Synthesis of Fluorescently Labeled Polymers and Their Use in Single-Molecule Imaging

A series of linear polymers labeled with one perylene diimide per polymer chain were synthesized using living free-radical polymerizations based on nitroxides. Depending on the choice of the initiator, the perylene diimide was either at the end or the middle of the polymer chain. The polymers were synthesized as homopolymers or block copolymers from butyl acrylate, styrene, isoprene, and butadiene. Poly(butadiene) labeled with a perylene diimide dye in the center of the polymer was studied using single-molecule imaging in a poly(methyl methacrylate) host. Most of the dyes remained stationary during the experiments, but approximately 5% of the dyes reoriented. The fraction of dyes reorienting was observed to be independent of pumping intensity. This system is an excellent test bed for studying the local environment of the dye and the heterogeneity of the host polymer.