Effect of Covalent Functionalization on Thermal Transport across Graphene–Polymer Interfaces

Abstract

This Article is concerned with the interfacial thermal resistance for polymer composites reinforced by various covalently functionalized graphene. By using molecular dynamics simulations, the obtained results show that the covalent functionalization in graphene plays a significant role in reducing the graphene−paraffin interfacial thermal resistance. This reduction is dependent on the coverage and type of functional groups. Among the various functional groups, butyl is found to be the most effective one in reducing the interfacial thermal resistance, followed by methyl, phenyl, and formyl. The other functional groups under consideration such as carboxyl, hydroxyl, and amines are found to produce negligible reduction in the interfacial thermal resistance. For multilayer graphene with a layer number up to four, the interfacial thermal resistance is insensitive to the layer number. The effects of the different functional groups and the layer number on the interfacial thermal resistance are also elaborated using the vibrational density of states of the graphene and the paraffin matrix. The present findings provide useful guidelines in the application of functionalized graphene for practical thermal management.

Diamond Nanothread as a New Reinforcement for Nanocomposites

“…[ [24][25][26] To study this effect, we randomly replaced 5% of the DNT-2's surface H atoms by -C 2 H 5 molecules. It is found that the total vdW energy change increased from ~ 10.5 eV to ~ 12.5 eV due to the presence of the -C 2 H 5 functional groups, which corresponds to about 20% increase in ISS (from ~ 58 MPa to ~ 68 MPa).…”

Investigating thermal conductivities of functionalized graphene and graphene/epoxy nanocomposites

“…2(a and b), were randomly distributed for the smallest length (50 Å) and then repeated to generate the desired simulation cells of FG. These two functional groups were considered because they are commonly observed in FG [11]. In addition, to graft the functional groups to the graphene surface, the hybridization was changed from sp 2 to sp 3 .…”

“…The MD simulations were conducted using a large-scale atomic/molecular massively parallel simulator (LAMMPS) [18], and the interatomistic behaviors were described according to the polymer consistent force field (PCFF) potential [19]. Because the PCFF potential has been employed to model the mechanical properties of graphene and epoxy resin accurately [11,20,21], in this study, the PCFF potential was utilized to characterize the properties of graphene and graphene/epoxy nanocomposites. The functional form of the PCFF potential is expressed according to the summation of bonded and nonbonded energy.…”

“…In addition, direct characterization of the ITC of the graphene/matrix interface is essential for understanding the mechanism of interfacial thermal transport and the enhancement of nanocomposite thermal conductivity. Therefore, the influences of functional groups on the ITC have been investigated using molecular dynamics (MD) simulation [9][10][11][12][13]. Wang et al [9] examined the ITC in graphene/polyethylene (PE) nanocomposites and indicated that grafting PE chains to the graphene surface can effectively improve the ITC as well as the vibrational coupling between the graphene and polymer.…”

“…Luo and Lloyd [10] examined thermal energy transport across the graphene polymer interface and demonstrated that forming covalent bonds at the interface can improve the thermal transport properties of nanocomposites. Wang et al [11] characterized the effect of the grafting density of functional groups on the ITC of graphene nanocomposites and indicated that increasing the grafting density of functionalization can enhance the interfacial thermal transport properties. Shen et al [12] evaluated the vibrational power spectrum of functionalized graphene (FG) and epoxy and demonstrated that the extent of vibrational coupling between the graphene and epoxy can be improved by the functional groups.…”