Precisely tailoring the thermodynamic compatibility between single-walled carbon nanotubes and styrene butadiene rubber via fully atomistic molecular dynamics simulation and theoretical approach

Abstract From the perspective of thermodynamics, the compatibility between filler and matrix determines the dispersion and morphology of filler and further determines the final properties of composites. At present, it is difficult to obtain a quantitative relationship between the surface chemistry of filler and compatibility with matrix through experimental means. In this study, the quantitative relationship between functional groups and Hildebrand (δT) and two-component solubility parameters (δvdW, δele) of single-walled carbon nanotubes (SWCNTs) was obtained by molecular dynamics (MD) simulation. The most notable conclusion is that with the increase of grafting ratio, the δT and δvdW of SWCNTs first decrease, reach a minimum and then increase. This regularity makes the SWCNTs with different functional groups exhibit different compatibility behaviors with styrene butadiene rubber (SBR), resulting in different functionalization principles for different groups. Two-component solubility parameters of SWCNTs and SBR were further proved to be able to predict well their compatibility by Flory-Huggins model. Each functional group has the optimum grafting ratio at which the compatibility is the best. Additionally, the –CH3, –CH(O)CH– and –OH functionalized systems exist the optimum temperature for the best compatibility. The multifunctional groups is superior to a single group for the compatibility. This study provides a quantitative guidance for the functionalization of SWCNTs towards the good compatibility with SBR.