Single molecule demonstration of Debye-Stokes-Einstein breakdown in polystyrene near the glass transition temperature.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 35739122.
- Also identified by DOI 10.1038/s41467-022-31318-z and PMC identifier 9226357.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Rotational-translational decoupling, in which translational motion is apparently enhanced over rotational motion in violation of Stokes-Einstein (SE) and Debye-Stokes-Einstein (DSE) predictions, has been observed in materials near their glass transition temperatures (T<sub>g</sub>). This has been posited to result from ensemble averaging in the context of dynamic heterogeneity. In this work, ensemble and single molecule experiments are performed in parallel on a fluorescent probe in high molecular weight polystyrene near its T<sub>g</sub>. Ensemble results show decoupling onset at approximately 1.15T<sub>g</sub>, increasing to over three orders of magnitude at T<sub>g</sub>. Single molecule measurements also show a high degree of decoupling, with typical molecules at T<sub>g</sub> showing translational diffusion coefficients nearly 400 times higher than expected from SE/DSE predictions. At the single molecule level, higher degree of breakdown is associated with particularly mobile molecules and anisotropic trajectories, providing support for anomalous diffusion as a critical driver of rotational-translational decoupling and SE/DSE breakdown.