On-Surface Non-Equilibrium Phase Evolution Toward 2D Supramolecular Glass.

Abstract

Controlling crystalline-to-glassy transitions represents a vibrant frontier in supramolecular chemistry and condensed matter physics, providing fundamental insights into non-equilibrium dynamics and enabling functional tunability for elasticity electronics and phase-change devices. Conventional two-dimensional (2D) supramolecular assembly follows an enthalpy-dominated thermodynamic paradigm, restricting the exploration of non-equilibrium supramolecular glasses (SMGs). Herein, we report the controlled construction of a non-equilibrium SMG on Ag(111) using in situ-generated triradical triphenyl-triazine molecules. The electrophilic triazine core enriches charge density at radical sites and strengthens molecule-substrate interfacial coupling, imposing pronounced kinetic constraints at the surface. Upon thermal activation, the system follows a non-monotonic, four-phase evolution that involves a thermodynamically uphill transformation. Rather than directly relaxing to the global thermodynamic minimum, it is kinetically arrested into a metastable glassy state with short-range order and long-range disorder. This work revises the conventional enthalpy-dominated view of supramolecular assembly and establishes a backbone-modulated radical kinetic strategy for rational fabrication of disorder-tunable 2D supramolecular materials.