Preparation and characterization of covalently functionalized graphene using vinyl‐terminated benzoxazine monomer and associated nanocomposites with low coefficient of thermal expansion

We describe the preparation of vinyl‐terminated benzoxazine‐functionalized graphene using free radical grafting. The resulting functionalized graphene (f‐graphene) was incorporated into bis(3‐allyl‐3,4‐dihydro‐2H‐1,3‐benzoxazinyl)methane (V‐BF‐a) monomer in order that nanocomposites could be prepared. Results of scanning electron microscopy and transmission electron microscopy revealed that the sheets of f‐graphene were well dispersed throughout the matrix, and there was a strong interfacial interaction between the f‐graphene and polyV‐BF‐a. The inclusion of f‐graphene into the nanocomposites resulted in a material with a high thermal stability and a low coefficient of thermal expansion (CTE); increasing the content of f‐graphene reduced the CTE significantly more. A reduction in the CTE of up to 48% was produced by adding just 1 wt% of f‐graphene; this corresponded to an increase of 12 °C in the glass transition temperature. These results suggest that f‐graphene nanocomposites can be ‘tuned’ to give materials with both a low CTE and a high thermal stability, and that graphene composites of this type can thus be manufactured to withstand a wider range of temperatures.