Efficient Tin-Free Route to a Donor–Acceptor Semiconducting Copolymer with Variable Molecular Weights

Abstract

For the fabrication of efficient photovoltaic devices and thin-film transistors, π-conjugated polymers with high molecular weight are desirable as they frequently show superior charge transport, morphological, and film-forming properties. Herein, we present an extremely fast tin-free method to polymerize a naphthalene diimide-dithiophenebased anion-radical monomer in the presence of Pd catalyst having bulky and electron-rich tritert-butylphosphine ligands (Pd/P t Bu 3 ). With this method, the corresponding semiconducting polymer, PNDIT2 (also known as P(NDI2OD-T2 or N2200) with a molecular weight in excess of 1000 kg/mol can be obtained quickly at room temperature and at rather low catalyst concentrations. In general, molecular weights of resulting polymer can be regulated by reaction conditions (e.g., catalyst concentration and reaction time). Besides high molecular weight PNDIT2 (e.g., with M N ∼ 350 kg/mol, Đ M =2.9), PNDIT2 with moderate molecular weight (e.g., M N ∼ 110 kg/mol, Đ M = 2.3) and low molecular weight (e.g., M W ∼ 12 kg/mol, Đ M = 1.9), can also be obtained. It was found that thus-prepared PNDIT2 exhibits field-effect electron mobilities of up to ∼0.31 cm 2 /(V s), similar to the Stille-derived N2200 control polymer (up to ∼0.33 cm 2 /(V s)). Preliminary studies demonstrated that Pd/P t Bu 3 catalyst is remarkably efficient in polymerizing of other anion-radical monomers, such as isoindigo-, and diketopyrrolopyrrole-based ones, although conventional Ni and Pd catalysts (e.g., Ni(dppp)Cl 2 , Ni(dppp)Cl 2 , Pd(PPh 3 ) 4 ) failed to polymerize these monomers.

Highly Planarized Naphthalene Diimide–Bifuran Copolymers with Unexpected Charge Transport Performance

“…Most likely, subsequent coupling of prepolymerized Br(Fu-NDI-Fu)nBr segments may have led to high molecular weight and precipitation, whereby the yield of soluble product can be maximized by reducing the reaction time, thus limiting precipitation. 40 To enable high yields and overcome issues with precipitation, target molecular weights for this comparative study were set to M n,SEC ≈ 17 kg/mol. Thus, a set of three samples, referred to as PNDIFu2-C16, PNDIFu2-C20, PNDIT2-C16, with M n,SEC ≈ 16, 17, 18, kDa, respectively, and dispersities around 2.4 were prepared using NidpppCl 2 .…”

Nonstoichiometric Stille Coupling Polycondensation via an Intramolecular Pd(0) Catalyst Transfer Using Excess Phthalimide Monomer

“…In this system, the Pd(0) catalyst transfers within the single molecule after the first reaction, forming a Pd(0)‐olefin complex, which selectively activates the other reactive site. Such Pd(0) catalyst‐transfer systems have also been well established for the precise synthesis of π‐conjugated polymers with predictable number‐average molecular weights ( M n values) and low dispersities ( Đ M values) . Previously, our group reported a nonstoichiometric polycondensation based on a Stille coupling reaction that afforded high‐molecular‐weight naphthalene‐diimide (NDI)‐based π‐conjugated polymers probably derived from the intramolecular Pd(0) catalyst transfer via a Pd(0)‐π complex .…”

Influence of Semiconductor Thickness and Molecular Weight on the Charge Transport of a Naphthalenediimide-Based Copolymer in Thin-Film Transistors

“…Two samples, indicated as P-23 with a MW ≈ 23 kg/mol and a polydispersity index (PDI) = 1.9 and P-250 with a MW ≈ 250 kg/mol and a PDI = 2.3, were synthesized by recently developed chain-growth polycondensation 38−57 catalyzed by a palladium complex ligated by bulky and electron-rich tri-tert-butylphosphine. 58 The commercially available P(NDI2OD-T2) with an intermediate molecular weight (MW = 72 kg/mol, PDI = 3.2), prepared by step-growth Stille polycondensation and designated here as P-72, was also investigated for comparison. The device performances were correlated to film morphologies studied by atomic force microscopy (AFM) and X-ray diffraction methods.…”