Helical Folding of π-Conjugated Polymers Bearing Glucose-Linked Biphenyl Units in the Main Chain: Application to Circularly Polarized Luminescence Materials

Abstract

Abstract We have synthesized a series of chiral π-conjugated polymers bearing glucose-linked biphenyl units in the main chain through copolymerizations of a key diethynyl compound (GLB-1), containing the structural element of naturally-occurring ellagitannin, with various diiodoaryls. The circular dichroism and circularly polarized luminescence properties of the obtained polymers were investigated in solution and the solid state. Based on a comparative study using the corresponding unimer model compounds, poly-3 and poly-4 bearing (oligo)thiophene-type comonomer units are considered to be able to fold into an excess one-handed helical conformation in solution and the solid state under an appropriate exterior environment. In contrast, analogous polymers bearing p- and m-phenylene residues as comonomer units did not form regular higher-ordered structures. We also observed that poly-3 and poly-4 efficiently emitted left-handed circularly polarized light with a corresponding fluorescence region arising from their helical chirality, and possessed dissymmetry factors of approximately 1.0 × 10−2 for the film state.