A molecular dynamics study on the effect of TSW defective graphene on the glass transition temperature of polymer materials

Molecular models of pristine graphene (GN) and GN with Thrower–Stone–Wales (TSW) defect-reinforced polymethyl methacrylate (PMMA) composites were established. The pure PMMA matrix was developed as a benchmark to study the effect of TSW defective GN (TSW-GN) on the glass transition temperature (Tg) of PMMA composites based on molecular dynamics simulations. The Tg values of these composites were obtained by fitting the scatter plots of the temperature versus the specific volume of the models. The results showed that the introduction of TSW defects can effectively increase the Tg of the PMMA composites. Additionally, the Tg of the PMMA composites gradually increased with an increase in TSW defects on the GN surface. The interaction energy between the TSW-GN and PMMA matrix, the density distribution of PMMA, the mean square displacements of the PMMA chains, and the free volume of these models were analyzed to understand the internal mechanisms with respect to the variations in the Tg from an atomic perspective. It can be concluded that the appropriate introduction of TSW-GN can improve the upper limit of the applied temperature of PMMA composites. In addition, guidance for the use of TSW-GN in different application environments of polymer composites was proposed.