Hydrogen Bonds Control Single-Chain Conformation, Crystallinity, and Electron Transport in Isoelectronic Diketopyrrolopyrrole Copolymers

Abstract

The combination of computational methods and advanced characterization techniques is used to highlight the role of the intramolecular hydrogen bond in thienyldiketopyrrolopyrrole (ThDPPTh) copolymerized with tetrafluorobenzene (F4) to PThDPPThF4. We investigate how the torsion potentials of ThDPPTh and isoelectronic dithiazolyldiketopyrrolopyrrole (TzDPPTz) are influenced by hydrogen bonding and translate into different conformation, molecular, structural, and opto-electronic characteristics. ThDPPTh exhibits N,S-syn orientation in the most stable conformer locked by an intramolecular hydrogen bond. In TzDPPTz, such a hydrogen bond is not possible, which leads to a “ring flip” and makes the N,S-anti conformer most stable. Copolymers with F4, PThDPPThF4 and PTzDPPTzF4, exhibit straight and curved backbones, respectively, but similar chain rigidity. These conformations are experimentally confirmed by local packing motifs from solid-state NMR spectroscopy. The differences in conformation strongly influence the opto-electronic and structural properties. X-ray scattering and atomic force microscopy reveal lamellar morphologies of both PThDPPThF4 and PTzDPPTzF4, but increased long range order, reduced paracrystallinity, and larger domains of the former. In-depth analysis of solid-state NMR spectra allows for obtaining information on absolute degrees of crystallinity, which are substantially higher for PThDPPThF4. These differences in structural properties cause field-effect electron mobilities of PThDPPThF4 to be larger by a factor of 20.

Chain Stiffness of Donor–Acceptor Conjugated Polymers in Solution

“…The low torsional disorder of PIDTBT has been attributed to nontraditional hydrogen bonding between the peripheral hydrogen of the IDT and the BT sulfonamide nitrogen . Such intramolecular noncovalent “lock” interactions between adjacent units aid in increasing backbone planarity and reducing torsional disorder. ,− …”

Resolving Atomic‐Scale Interactions in Nonfullerene Acceptor Organic Solar Cells with Solid‐State NMR Spectroscopy, Crystallographic Modelling, and Molecular Dynamics Simulations

“…For fluorinated donor and acceptor moieties such as PM6 and Y6, 2D heteronuclear 13 C– 19 F correlation and 19 F– 1 H correlation experiments provide further insights into inter‐ and intra‐molecular backbone–backbone and backbone–sidechain interactions. [ 50,68,69 ] Despite the high sensitivity of 19 F NMR (100% natural abundance) and substantial chemical shift range, such experiments usually require specialized triple‐resonance H–F–X (X = 13 C) NMR probes. In addition, the sensitivity of 2D 13 C– 19 F correlation experiments relies on relatively weak 13 C– 19 F dipolar interactions between flexible sidechains and backbone moieties.…”

Recent progress in lactam‐based polymer semiconductors for organic electronic devices

“…Sommer and co-workers compared the performances of n-type OFET's by synthesizing TDPP (P102) and thiazole-flanked DPP (TzDPPTz)-based (P103) polymers. 44 Unlike P103, P102 exhibits an "N,S-syn" orientation in which N in the DPP and S in the adjacent thiophene units are oriented in the same direction. The direction of orientation can be attributed to the intramolecular hydrogen bonding between the H atom in thiophene and the carbonyl O atom in the DPP unit.…”