Nanocomposites of polyimide with Various Modified LDHs: Synthesis, characterisation and towards improvement of, morphology, thermal stabilities, mechanical properties, gas permeation and gas selectivity

Abstract

ABSTRACT Novel polyimide (PI) nanocomposite films were synthesised from diamine monomer (diamine 1B) and Pyromellitic dianhydride (PMDA) with various modified layered double hydroxides (LDHs) particles via solution intercalation polymerisation to poly(amic acid)s, followed by thermal imidization. Modified LDHs particles, including LDH-amino benzoate (M-LDHs) were prepared with the coprecipitation method. The intercalation of PI chains among the LDHs particles was examined using wide-angle X-ray diffraction (XRD) and electron microscopy (TEM) techniques. TEM photographs showed that most LDH layers were dispersed homogeneously into the matrix polymer on the nanoscale, although some particles of LDHs were agglomerated. Moreover, the addition of only a small amount of LDHs particles was enough to improve the thermal stabilities and mechanical properties of PI hybrid films. The thermo-optical properties were measured by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and ultraviolet-visible (UV–vis) spectrometry. As anticipated, though the gas permeability of pure gases, viz., He, N2, CH4 and CO2 exhibited decrease, it was not monotonous. A marked decrease in permeability of gases like CO2 and CH4, in comparison to relatively lower decrease in permeability of He was observed, especially at higher LDH loading. An increase in selectivity: α(He/CO2) and α(He/CH4), especially at higher LDH loading indicated the capability of nanocomposites to tune the selectivity favourably.