Functionalization of molecular glasses: effect on the glass transition temperature

Abstract

Molecular glasses constitute an appealing class of materials combining the advantages associated with small molecules with the potential to form glassy phases. However, the current design of functional molecular glasses is highly dependent on a trial and error approach. By achieving a better understanding of the microscopic behaviors that govern the propensity of a system to generate a glassy state, the glassy behavior of new molecules can be identified before their synthesis. Full-atomistic simulation is genuinely invaluable for achieving this goal. A series of functionalized triazine-based molecular glasses previously synthesized and characterized were thus used as models to carry out simulations. To estimate the link between microscopic calculations and macroscopic properties, mechanical equilibrium and isotropy have first to be achieved. The reproducibility of the simulation results and their linear correlations with experimental data are two essential criteria for corroborating the validity of our method. Mobility of the core and the functional “headgroups” can then be interpreted, rationalizing the effect of molecular structure on the formation of glasses, and on the important differences in T_g observed for this series of compounds.