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Diketopyrrolopyrrole (DPP)-based donor–acceptor (D–A) polymers have been extensively employed in a variety of organic electronic devices. However, systematically increasing the quantity of DPP acceptor blocks in the repeating unit and its impact on the performance of organic thin-film transistors (OTFTs) have not been investigated yet. Herein, an acceptor-quantity modulation strategy is put forward to further optimize the optoelectronic properties and the OTFT performance of DPP-based D–A polymers. Thus, three polymers that are composed of 1–3 DPP acceptor blocks are synthesized via C–H direct arylation polymerization (DArP). Notably, these polymers can be obtained within 0.5 h under the optimal DArP conditions and they demonstrate a decent number average molecular weight of 13–25 kg mol−1. Among the three polymers, the dual-acceptor polymer P1DPP-BT exhibits typical ambipolar OTFT performances with electron mobility (μe)/hole mobility (μh) of 0.7/0.45 cm2 V−1 s−1, respectively. Further success in enhancing μe is achieved in the triple-acceptor polymer P2DPP-BT with one more DPP block in the backbone. It shows the best μe up to 1.1 cm2 V−1 s−1. Unexpectedly, incorporating the third DPP block into the repeating unit leads to a dramatic performance decrease (μe/μh ∼ 10−2 cm2 V−1 s−1). Further characterization studies indicate that the lowest unoccupied molecular orbital (LUMO) energy levels decrease monotonically as the acceptor quantity increases. Meanwhile, the polymer packing texture changes from an edge-on orientation to a face-on orientation with a dramatically decreased crystallinity. Thus, the triple-acceptor polymer maintains a balance between the energy levels, crystallinity and packing textures, resulting in the highest electron mobilities among the three polymers. [ABSTRACT FROM AUTHOR]

Sidechain engineering is a powerful molecular design strategy to tune the solid-state packing and structural ordering of conjugated polymers. While the modification of the type and length of sidechains has become a key strategy in tuning the polymer properties, the effects of the sidechain direction on the optoelectronic properties of polymers have been less investigated. Herein, two new isomeric diketopyrrolopyrrole (DPP)-based conjugated polymers (namely P3BT-in and P3BT-out) with different sidechain substitution directions are designed and synthesized based on the O-alkylated DPP isomer (pyrrolo[3,4-c]pyrrol-1(2H)-one). Through comprehensive theoretical studies and experimental characterization, the effects of the sidechain-substitution direction on the optoelectronic properties of polymers and the corresponding performance of organic transistors and near-infrared organic phototransistors (NIR-OPTs) were systematically investigated. Compared to P3BT-out with sidechains spreading in the outer way, P3BT-in with sidechains in the inner way has better molecular planarity, resulting in increased crystallinity. In addition, P3BT-in has deeper LUMO energy levels and a narrower bandgap of 1.06 eV with a stronger light absorption ability, leading to increased electron mobility and n-type NIR photosensitivity. Overall, tuning the sidechain substitution direction could be a useful strategy for the rational design of functional polymers. [ABSTRACT FROM AUTHOR]

π-Conjugated macrocycles have been highly attractive due to their challenging synthesis, fascinating aesthetic structure and unique physical and chemical properties. Although some progress has been made in synthesis, the study of π-macrocycles with different structural characteristics and supramolecular interactions still faces major challenges. In this paper, two new single-bond linked macrocycles (MS-4T/MS-6T) were reported, and the corresponding vinyl-bridged heterocycloarenes (MF-4T/MF-6T) were synthesized by the periphery fusion strategy. Further studies have indicated that the structure of these four macrocycles is determined by both size and curvature, showing unique variations from nearly planar to bowl and then to saddle. Interestingly, the nearly planar MS-4T with a small size and the rigid saddle-shaped MF-6T show no obvious response to fullerenes C 60 or C 70 , while the bowl-shaped MS-6T and MF-4T demonstrate a strong binding affinity towards fullerenes C 60 and C 70 . What's more, two kinds of co-crystals with capsule-like configurations, MS-6T@C 60 and MS-6T@C 70 , have been successfully obtained, among which the former shows a loose columnar arrangement while the latter displays a unique three-dimensional honeycomb arrangement that is extremely rare in supramolecular complexes. This work systematically studies the π-conjugated macrocycles and provides a new idea for the development of novel host-guest systems and further multifunctional applications., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)