Amide-Containing Alkyl Chains in Conjugated Polymers: Effect on Self-Assembly and Electronic Properties

Abstract

A simple and efficient strategy to modulate the self-assembly and solid-state morphology of conjugated polymers has been developed by incorporating various amounts of amide-containing alkyl side chains to high charge carrier mobility conjugated polymers based on diketopyrrolopyrrole (DPP). Synthetically easily accessible and tunable, the incorporation of amide-containing side chains is a direct strategy to promote intermolecular hydrogen bonding between polymer chains and tune the solid-state morphology. Incorporation of 5–30 mol % of amides in the conjugated polymers was performed without a drastic decrease of solubility. The incorporation of hydrogen-bonding moieties allowed for an improvement of the charge carrier mobility in organic field-effect transistors (OFET) devices, which achieved a maximum value of 2.46 cm2/(V s) at 5 mol % of amides. Morphological investigation showed that the intermolecular hydrogen bonds formed between adjacent amide moieties directly affected the lamellar packing of the polymer and aggregation, without affecting the π-conjugation. Therefore, controlled self-assembly of conjugated polymers through hydrogen-bonding side chains is a promising strategy toward more efficient semiconducting polymers for thin film transistors and other organic electronics.

The Effects of Side Chains on the Charge Mobilities and Functionalities of Semiconducting Conjugated Polymers beyond Solubilities

“…Hydrogen bonding (H bonding) has been widely used to tune intermolecular interactions and self‐assembly structures by considering its relative bonding strength and directionality . On the basis of this consideration, as shown in Scheme and Figure , some of us incorporated urea groups in the side chains of DPP‐based polymers P175–P177 .…”

“…These studies again demonstrate that the incorporation of urea moieties in the side chains is a promising strategy to control the nanoscale morphology, solubility, and polarity of conjugated polymers without reducing their semiconducting performances. They also incorporated amide groups in the side chains of conjugated polymers P184–P187 . The results show that the additional interchain interactions due to H bonding among the amide groups can affect the interchain packing, thin film morphology and, thus, the charge transporting performance of conjugated polymers.…”

The Critical Role of Electron‐Donating Thiophene Groups on the Mechanical and Thermal Properties of Donor–Acceptor Semiconducting Polymers

“…All five samples displayed similar nanofibrillar textures. [39,47] The aggregation behavior was investigated by comparing the relative intensity of peak 0-1 and peak 0-0, the result indicated slight difference in the aggregation behavior for the polymer chain, e.g., DPP-T3 showed 11% decrease in short-range aggregation when compared with DPP-T. There is no direct correlation between the mechanical property and surface morphology of conjugated polymers.…”

“…[44] Apart from backbone engineering, functional side chains were also used to improve the mechanical performance. [46,47] Despite the versatility in improving the mechanical performance of D-A polymers, the dynamics of the conjugated polymer backbone, described by the glass transition temperature, upon using isolated or fused thiophene linkers in the polymer backbone is still not well explored. [45] Noncovalent crosslinking like hydrogen bonding was also shown to be useful by introducing self-healable electrical and mechanical properties to the polymer system.…”

Glass Transition Phenomenon for Conjugated Polymers

“…Those potential weak interactions include: π–π interactions, hydrogen bonds, and metal‐ligand coordination bonds. Many weak interaction bonds were successfully designed into conjugated polymers to endow a self‐healing ability into conjugated polymers. Previous works by the Bao group are great examples for demonstrating this capability.…”