A water-soluble conjugated polymer brush with multihydroxy dendritic side chains

Abstract

A brush-like water-soluble conjugated polymer bearing a poly[9,9′-dihexylfluorene-co-alt-4,7-(2,1,3-benzothiadiazole)] (PFBT) backbone and multihydroxy hyperbranched polyglycerol (HPG) side chains is facilely synthesized by combination of “grafting from” strategy and the ring-opening polymerization (ROP) technique. The PFBT-g-HPG brush shows bright fluorescence in water with an emission maximum at 587 nm and a quantum yield of 15%. Laser light scattering (LLS), transmission electron microscopy (TEM) and atomic force microscopy (AFM) analyses reveal that PFBT-g-HPG adopts a spherical shape in water and a wormlike conformation in N,N-dimethylformamide (DMF). PFBT-g-HPG shows stable fluorescence against the variation of pH and ionic strength as well as interference of biomolecules. MCF-7 cancer cell imaging results show that the PFBT-g-HPG exhibits low cytotoxicity and high photostability, which allows fluorescence imaging in a high contrast manner. On the basis of the numerous hydroxyl groups of the grafted HPG, post-functionalization of PFBT-g-HPG could afford various PFBT-g-HPG-based brushes with adjustable surface functionality (e.g., carboxylic groups) and solubility. This study thus provides a versatile brush approach to water-soluble conjugated polymers for advanced sensing and imaging applications.