Thermal conductivity and structure of non-covalent functionalized graphene/epoxy composites

Non-covalent functionalization was used to functionalize graphene nanosheets (GNSs) through π–π stacking of pyrene molecules with a functional segmented polymer chain, which results in a remarkable improvement in the thermal conductivity of GNS-filled polymer composites. The functional segmented poly(glycidyl methacrylate) containing localized pyrene groups (Py-PGMA) was prepared by atom transfer radical polymerization, and Py-PGMA was characterized by nuclear magnetic resonance spectroscopy. Raman spectra, X-ray photoelectron spectroscopy and thermogravimetric analysis reveal the characteristics of Py-PGMA–GNS. Differential scanning calorimetry indicated that the functional groups on Py-PGMA–GNSs can generate covalent bonds with the epoxy matrix, and further form a cross-linked structure in Py-PGMA–GNS/epoxy composites. The Py-PGMA on the GNS surface not only plays an important role to facilitate a homogeneous dispersion in the polymer matrix but also improves the GNS–polymer interaction, which results in a high contact area. Consequently, the thermal conductivity of integrated Py-PGMA–GNS/epoxy composites exhibited a remarkable improvement and is much higher than epoxy reinforced by multi-walled carbon nanotubes or GNSs. The thermal conductivity of 4 phr Py-PGMA–GNS/epoxy has about 20% (higher than that of pristine GNS/epoxy) and 267% (higher than pristine MWCNT/epoxy).