Direct measurement of the end-to-end distance of individual polyfluorene polymer chains

Wide-field imaging of individual multichromophoric molecules and successive photobleaching were used to determine, accurately, the relative position of the chromophores in such systems. First, a polyphenylene dendrimer with well-defined geometry was used to establish the accuracy in localization that can be obtained by this methodology. For a signal-to-noise ratio of 20, interchromophoric distances could be measured with 4 nm accuracy. Next, the method was used to determine the end-to-end distribution of an end-capped polyfluorene polymer. From comparison between the experimental and simulated distributions, information on the conformation of the polymer could be deduced. It was found that the polymer has a nonlinear conformation. A conjugation length of six monomer units gave the best fit of the experimental data to the proposed model.