Synchrotron x-ray diffraction study of liquid and glassy toluene

Area of Science:

• Physical Chemistry
• Materials Science

Background:

• Understanding the molecular arrangement in liquid and glassy states is crucial for materials science.
• Toluene's intermolecular structure influences its physical properties and phase transitions.

Purpose of the Study:

• To investigate the preferred intermolecular structures of toluene in liquid and glassy states.
• To analyze the temperature and annealing effects on toluene's molecular arrangement.

Main Methods:

• X-ray diffraction measurements of liquid and glassy toluene at various temperatures.
• Utilizing molecular dynamics simulations and reverse Monte Carlo methods for structural analysis.
• Employing a custom cryostat and high-energy X-ray diffractometer.

Main Results:

• The T-shaped intermolecular structure, not the parallel dimer, is preferred in both liquid and glassy toluene.
• The prevalence of T-shaped and side-by-side structures increases with decreasing temperature and annealing.
• Structural data (structure factor S(Q)) was successfully fitted for all measured states.

Conclusions:

• The T-shaped structure is a key feature of toluene's condensed phases.
• This finding may provide insights into the cooperatively rearranging regions proposed by Adam-Gibbs theory.
• The study highlights the importance of non-parallel packing in molecular liquids and glasses.