Preparation of thermostable PBO/graphene nanocomposites with high dielectric constant.

In this study, poly(p-phenylene benzobisoxazole) (PBO)/graphene composites were prepared using PBO and poly(4,6-dihydroxymetaphenylenediamine terephthalamide) (PHA)-modified graphene oxide (GO-PHA). PHA is the precursor of PBO. GO-PHA was obtained via chemical coupling reaction of amino-terminated PHA and acyl-chloride-functionalized GO. Partially reduced graphene nanosheets and benzoxazole rings were formed after heating. GO-PHA could be stably dispersed in methane sulfonic acid (MSA), which facilitated its uniform distribution in the PBO matrix. The PBO/graphene nanocomposites were obtained by the dissolution of GO-PHA and PBO in MSA. The thermogravimetric analysis results showed that the PBO/graphene composites had good thermal stability below 400 degrees C. The dielectric constant of the composites increased as the amount of GO-PHA increased, and the percolation threshold was f(c) = 0.037. The nanocomposite had a dielectric constant of 15.8, which was approximately five times larger than that of pure PBO polymer.