Synthesis and Properties of Soluble Fused Thiophene Diketopyrrolopyrrole-Based Polymers with Tunable Molecular Weight

It is challenging to realize both a fully conjugated rigid polymer backbone and high molecular weight at the same time. Previously, we reported a DPP-FT4 polymer with molecular weight up to 30 kDa. A new design and synthesis was required to overcome this limitation. Here, we report the successful synthesis of a conjugated semiconducting polymer with tunable molecular weight over a wide range. Through molecular design and synthesis control, our new polymer can be selectively prepared with number-averaged molecular weight (Mn) ranging from approximately 20 to 100 kDa, realizing both high molecular weight and high solubility at the same time. Four polymers within this range were investigated, with particular emphasis on Mn of 50 kDa (P2) and 97 kDa (P4). The relationships between molecular weight and polymer properties, molecular packing, and electrical behavior are explored in detail. All the polymers in this series are fully soluble in nonchlorinated solvents at room temperature, which is promising for lar...