Structural defects in semiconducting conjugated polymers are usually suspected to deteriorate their properties and device performance and therefore complicate batch-to-batch reproducibility. This study investigates homocoupling (hc) defects in copolymers made from dithiazolyldiketopyrrolopyrrole (TzDPPTz) and tetrafluorobenzene (F4) by direct arylation polycondensation (DAP). Hc defects are quantified by 1 H NMR spectroscopy with good accuracy, and the effect of several reaction parameters on the TzDPPTz hc content in the resulting copolymers PTzDPPTzF4 is investigated in detail. A range of polymers with hc contents between 0.6 and 12.4% is used for a detailed structure− function relationship study. Experimentally, it is observed that TzDPPTz hc defects cause bathochromically shifted absorption spectra, decrease photoluminescence, and lower the lowest unoccupied molecular orbital (LUMO) energy level. Thin film morphology, nanostructure, and electron mobility probed by field-effect devices is marginally or not affected. The latter result is explained by theoretical calculations that suggest a localization of the highest occupied molecular orbital on the hc defect, but not that of the LUMO, the latter being relevant for electron transport. Thus, under these conditions, the hc content is not limiting device performance, which makes PTzDPPTzF4 a robust electron-transporting copolymer. These results are promising in the context of batch-to-batch reproducibility and further guide efforts toward a more detailed understanding of hc−function relationships.

Devices and applications that exploit nanoparticle (NP) coupling interactions require the controlled arrangement of primary NPs into defined supracolloidal assemblies. Solution self-assembly of polymer-coated NPs is a scalable approach; however, imparting assembly directionality is still challenging. Current strategies for achieving such directionality include surface encoding of distinct NP sites with polymer ligands, which adds significantly to the complexity of the approach. Moreover, at present, a mechanistic understanding of the self-assembly behavior of polymer-coated NPs is limited due to the hurdle of locally resolved, quantitative characterization under the assembly condition. Herein, we reveal that polystyrene-coated gold nanorods can undergo directional tip-to-tip self-assembly, even when they are uniformly coated with a polymer ligand layer. Our results suggest that directionality in the self-assembly arises from the intrinsic surface charge of the nanorods. These findings open up a straightforward and generic way for achieving directional assembly of anisotropic NPs for future materials concepts.

Lyotropic liquid crystalline (LC) phases offer a means of controlling molecular order and orientation in thin films of conjugated polymers. Surface energy, surface-induced ordering, and film thickness are additional factors determining the molecular order in thin films. Through solvent vapor annealing and in situ atomic force microscopy in the swollen state, we show that in ultrathin films of a poly-(dithiazolyldiketopyrrolopyrrole-tetrafluorobenzene) (PTzDPPTzF4) alternating copolymer stacks of monomolecular-thick layers with a 2.1 nm step height form, which resemble a lyotropic smectic LC phase. Within the smectic layers, the polymer backbones are aligned parallel to the film plane, with edge-on oriented diketopyrrolopyrrole (DPP) cores. Thicker films resemble a semicrystalline morphology with lamellae consisting of blocks. Such lamellae are typical for polymers crystallizing via Strobl's block-forming model. Our findings indicate that molecular order, molecular orientation, and the morphology of PTzDPPTzF4 copolymer films are tunable by LC order and by varying the film thickness according to the desired application of the particular organic electronic devices.