Studying Pyrene-Labeled Macromolecules with the Model-Free Analysis

The model-free (MF) analysis was applied to the fluorescence decays of 32 pyrene-labeled macromolecules to probe their internal dynamics. Depending on whether a pyrene derivative was attached to the chain ends of a linear chain, randomly along a polymer backbone, or at the chain terminals of dendrimers, the MF analysis was applied to probe the dynamics of polymer ring closure, backbone flexibility, or chain terminal mobility, respectively. For those polymeric constructs whose decays could be fitted according to Birks' scheme or the fluorescence blob model (FBM), good agreement was obtained between the rate constant for excimer formation retrieved from the MF analysis and those obtained according to the Birks' scheme or FBM analyses. The MF analysis was also applied to conduct the first successful direct comparison of the chain terminal dynamics of two types of pyrene end-labeled dendrons. Finally, the MF analysis was employed to build a calibration curve against which the internal dynamics of any pyrene-labeled macromolecule can now be benchmarked. This study further confirms the versatility and robustness of the MF analysis to study any type of pyrene-labeled macromolecule.