Polyurethane foam-supported three-dimensional interconnected graphene nanosheets network encapsulated in polydimethylsiloxane to achieve significant thermal conductivity enhancement

Polyurethane (PU) foams are widely used in thermal management materials due to their good flexibility. However, their low thermal conductivity limits the efficiency. To address this issue, we developed a new method to produce tannic acid (TA)-modified graphene nanosheets (GTs)-encapsulated PU (PU@GT) foams using the soft template microstructure and a facile layer-by-layer (L-B-L) assembly method. The resulting PU@GT scaffolds have ordered and tightly stacked GTs layers that act as three-dimensional (3D) highly interconnected thermal networks. These networks are further infiltrated with polydimethylsiloxane (PDMS). The through-plane thermal conductivity of the polymer composite reaches 1.58 W·m⁻¹·K⁻¹ at a low filler loading of 7.9 wt.%, which is 1115% higher than that of the polymer matrix. Moreover, the mechanical property of the composite is ∼2 times higher than that of the polymer matrix while preserving good flexibility of the polymer matrix owing to the retention of the PU foam template and the construction of a stable 3D graphene network. This work presents a facile and scalable production approach to fabricate lightweight PU@GT/PDMS polymer composites with excellent thermal and mechanical performance, which implies a promising future in thermal management systems of electronic devices.