To study self-assembly of 2C 18 @OPP from a dynamic perspective, we conducted a 2000 fs MD simulation at 300 K in a periodic box, the center of mass of OPP is fixed at box center while the position of the two C 18 molecules are randomly placed in the vacuum region. From MD trajectory ("Molecular self-assembly animation" in Supplemental Material), it is found that the self-assembly of C 18 into OPP can be divided into three stages, namely wander, adsorption, and equilibrium. The first C 18 (C 18 -1), which was wandering in vacuum at the beginning, soon encounters OPP at about 200 fs (Figure ). After that, C 18 -1 first briefly tilts to adsorb on the inner wall of the loop to form a metastable state. The inclined adsorption of C 18 to the edge of OPP is apparently caused by the π-π stacking effect between the out-of-plane π orbital of C 18 and the (out-of-plane) π orbital of phenyl ring in OPP, which is bound to be disrupted by molecular thermal motion due to the imperfect match in size of C 18 and phenyl ring. Then, C 18 -1 flips in the loop to make its center coincide with the loop center and forms a stable configuration. The angle between the plane of C 18 -1 and that of the loop it resides in this equilibrium stage fluctuates in the range of 0 to 20°, that is, the orientation of the complexed C 18 basically remains parallel to the loop. The binding of the second C 18 (C 18 -2) to OPP also experiences the aforementioned three self-assembly stages, but the whole process clearly takes much longer (Figure ).