A Unique Temperature-Induced Reverse Supramolecular Chirality-Assisted Gel-to-Gel Transition.

Abstract

Supramolecular hydrogels typically undergo a gel-to-sol transition with heat, as intermolecular interactions within the gel weaken. Although gel-to-gel transitions during heating are rare, they may occur due to minor rearrangements caused by thermal forces in the supramolecular self-assembled structure. Here, an unprecedented temperature-induced gel-to-gel transition assisted by supramolecular chiral inversion in a hydrogel system is presented. The transition results from a left-handed M-type helix to a right-handed P-type helix, attributed to the π-system-conjugated amino acid, l-Tyrosine (Fm- l-Tyr). Upon solvent dilution, Fm-l-Tyr induces translucent hydrogel formed by entangled fibers with a kinetically stable left-handed M-type supramolecular helix. At 70 °C, hydrogel transforms into an opaque gel with a reverse supramolecular chirality yielding a thermodynamically stable right-handed P-type helix. Supramolecular chiral inversion is substantiated by two chiroptical methods. This unique gel-to-gel transition, accompanied by chiral inversion, is anticipated to attract attention, especially for applications sensitive to chirality.