Improving photophysical properties and hydrophily of conjugated polymers simultaneously by side-chain modification for near-infrared cell imaging

Conjugated polymers (CPs)-based near-infrared phototheranostics are receiving increasing attention due to their high molar extinction coefficient, wide emission wavelength, easy preparation and excellent biocompatibility. Herein, several new conjugated polymers with D₂-D₁-A structures were easily prepared through one-pot coupling using triphenylamine as well as thiophenes as electron donors and benzothiadiazole as electron acceptors. Interesting, their optical performance and power conversion efficiency could be tuned by side chains on thiophenes (D₁). The introduction of ethane-1,2-diylbis(oxy) into D₁ as side chain significantly improves fluorescence imaging brightness, photothermal conversion efficiency and hydrophilicity, and extends emission wavelength, which are beneficial for phototheranostic. The side chain modification provides new opportunity to design efficient phototheranostics without construction new fluorescent skeletons.