Synthesis and Single Chain Fluorescence of a Sulfonated Conjugated Polymer

A water-soluble sulfonated conjugated phenylene vinylene polymer (Alt-Co-DPS-PPV) has been prepared by a Horner-Emmons reaction involving the condensation of a disulfonyl aryl bisphosphonate and terephthaldehyde. The photoluminescence from single chains of the polymer dispersed in a poly(vinyl alcohol) film at room temperature has been studied by confocal imaging techniques. Fluorescence intensity trajectories from Alt-Co-DPS-PPV single chains exhibit intermittencies or 'blinking' on both short (sub-millisecond) and long (seconds) time scales. The short time-scale intensity fluctuation data has been successfully analyzed using a simple model involving excursions from the fluorescent excited singlet state of the polymer chromophore to a non-emitting triplet state. It is found that the triplet state lifetime is molecule dependent and can be perturbed by the presence of the added heavy atom, iodide. These single chain fluorescence studies provide an insight into the distribution of excited state behaviours that make up the bulk polymer photochemical properties.