From Single Chains to Aggregates, How Conjugated Polymers Behave in Dilute Solutions

Abstract

Conjugated polymers offer unique combination of easily tailored mechanical, electrical and optical properties that makes them perfect materials for the preparation of various devices such as light-emitting diodes, photovoltaic cells or field-effect transistors. However, the design and fabrication of such devices in a controlled and reproducible way are possible only if the behavior and the properties of individual polymer chains are well understood. One major problem in this respect is that aggregation often occurs even in dilute solutions and prevents the single polymer chain studies. To address this issue, in this work we employed fluorescence correlation spectroscopy (FCS) to study the behavior of a model conjugated polymer, poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) in several commonly used solvents. The very high sensitivity of FCS allowed measurements in ultradilute solutions and thus unambiguous determination of the hydrodynamic radius of single polymer chains. The solvent...