| Abstract
| - Molecular self-aligning of amphiphilic molecules into bundles with a constant width of 7−13 nm was observedunder tapping-mode atomic force microscopy (TM-AFM). The requisite amphiphile, a poly(oxypropylene)-trimelliticamido acid sodium salt, is constituted of a symmetric amido acid structure with potential noncovalent forces of ioniccharges, hydrogen bonds, π−π aromatic stacking, and hydrophobic interactions for intermolecular interaction. Theamphiphiles are able to self-align into orderly hierarchical assemblies after simply being dissolved in water and driedunder spin-coated evaporation. Under the TM-AFM tapping process, the bundles increased their length from an initial20 to 600 nm. A sequential TM-AFM scanning and interval heating process was designed to probe the morphologicaltransformations from the molecular bundles to lengthy strips (nearly micrometer scale) and to columns (with 5−7nm spacing between the parallel strips). The formation of hierarchical arrays via molecular stretching, aligning, andconnecting to each other was simultaneously observed and accelerated under the TM-AFM vibration energy. Themolecular self-alignment caused by vibrations is envisioned to be a potential methodology for manipulating moleculesinto assembled templates, sensors, and optoelectronic devices.
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