Single molecule lifetime fluctuations reveal segmental dynamics in polymers.

Area of Science:

• Polymer Science
• Materials Science
• Physical Chemistry

Background:

• Amorphous polymers exhibit complex nanoscale segmental dynamics.
• Understanding these dynamics is crucial for designing functional polymers.
• Current methods often lack the resolution to probe these local rearrangements.

Purpose of the Study:

• To develop and apply a single molecule fluorescence technique to investigate nanoscale segmental dynamics in amorphous polymer matrices.
• To correlate observed fluorescence lifetime changes with local polymer density fluctuations.
• To quantify the number of polymer segments involved in local rearrangements.

Main Methods:

• Single molecule fluorescence spectroscopy was employed.
• Molecular lifetime trajectories of embedded fluorophores were recorded.
• Analysis focused on characteristic lifetime excursions and their relation to local polymer environment.

Main Results:

• Single fluorophore lifetime trajectories revealed peculiar excursions towards longer lifetimes.
• These asymmetric responses correlate with local density fluctuations in the polymer matrix.
• The number of polymer segments involved in local rearrangements decreased with increasing temperature for both poly(styrene) and poly(isobutylmethacrylate).

Conclusions:

• The developed single molecule fluorescence approach effectively probes nanoscale segmental dynamics.
• Local density fluctuations significantly impact photonic mode density and fluorescence lifetimes.
• This method offers a powerful tool for understanding molecular rearrangements in functional polymers.