Preparation and properties of core-shell silver/polyimide nanocomposites

A new series of core-shell structured silver/polyimide (PI) nanocomposites was prepared by in situ polymerization followed by the chemical imidization of poly(amic acid) (PAA, precursor of PI) at a low temperature. The TEM images showed that the silver cores of the nanocomposites were encapsulated with homogeneous shells with thickness of 4 and 8 nm at silver contents of 90 and 60 %, respectively. The shell thickness was controlled by varying the content of PAA. FTIR spectroscopic analysis indicated that the imide ring formation occurred after the chemical imidization. The Ag/PI nanocomposites showed excellent thermal stability and exhibited only 10 % weight loss at 300 A degrees C in the air. Moreover, percolation was observed at silver weight fractions close to the critical value, and the maximum dielectric permittivity of the nanocomposites was 120, which is about 40 times higher than that of pristine PI.