Effect of gold nanoparticle morphology on thermal properties of polyimide nanocomposite films

We have investigated effect of filler particle morphology on the thermal properties of polyimide (PI) nanocomposite films. Gold nanoparticles with various morphologies (non-aggregated, aggregated, and nanorod) were selected as model fillers. To prevent nanoparticle agglomeration in a solvent (1-methyl-2-pyrrolidinone), the surfaces of the gold nanoparticles were modified with triphenylphosphine-3,3',3 ''-trisulfonic acid trisodium salt (TPPTS), creating the surface sulfonic acid groups. Experiments showed that the thermal diffusivity of the films increased with a large aspect ratio (i.e., nanorod) or aggregation. The addition of gold nanoparticles could reduce the coefficient of thermal expansion (CTE) of PI films in all cases, and the CTE was lowest when the particle size was smallest (i.e., non-aggregated nanoparticles). By considering the effects of the thermal conductivity of the nanocomposite and the interfacial area between the nanoparticles and polymer matrix, we found that increasing the interfacial area between the nanoparticles and polymer matrix by controlling the nanoparticle morphology could reduce the CTE of the nanocomposite more effectively than increasing the thermal diffusivity of the nanocomposite.