Diffusion of Molecular and Macromolecular Polyolefin Probes in Cylindrical Block Copolymer Structures As Observed by High Temperature Single Molecule Fluorescence Microscopy

Abstract

Highly sensitive fluorescence microscopy methods allow for the observation of single bright fluorescent probes. Analysis of their trajectories gives access to the mode of diffusion and the heterogeneity in motion of individual probes. Especially for structured soft materials, this information is of paramount importance for a multitude of possible applications such as nanoelectronics, nanophotonics, or nanomembrane technology. Compared to biological systems, utilization for materials research faces the challenge that relevant processes occur at elevated temperature, often above 100 °C, and that fluorescence labeling procedures are yet less evolved. We investigated the motion of single probes in block copolymer morphologies from room temperature to over 100 °C with a custom-made heating device to allow for such high temperatures without damaging the optics of a commercial optical microscope and also with the possibility to measure under a nitrogen atmosphere to reduce photobleaching of the dyes. Apart from tracking single perylenediimide derivative as a molecular probe, we labeled polyolefin chains with this chromophore and observed their diffusion. For the synthesis of the polyolefins, as the most important class of polymeric materials in general, we present a protocol that provides high quality samples in terms of molecular weights, molecular weight distributions, and proven degree of dye functionalization. The dependency of temperature, block copolymer composition, and probe size on the diffusion behavior is elaborated.