Graphene (single layer) is well known for its outstanding thermal conductivity. Despite the exploitation of graphene in bulk materials is still very much limited by its availability, graphene-related materials (GRM) such as multi-layer graphene (MLG), reduced graphene oxides (RGO) and graphene nanoplatelets (GNP) are currently of high interest for the exploitation in thermally conductive materials. On the other hand, there is an increasing interest and need for thermally-conductive polymer-based materials, allowing the manufacturing of a range of heat exchangers, taking advantage of the corrosion resistance and ease of processing typical of polymers. While the combination of polymers and graphene-related materials into nanocomposites is obvious, the performances obtained are strongly limited by the defectiveness GRM, the nanoparticles dispersion/assembly and the inefficiency of the contacts between GRM within the percolating network.<br/>The first part of this talk will deal with the preparation and properties of thermally conductive nanocomposites prepared via ring-opening polymerization during melt mixing of cyclic oligomers of polybutylene terephthalate (CBT) in the presence of several grades of RGO and GNP, having variable size and structural defectiveness. Nanocomposites thermal conductivity was correlated with both GRM structural defectiveness and their degree of dispersion in the polymer matrix.<br/>The second part of the talk will deal with the design and synthesis of molecular junctions between GRM to create nanopapers with inherently low contact thermal resistance among nanoparticles. Molecular dynamics was used to screen for candidate molecules to enhance conductance at the particle-particle contacts, including junctions length and structure (aliphatic vs aromatic). Covalent and non-covalent synthetic approaches were exploited to engineer contact resistance in graphene networks. Covalent functionalization was demonstrated to enhance both in-plane and cross-plane thermal conductivity of GNP networks. Non-covalent functionalization by the use of bispyrene derivatives to build supramolecular junctions between nanoplatelets was also observed to strongly influence the heat transfer on the network, also depending on the chain length of the alkyl spacer between pyrene groups.<br/>Finally, impregnation of GRM nanopapers with polydimethyl siloxane will be presented, as a facile method to obtain highly flexible and tough thermally conductive nanocomposites.<br/>

Thermally conductive graphene-based polymer nanocomposites: Nanoparticles quality and controlled assembly to enhance heat transfer efficiency

2019 Spring National Meeting

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