Mechanical Characterization of Stacked Single-Crystal of Polyethylene and Monolayer MoSe_2

摘要

Polymer single crystal (SC) is a key building block of semicrystalline polymers.However, direct experimental measurement of freestanding mono-lamellapolymer SC has not been demonstrated. This is, in large part, due to thedifficulties associated with manipulating freestanding individual monolamellaSC because of its extremely low rigidity and low robustness. Here, wedemonstrate a new strategy to successfully suspend and test a polymer SCby using a 2D material as backing. In particular, mono-lamella polyethylene(PE) SC is stacked on monolayer MoSe_2, and the hybrid stacks can besuspended over microholes. Nanoindentation is used to probe the suspendedPE-SC/MoSe_2 stacks and MoSe2 monolayers. The results suggest the firstexperimentally-measured in-plane moduli of PE-SC and 2D MoSe_2 as 32 ± 3 and237 ± 15 Gpa, respectively. Such a stacked unit represents an ultrathin structureof polymer-ceramic laminate and the idea can be applied to other laminatedcomposite systems. Therefore, this research will pave the way to accuratelymeasure the mechanical properties of polymer SCs and their composites, aswell as provide a key insight on designing composite structures.