Triggering gel‐sol transition by weak magnetic field

Abstract

The self‐assembly of small and always chiral molecules into fiber‐like structures is a mysterious process, as the physics underlying such self‐assembly is unclear. The energy necessary for this process exceeds the one provided by common dispersion interactions and hydrogen bonding. The recent results obtained by the scientific group of Prof. Naaman from the Weizmann Institute of Science fed light on the nature of forces providing for the self‐assembly of chiral molecules and attributed these forces to spin‐exchange interactions. Therefore, the self‐assembly of chiral molecules should be magneto‐sensitive. We found such sensitivity in solutions of trifluoroacetylated ‐amino alcohols, and the process was inhibited by the magnetic field when fibers grew on the surface of the substrate. On the contrary, in bulk, the self‐assembly was enhanced by the magnetic field and led to the formation of a dense gel, while no gelation was observed in the absence of the external magnetic field. The latter observations are the theme of this short report, aimed to declare the effect itself but not pretend to describe it in full.

Magnetosensitivity of the Mercerization

“…Therefore, the magnetic field can affect the interaction of the helical molecules with the substrate, including the enantiospecific adsorption [29,30]. Moreover, the magnetic field can affect the interaction of the small chiral molecules with each other, either inhibiting their self-assembly on the surface of the substrate [31] or catalyzing the self-assembly in the bulk, providing for the true gelation of the solution [32].…”