Preparation and properties of polyimide nanocomposites with negative thermal expansion nanoparticle filler

Nanocomposites with tunable coefficient of thermal expansion (CTE) were prepared by incorporating cubic zirconium tungstate (ZrW2O8) nanoparticles at various volume percentages in a polyimide (PI). Rod-shaped nanoparticles of cubic ZrW2O8, which has isotropic negative thermal expansion, were synthesized using a hydrothermal method. The interfacial interaction between the PI and ZrW2O8 was enhanced by covalently bonding different organic moieties, including a short aliphatic silane and PI oligomer, to the surface of ZrW2O8. Structure–property relationships for the PI–ZrW2O8 nanocomposites were investigated for thermal degradation, glass transition, tensile and thermal expansion properties. Addition of ZrW2O8 nanoparticles did not alter the thermal degradation and glass transition temperature of the base PI. The addition of ZrW2O8 nanoparticles increased the Young's modulus of the polymer, indicating stiffening of the polyimide matrix. The increase was higher for nanocomposites with engineered interfaces due to the efficient load transfer achieved through the presence of linker groups. The addition of ZrW2O8 reduced the in-plane CTE of the base PI at all loadings studied. The CTE of the base PI was reduced by around 22% with the addition of ZrW2O8 at 15 volume% loading. -- Highlights: ► Polyimide nanocomposites with nanoparticles of zirconium tungstate were prepared. ► Effect of surface functionalized ZrW2O8 on properties of nanocomposites is reported. ► Polyimide–ZrW2O8 nanocomposites exhibit reduced CTE and increased tensile modulus. ► The CTE of polyimide is reduced by 22% with the addition of 15 volume% ZrW2O8. ► Surface functionalization of filler improves the tensile properties of composites.