Synthesis, optical properties, and dual‐color halochromic fluorescence of novel π‐conjugated polymers bearing coumarin unit in the main chain

Abstract A series of novel π‐conjugated polymers bearing alternating coumarin and phenylene units in the main chain backbone was synthesized via Sonogashira coupling reaction. The red‐shifts in the absorption maxima of the polymers indicate the expansion of π‐conjugated system in the polymer main chains. These polymers exhibited strong green fluorescence in organic solvents. Clearly perceptible dual‐color halochromic fluorescence was confirmed for the polymers by the significantly reversible changes of emission color from green to blue during alkalization and acidification processes. The lactone ring opening and closing property in the coumarin molecule functioned as a controllable switch, broadening the applications of the coumarin‐based π‐conjugated polymers as acid–base responsive fluorescence materials.