Incorporation of titanate nanosheets to enhance mechanical properties of water-soluble polyamic acid

Pyromeliticdianhydride (PMDA) and 4’,4’-oxydianiline (ODA) were used asmonomers of polyimide. To synthesise a water soluble polyimide precursor (polyamic acidsalt), triethylamine (TEA) was added to polyamic acid with a TEA/COOH mole ratio of 1:1.Titanate nanosheets were synthesised by solid-state reaction, ion-exchanged with acid, andexfoliated by TEA. Exfoliated titanate nanosheets were mixed with water soluble polyamicacid salt as reinforcing filler. Drop casting was deployed to synthesise polyamic acid/titanatenanosheet nanocomposite films. Scanning electron microscopy (SEM) and transmissionelectron microscopy (TEM) were employed to study the morphology and dispersion ofnanosheets in the colloidal dispersion and the solid film composite. Modulus and hardness ofnanocomposites was provided by nanoindentation. Hardness increased by 90% with addition of2% TiNS while modulus increased by 103% compared to pure polymer. This behaviour agreeswell with Halpin-Tsai theoretical predictions up to 2 wt% filler loading; agglomeration occursat higher concentrations.