Single molecule probing of dynamics in supercooled polymers

Area of Science:

• Polymer physics
• Single-molecule spectroscopy
• Materials science

Background:

• Understanding molecular dynamics in polymer matrices is crucial for material properties.
• Supercooled polymers exhibit unique dynamic behaviors.
• Single-molecule techniques offer high resolution for studying these dynamics.

Purpose of the Study:

• To investigate the rotational dynamics of single BODIPY molecules in a poly(methyl acrylate) matrix.
• To correlate molecular reorientation with polymer host dynamics.
• To characterize the nature of rotational jumps in the supercooled regime.

Main Methods:

• Single-molecule fluorescence experiments using pulsed excitation.
• Simultaneous measurement of fluorescence lifetime and linear dichroism time trajectories.
• Analysis of observables without data binning.
• Directly revealing rotational dynamics geometry from dichroism trajectories.

Main Results:

• Fluorescence lifetime correlations decay slightly faster than polarization correlations.
• This indicates the occurrence of large angular reorientations.
• Rotational dynamics analysis revealed both small and significantly larger rotational jumps.

Conclusions:

• The study elucidates the complex rotational dynamics of molecules within a supercooled polymer matrix.
• Both small and large angular jumps are essential for complete molecular reorientation.
• This provides insights into the interplay between guest molecule dynamics and polymer host behavior.