Influence of the introduction of phenylene units into the polymer backbone on bandgap of conjugated poly(heteroarylene methines)

A series of conjugated poly(heteroarylene methines) containing alternating aromatic and quinoid phenylene-thiophene moieties in the main chain have been synthesized. These polymers are soluble in common organic solvents, such as chloroform, THF. The optical and electrochemical properties of the conjugated poly(heteroarylene methines), such as band gap, redox potentials, ionization potential, and electron affinity, were found to be significantly modified by the size of lateral groups on phenylene units and the number of phenylene units on the phenylene-thiophene moieties. With the increase of the size of lateral groups on phenylene units, the polymers show much bigger conjugated length. And the introduction of two phenylene units between two thiophene units lowers much more band gap than that of one phenylene unit.