These composites with interesting synergistic properties have received much attention from both academics and industries. The type of silica fillers (either organosilica/inorganic) can control the compatibility and thermo-mechanical properties of the final PI matrix. The resulting composite with large phase separation is found to deteriorate the thermomechanical properties instead of enhancement [22,23,24] To address this problem, Akter et al [25,26] have reported the polyimide-silica composites, in which the newly synthesized oligomeric species 2,6-bis(3(triethoxysilyl)propyl)pyrrolo[3,4-f]isoindole-1,3,5,7(2H,6H)-tetraone (APA) was used as a coupling agent to improve compatibility between organic and inorganic phases.

Methods

Results

Conclusion