Revealing different aggregational states of a conjugated polymer in solution by a nanopore sensor

Abstract

The functionalities of conjugated polymers are determined not only by local molecular structure, but also by the mesoscale conformational and morphological states of the polymer chains. Simulation studies have successfully established the connections between molecular structure and conformational states of certain conjugated polymers. However, experimental tools that can accurately discriminate between different conformational and morphological states of conjugated polymers are still scarce. Here, we use a nanopore sensor to analyze different aggregational states of a polythiophene derivative by threading the polymer through the pore under applied potentials. When the fluorescence of the polythiophene is quenched by pH tuning or the presence of Dy³⁺, the UV-vis and fluorescence spectra of the two solutions appear indistinguishable. However, threading the polymer molecules of these two solutions through an α-hemolysin nanopore affords entirely different translocation profiles owing to their different aggregational states. We further substantiate the results by conducting aggregational interconversion experiments and TEM measurements. This work has clearly indicated that nanopores are promising tools for the analysis of aggregational changes of conjugated polymers and may open new avenues for the investigation of aggregational states of biomacromolecules in the context of early disease diagnosis and prognosis.