Heads or tails: how do chemically substituted fullerenes melt?

Area of Science:

• Materials Science
• Physical Chemistry
• Chemical Physics

Background:

• Chemically substituted fullerenes are advanced materials with unique properties.
• Understanding their phase transitions, like melting, is crucial for material applications.
• The molecular mechanisms driving these transitions remain an active area of research.

Purpose of the Study:

• To determine whether the fullerene moiety or the substituted group drives the melting process in substituted fullerenes.
• To investigate the temperature-dependent dynamics of phenyl-C61-butyric acid methyl ester.
• To quantitatively compare experimental data with molecular dynamics simulations.

Main Methods:

• Quasielastic neutron-scattering experiments were conducted across a range of temperatures.
• Classical molecular-dynamics simulations were performed on phenyl-C61-butyric acid methyl ester.
• Dynamic structure factors were calculated from simulation trajectories and convolved with instrument response for direct comparison.

Main Results:

• Melting in this fullerene derivative is exclusively driven by temperature-activated motions of the substituted tail.
• Quantitative estimates for the activation energy of melting were determined.
• The study identified distinct phase transitions: a plastic-crystalline phase followed by a liquid phase.

Conclusions:

• The dynamics of the substituted tail are the primary factor governing the melting of chemically substituted fullerenes.
• This finding provides critical insights into the phase behavior of fullerene derivatives.
• The methodology enables precise comparison between experimental scattering data and molecular dynamics simulations.