Self-Propelled Motion Sensitive to the Chemical Structure of Amphiphilic Molecular Layer on an Aqueous Phase.

Two novel amphiphiles, -(3-nitrophenyl)stearamide (MANA) and ,-(4-nitro-1,3-phenylene)distearamide (OPANA), were synthesized by reacting nitroanilines with one or two equivalents of stearic acid. We investigated how the molecular structures of these compounds influenced the characteristics of a self-propelled camphor disk placed on a monolayer of the synthesized amphiphiles. Three types of motion were observed at different surface pressures (): continuous motion ( < 4 mN m), deceleration (4 mN ≤ ≤ 20 mN m), and no motion ( > 20 mN m). The speed of the motion of the camphor disks was inversely related to for both MANA and OPANA at the temperatures tested, when increased in the respective molecular layers under compression. The spectroscopic evidence from UV-Vis, NMR, and ESI-TOF-MS revealed that the dependence of the speed of the motion on originates from the intermolecular interactions that are present in the monolayers. This study suggests that it is possible to control the self-propelled motion by manipulating contributing factors at the molecular level.