Syntheses, properties and applications of fully conjugated ladder polymers are reviewed, together with an outlook to future opportunities and challenges.

CONSPECTUS: Molecular conformation and rigidity are essential factors in determining the properties of individual molecules, the associated supramolecular assemblies, and bulk materials. This correlation is particularly important for π-conjugated molecular and macromolecular systems. Within such an individual molecule, a coplanar conformation facilitates the delocalization of not only molecular orbitals but also charges, excitons, and spins, leading to synergistically ensembled properties of the entire conjugated system. A rigid backbone, meanwhile, imposes a high energy cost to disrupt such a favorable conformation, ensuring the robustness and persistence of coplanarity. From a supramolecular and material point of view, coplanarity and rigidity often promote strong intermolecular electronic coupling and reduce the energy barrier for the intermolecular transport of charges, excitons, and phonons, affording advanced materials properties in bulk. In this context, pursuing a rigid and coplanar molecular conformation often represents one of the primary objectives when designing and synthesizing conjugated molecules for electronic and optical applications. Two general bottom-up strategiescovalent annulation and noncovalent conformational controlare often employed to construct rigid coplanar π systems. These strategies have afforded various classes of such molecules and macromolecules, including so-called conjugated ladder polymers, graphene nanoribbons, polyacenes, and conformationally locked organic semiconductors. While pursuing these targets, however, one often confronts challenges associated with precise synthesis and limited solubility of the rigid coplanar systems, which could further impede their large-scale preparation, characterization, processing, and application. To address these issues, we developed and utilized a number of synthetic methods and molecular engineering approaches to construct and to process rigid coplanar conjugated molecules and macromolecules. Structure− property correlations of this unique class of organic materials were established, providing important chemical principles for molecular design and materials applications. In this Account, we first describe our efforts to synthesize rigid coplanar π systems fused by various types of bonds, including kinetically formed covalent bonds, thermodynamically formed covalent bonds, N→B coordinate bonds, and hydrogen bonds, in order of increasing dynamic character. The subsequent section discusses the characteristic properties of selected examples of these rigid coplanar π systems in comparison with control compounds that are not rigid and coplanar, particularly focusing on the optical, electronic, and electrochemical properties. For systems bridged with noncovalent interactions, active manipulation of the dynamic bonds can tune variable properties at the molecular or collective level. Intermolecular interactions, solid-state packing, and processing of several cases are then discussed to lay the foundation for future materials applications of rigi...

Well-defined, fused-ring aromatic oligomers represent promising candidates for the fundamental understanding and application of advanced carbon-rich materials, though bottom-up synthesis and structure-property correlation of these compounds remain challenging. In this work, an efficient synthetic route was employed to construct extended benzo[k]tetraphene-derived oligomers with up to 13 fused rings. The molecular and electronic structures of these compounds were clearly elucidated. Precise correlation of molecular sizes and crystallization dynamics was established, thus demonstrating the pivotal balance between intermolecular interaction and molecular mobility for optimized processing of highly ordered solids of these extended conjugated molecules.

Organic solvent nanofiltration (OSN) membranes composed of aromatic porous polymer networks are fabricated by in situ cross-linking. They exhibit excellent chemical/structural stability, molecular-sieving selectivity, and high permeability for OSN.

The construction of coplanar conjugated ladder polymers featuring alternating donor–acceptor units has been achieved in high efficiency using ring-closing olefin metathesis.

To improve methane storage capacity of porous organic materials, this work demonstrates that a rigid ladder-type backbone is more entropically favorable for gas adsorption and leads to a high gas uptake per unit surface area. A porous ladder polymer network was designed and synthesized as the model material via cross-coupling polymerization and subsequent ring-closing olefin metathesis, followed by characterization by solid-state nuclear magnetic resonance (NMR) spectroscopy. This material exhibited a remarkable methane uptake per unit surface area, which outperformed those of most reported porous organic materials. Variable-temperature thermodynamic adsorption measurements corroborated the significantly less negative entropy penalty during high-pressure gas adsorption, compared to its non-ladder-type counterpart. This method provides an orthogonal strategy for multiplying volumetric methane uptake capacity of porous materials. The entropic approach also offers the opportunity to increase deliverable gas upon pressure change while mitigating the performance decline in high-temperature applications.

and Engineering Texas A&MUniversity 3003 TAMU, College Station, TX 77843-3003 (USA) Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Imide-functionalized organic monomers and polymers are attractive in organic optoelectronic devices due to the strong electronwithdrawing ability of the carbonyl units. We report the synthesis of diselenophene−pyrrole-2,5-dione and diselenophene−phthalimide based homopolymers P1−P2 and their corresponding copolymers P3−P4. The effect of the chemical structure by having fused and nonfused diselenophene units, in the polymer backbone, on the physicochemical properties and device fabrication was investigated. The resulting homopolymers and copolymers exhibited small optical band gaps combined with the low-lying HOMO energy levels demonstrated their potential as semiconducting materials in organic field effect transistors. The morphological properties of the microstructure and packing characteristics of the polymer films were investigated by twodimensional grazing incidence wide-angle X-ray scattering (2D GIWAXS). The diffraction patterns of the as-cast and thermally annealed polymer films illustrate that by increasing the fused aromatic cycles in the polymer backbone has an effect on the polymer film crystallinity, which was confirmed by computational studies of the dihedral angle and bond lengths of the polymers.