Given that C 18 @OPP and 2C 18 @OPP formed by C 18 and OPP have been shown to be stable and the energy barrier of relative rotation between host and guest molecules is very small, MD simulations of the self-assembly process and rotational behavior of the 2C 18 @OPP are particularly interesting. Because ab-initio MD simulation is too expensive for the system under study, the simulations were conducted based on classical molecular force field (FF). Relevant technical details, as well as the movies of the MD trajectory of self-assembly and rotation of 2C 18 @OPP have been provided in Supplemental Material.