On the relation of structure and dynamics in aromatic ring-tail structured liquids

Area of Science:

• Materials Science
• Physical Chemistry
• Soft Matter Physics

Background:

• Liquid phenylalkanes, composed of aromatic rings and alkyl chains, present a model system for studying competing molecular interactions.
• Understanding the interplay between molecular structure and dynamics is crucial in various liquid systems.

Purpose of the Study:

• To investigate the influence of competing ring-chain interactions on the structure and molecular reorientation in liquid phenylalkanes.
• To explore the formation of nanometer-scale structures and their impact on liquid dynamics.

Main Methods:

• Combined X-ray scattering and depolarized dynamic light scattering (DDLS) techniques were employed.
• X-ray scattering analyzed liquid structure, while DDLS probed molecular reorientation dynamics.

Main Results:

• X-ray scattering revealed a prepeak, indicative of nanometer-scale structuring, similar to ionic liquids, attributed to segregated ring and alkyl domains.
• The amplitude of this prepeak showed a transition in temperature dependence with increasing alkyl chain length.
• This transition correlated with changes in the activation energy for molecular reorientation observed via DDLS.

Conclusions:

• Phenylalkanes form nanostructured liquids, with ring-segregated domains influencing molecular dynamics.
• Ring-ring interactions dominate structure and dynamics for short alkyl chains but diminish with increasing chain length.
• This study serves as a proof of concept for investigating coupled structure-dynamics in liquids with weaker competing interactions.