Influence of the Polymer Matrix on the Optical Properties of Bioinspired Fluorescent Polymers Containing Diketopyrrolopyrrole Chromophores

Biodegradable and fluorescent polymer materials have attracted growing research interests due to their tunable properties and various applications such as bioimaging and photonic information technologies. Fluorescent materials obtained by physically blending polymers with organic fluorophores often face the problems of aggregation-caused quenching (ACQ) and photobleaching. We previously reported a series of bioinspired fluorescent polymers covalently linked with a single fluorophore in the middle of each polymer chain, reminiscent of the structure of fluorescent proteins. However, the impact of polymer matrices on the optical properties of these fluorescent polymers remains poorly understood. In this article, we report the influences of different polyesters, containing a common fluorophore of a red fluorescent diketopyrrolopyrrole (DPP) derivative in the middle of each polymer chain, on the optical absorption, fluorescence, and photostability of these polymers in different states, including dilute solutions in a good solvent such as tetrahydrofuran, colloidal nanoparticles in water, and solid films. We further demonstrate the applications of these polymers in the form of colloidal nanoparticles as contrast agents for the fluorescence bioimaging of cells.