Room Temperature Synthesis of a Well-Defined Conjugated Polymer Using Direct Arylation Polymerization (DArP).

While a major improvement to the sustainability of conjugated polymer synthesis, traditional direct arylation polymerization (DArP) still requires high temperatures (typically >100 °C), necessitating a significant energy input requirement. Performing DArP at reduced or ambient temperatures would represent an improvement to the sustainability of the reaction. Here we describe the first report of a well-defined conjugated polymer synthesized by DArP at room temperature. Previous efforts toward room temperature DArP relied on the use of a near-stoichiometric silver reagent, an expensive coinage metal, which makes the reaction less cost-effective and sustainable. Here, room temperature polymerizations of 3,4-ethylenedioxythiophene (EDOT) and 9,9-dioctyl-2,7-diiodofluorene were optimized and provided molar mass (Mn) up to 11 kg/mol PEDOTF, and performing the reaction at the standard ambient temperature of 25 °C provided Mn up to 15 kg/mol. Model studies using other C-H monomers of varying electron density copolymerized with 9,9-dioctyl-2,7-diiodofluorene provided insight into the scope of the room temperature polymerization, suggesting that performing room temperature DArP is highly dependent on the electron richness of the C-H monomer.

Synthesis of Block Copolymers Containing Stereoregular Pendant Electroactive Blocks.

The stereoregular nonconjugated pendant electroactive polymer (NCPEP) poly((N-carbazolylethylthio) propyl methacrylate) (PCzETPMA) has recently shown charge carrier mobilities that are on par with conjugated polymers. Here, we increased the complexity of the architecture for this NCPEP by introducing a polystyrene (PS) block via an anionic, living polymerization yielding a family of PS-b-PCzETPMA block copolymers as the first examples of NCPEP-block-copolymers with controlled stereoregularity of the NCPEP-blocks. Through this methodology we were able to control the molar masses, PS to PCzETPMA block ratios, and tacticities of the PCzETPMA-blocks. We found all three parameters to significantly impact the hole mobilities (µh) of the resulting copolymers, which increased with higher molar masses, longer PCzETPMA-blocks, and higher isotacticity of the PCzETPMA-block, giving the best µh of 2.33 × 10-5 cm2/V·s after annealing at 150 °C for the highest molar mass copolymer with a dominant isotactic PCzETPMA-block. This work is the first reported synthesis of a block copolymer bearing a NCPEP-block with a controlled tacticity and demonstrates that such complex polymer architectures can be realized with NCPEPs while maintaining control over their stereoregularity and without significantly suppressing the hole mobility in the resulting copolymers.