Optimizing the self‐assembly of conjugated polymers and small molecules through structurally programmed non‐covalent control

Abstract

Organic conjugated polymers and oligomers are key electronic materials for applications such as transistors, photovoltaics, and light emitting devices due to their potential for solution processability, mechanical flexibility, and precise structure-based tuning compared to inorganic materials. In dilute environments, the optoelectronic properties of conjugated polymers are largely governed by their constitutional structure and, to a lesser degree, their solution-state intramolecular configuration. In the solid state, intramolecular conformation and intermolecular electronic coupling impact these properties substantially, especially in relation to device performance. Therefore, an increasingly important area of research concerning conjugated materials is developing design strategies aimed at optimizing the solid-state packing for electronic applications. Programming solid-state packing arrangements through discrete non-covalent interactions is an emerging strategy within the context of conjugated polymers. This review focuses on the use of the two most prevalent discrete and directional interactions used to dictate the self-assembly of conjugated polymers and oligomers-hydrogen bonds and chalcogen bonds. We also discuss how these design motifs can imbue conjugated materials with appealing physical properties while simultaneously retaining or improving electronic capabilities.

Bridging the Void: Halogen Bonding and Aromatic Interactions to Program Luminescence and Electronic Properties of π-Conjugated Materials in the Solid State

“…These feature comparable strengths to hydrogen bonding but introduce near-linear directionality owing to the geometry of the halogen σ-hole (Figure ). − This combination of strength and directionality renders XB an essential building block in the noncovalent design toolbox for highly ordered CM molecular assemblies required for optoelectronic applications, including phosphorescence, charge transport, and responsive behavior. − XB interactions are employed only rarely in conjugated polymers, which we at least partially ascribe to the role of the polarizable halogens, such as aryl bromides and iodides, as reactants in the cross-coupling reactions that are often used to prepare such polymers . In contrast, XB is a highly reliable and versatile tool for directing structure across an array of small molecule CM systems and length scales.…”

“…Hydrogen bonds are strong and can be employed via a broad range of hydrogen bond donor and acceptor moieties to direct macromolecular structure, whereas chalcogens and other heteroatoms are already incorporated in many CP structures and can be easily leveraged to direct conformation . We have highlighted how these interactions can engineer optoelectronic and mechanical properties in CPs in a recent review …”

Crystal Structures of Lignocellulosic Furfuryl Biobased Polydiacetylenes with Hydrogen-Bond Networks: Influencing the Direction of Solid-State Polymerization through Modification of the Spacer Length

“…The main difference comes from the presence of an inter molecular N–H···O HB network between the PDA chains for FAM-PDA-1CH2 , whereas with FAM-PDA-3CH2 , we find rather intra molecular HBs. Since HBs may have a considerable impact on the final properties of the overall polymeric material − or on individual macromolecules, we were interested in modeling simplified oligodiacetylenes (ODAs) to get information on the cooperative effects of the HBs. Indeed, cooperative HBs play a crucial role in shaping macromolecular conformations and governing macroscopic properties of biomacromolecules and synthetic polymers. , For example, cooperative inter chain HB network links polypeptide chains together to form a two-dimensional (2D) rigid β-sheet motif, − and on the other hand, the cooperative intra molecular HBs may stabilize the helical conformation of a polypeptide chain (such as an α-helix).…”

Thiophene α-Chain-End-Functionalized Oligo(2-methyl-2-oxazoline) as Precursor Amphiphilic Macromonomer for Grafted Conjugated Oligomers/Polymers and as a Multifunctional Material with Relevant Properties for Biomedical Applications

“…From this point of view, the architecture of g-CPs is an alternative “full of options” for many types of applications because it allows control of the processing–structure–properties relationship from the molecular design stage, when self-assembly can be programmed and structurally optimized [ 51 , 52 ].…”