Polyimide/Graphene Nanocomposites with Improved Gas Barrier and Thermal Properties due to a Dual-Plane Structure Effect

Graphene nanosheets are prepared by solution-phase exfoliation of graphite and successfully incorporated with polyimide to obtain polyimide/graphene (DABPI/G) nanocomposites via in situ polymerization. Compared with those of pure DABPI, the DABPI/G nanocomposites exhibit better barrier and thermal properties. The oxygen and water vapor transmission rates of the DABPI/G (0.5 wt%) nanocomposite are 0.69 cm(3) m(-2) d(-1) and 0.44 g m(-2) d(-1), respectively, which are 92 and 85% lower than those of pure DABPI. Meanwhile, the DABPI/G (0.5 wt%) nanocomposite exhibits excellent thermal stability with a T-d5% of 578 degrees C and a coefficient of thermal expansion of -0.19 ppm K-1. The excellent barrier and thermal properties of DABPI/G nanocomposites are mainly attributed to the fine dispersion and orientation of the graphene nanosheets, increased crystallinity, and low free volume of the DABPI matrix. These are the result of the dual-plane structure effect, which is the synergistic orientation effect between the rigid planar molecular chains of DABPI and the nanosheets of graphene.