Zirconium tungstate (ZrW2O8)/polyimide nanocomposites exhibiting reduced coefficient of thermal expansion

ZrW2O8 is obtained as microparticulate powder following traditional methods or as nanoparticulate powder using an inverse micelle sol-gel synthesis strategy. As-prepared ZrW2O8 powders, surface-derivatized with (3-aminopropyl)siloxy linker molecules, disperse well in BTDA-ODA polyamic acid resins to give thermally cured ZrW2O8/polyimide hybrid films showing good wetting of embedded ceramic particles. Measured CTE values of ZrW2O8/BTDA-ODA hybrid films containing 0-50 wt % (0-22 vol %) ceramic loading show a controlled reduction in thermal expansion with increasing ceramic content. Reduction in CTE is modeled best assuming mixed-law behavior with incorporation of an interfacial phase region. A 22 vol % ceramic loading gives a 30% (10 ppm/K) reduction of CTE. ZrW2O8/BTDA-ODA films containing 0.8 vol % (3 wt %) ceramic loading exhibit unusually low thermal expansion, although the significance of this observation remains to be confirmed.