Azido-Functionalized Thiophene as a Versatile Building Block To Cross-Link Low-Bandgap Polymers

Abstract

We unveil a concept for the design of cross-linkable semiconducting polymers that is based on a modular tercopolymerization which stands out by its low synthetic effort, easy accessibility, and its broad range of applications. 3-(6-Azidohexyl)thiophene was used as a comonomer in the synthesis of a variety of low-bandgap copolymers using different polymerization techniques such as Suzuki–Miyaura cross-coupling and Stille cross-coupling. We show that when only a small amount (5–10 mol %) of azide groups is introduced into the polymers, the impact on absorption and electrochemical properties (HOMO/LUMO values) is negligible. The small amount of azide functionality is however enough to obtain polymers that can easily be cross-linked by UV illumination. Thermal stability of the solid state packing and alignment is studied in neat polymer thin films as well as in blends with [6,6]-phenyl-C71-butyric acid methyl ester (PC70BM) as a relevant model blend system. Solvent resistivity of these polymer films is invest...