Modern Methods for Conjugated Polymers Preparation: A Concept of Transition Metal-Free Synthesis

Abstract

Cross-coupling technology is still the cornerstone of conjugated polymer synthesis. However, most cross-coupling reactions rely on platinum group metals (e. g. rhodium, palladium, iridium and platinum), and the supply of these rare and expensive metal catalysts is at risk, making the use of these reactions unsustainable. In addition, the contamination of conjugated polymers with trace metallic catalysts is another concern, especially for organic electronics where the products are used in devices whose performance can be affected by even ′undetectable’ levels of metal contaminant. In pursuit of more sustainable chemistry in the future, various organic reactions have been utilized for the synthesis of conjugated polymers without the aid of transition-metal catalysts. Presented herein is a comprehensive overview of organic reactions for the synthesis of conjugated polymers that go beyond transition metal-catalysed cross-coupling reactions. We discuss metal-free synthesis strategies and methods in detail and divide them into “condensation” reactions, “click” reactions and other miscellaneous reactions. Reaction mechanisms and key intermediates are also elucidated. The aim is to provide researchers and practitioners with valuable insights that will enable them to innovate and expand the horizons of conjugated polymer synthesis.