Director dynamics in liquid-crystal physical gels.

Area of Science:

• Soft Matter Physics
• Polymer Science
• Liquid Crystals

Background:

• Nematic liquid-crystal (LC) elastomers and gels feature a polymer network linked to the nematic director.
• LC elastomers exhibit a single, non-hydrodynamic relaxation mode.
• Dynamic light scattering on LC gels reveals orientational fluctuations over a broad timescale.

Purpose of the Study:

• To investigate the distinct director dynamics in self-assembled liquid-crystal gels compared to LC elastomers.
• To elucidate the mechanisms behind the observed relaxation processes in LC gels.

Main Methods:

• Dynamic light-scattering studies were employed to probe orientational fluctuations.
• Analysis of relaxation dynamics across different timescales (short and long).

Main Results:

• LC gels display orientational fluctuations with both hydrodynamic (short times) and non-hydrodynamic (long times) behaviors.
• Long-time dynamics are anisotropic, increase with smaller scattering angles, and are attributed to director-network coupling.
• The network restructuring at longer times allows for complete decay of orientational fluctuations.

Conclusions:

• Director dynamics in self-assembled LC gels are fundamentally different from those in LC elastomers.
• LC gels exhibit soft orientational fluctuations at short times and at least two distinct relaxation processes.
• Coupling between the director and the polymer network significantly influences relaxation dynamics in LC gels.