(376ax) Understanding Temperature-Induced Self-Folding of Thermo-Sensitive Polymer Grafted Graphene

Physical and chemical properties of 2D materials like graphene are strongly affected by changes in their shape through the introduction of curvature, wrinkling, and folding. Graphene sheets can be folded to form 3D structures by grafting thermo-sensitive polymers to its surface and by changing the temperature. In this study, we attempt to unravel the mechanism of graphene self-folding by conducting coarse-grained (CG) molecular dynamics (MD) simulations of poly(N-isopropylacrylamide) (PNIPAM) grafted graphene models. PNIPAM is a classing thermo-sensitive polymer with a lower critical solution temperature (LCST) of 305 K. Below and above its LCST PNIPAM is in a coil-like and globule-like state. MD simulations were carried out below (290 K) and above (320 K) the LCST of PNIPAM in an aqueous medium. The CG MD simulations were performed at different grafting densities, coverages, and arrangements of the PNIPAM chains on the graphene surface. The simulation trajectories were analyzed to investigate the mechanism of graphene folding induced by coil-to-globule conformation changes of PNIPAM. The study further demonstrate possibilities of controlling the graphene folding to generate specific 3D structures.