We demonstrate a highly efficient thermal conversion of four differently substituted polydiacetylenes (PDAs 1 and 2a-c) into virtually indistinguishable N = 8 armchair graphene nanoribbons ([8]GNR). PDAs 1 and 2a-c are themselves easily accessed through photochemically initiated topochemical polymerization of diynes 3 and 4a-c in the crystal. The clean, quantitative transformation of PDAs 1 and 2a-c into [8]GNR occurs via a series of Hopf pericyclic reactions, followed by aromatization reactions of the annulated polycyclic aromatic intermediates, as well as homolytic bond fragmentation of the edge functional groups upon heating up to 600 °C under an inert atmosphere. We characterize the different steps of both processes using complementary spectroscopic techniques (CP/MAS C NMR, Raman, FT-IR, and XPS) and high-resolution transmission electron microscopy (HRTEM). This novel approach to GNRs exploits the power of crystal engineering and solid-state reactions by targeting very large organic structures through programmed chemical transformations. It also affords the first reported [8]GNR, which can now be synthesized on a large scale via two operationally simple and discrete solid-state processes.

Rubin and colleagues describe the development of a simple, bottom-up synthetic approach to graphene nanoribbons (GNRs). In contrast to current methods, this process requires only two solid-state transformations. The key to this approach is the in-crystal topochemical polymerization of butadiyne-containing monomers to produce the corresponding polydiacetylene polymers. These polymers are subsequently fully aromatized in the solid state to GNRs at relatively mild temperatures.

Three‐dimensional (3D) printing brings exciting prospects to the realm of conjugated polymers (CPs) and organic electronics through vastly enhanced design flexibility, structural complexity, and environmental sustainability. However, the use of 3D printing for CPs is still in its infancy and remains full of challenges. In this review, we highlight recent studies that demonstrate proof‐of‐concept strategies to mitigate some of these problems. Two general additive manufacturing approaches are featured: direct ink writing and vat photopolymerization. We conclude with an outlook for this thriving field of research and draw attention to the new possibilities that 3D printing can bring to CPs. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1592–1605

Rationally designed, 3D-printed architectures can effectively decouple the mechanical and electrical properties of conducting polymer hydrogels.

Modified polyolefin separators fabricated via a roll-to-roll system exhibit markedly improved compatibility with lithium ion battery electrolytes. Zwitterionic molecules containing a perfluorophenyl azide functional group were synthesized and covalently bound to the surface of commercial polyolefin separators via UV-activated photochemistry. A roll-to-roll prototype system was constructed allowing for the functionalization of large areas of separator under ambient conditions at low cost. Lithium-ion battery cells containing the modified separators exhibit superior electrochemical performance using a common commercial electrolyte. The modified separators, both monolayer PE and trilayer PP/PE/PP, are wetted instantly upon contact with liquid electrolytes lacking linear carbonates. These electrolytes have been designed for use in batteries with advanced thermal stability properties and/or higher voltage windows, which have previously been hindered by incompatibility with commercial trilayer polyolefin separators. This scalable modification technique is able to meet the rapidly growing demand for low-cost, high-performance separators for safer lithium-ion batteries.

Materials are more easily damaged during accidents that involve rapid deformation. Here, a design strategy is described for electronic materials comprised of conducting polymers that defies this orthodox property, making their extensibility and toughness dynamically adaptive to deformation rates. This counterintuitive property is achieved through a morphology of interconnected nanoscopic core–shell micelles, where the chemical interactions are stronger within the shells than the cores. As a result, the interlinked shells retain material integrity under strain, while the rate of dissociation of the cores controls the extent of micelle elongation, which is a process that adapts to deformation rates. A prototype based on polyaniline shows a 7.5‐fold increase in ultimate elongation and a 163‐fold increase in toughness when deformed at increasing rates from 2.5 to 10 000% min−1. This concept can be generalized to other conducting polymers and highly conductive composites to create “self‐protective” soft electronic materials with enhanced durability under dynamic movement or deformation.

Semiconducting polymers are a versatile class of materials that are used in many (opto)­electronic applications, including organic photovoltaics. However, they are inherently disordered and suffer from poor conductivities due to bends and kinks in the polymer chains along the conjugated backbone, as well as disorder at grain boundaries. In an effort to reduce polymer disorder, we developed a method to straighten polymer chains by creating amphiphilic conjugated polyelectrolytes (CPEs) that self-assemble in water into worm-like micelles. The present work refines our design rules for self-assembly of CPEs. We present the synthesis and characterization of a straight, micelle-forming polymer, a derivative of poly­(cyclopentadithiophene-alt-thiophene) (PCT) bearing two ammonium-charged groups per cyclopentadithiophene unit. Solution-phase self-assembly of PCT into micelles is observed by both small-angle X-ray scattering (SAXS) and cryo-electron microscopy (cryo-EM), while detailed SAXS fitting allows for characterization of intra-micellar interactions and inter-micelle aggregation. We find that PCT displays significant chain straightening thanks to the lack of steric hindrance between its alternating cyclopentadithiophene and thiophene subunits, which increases the propensity for the polymer to self-assemble into straight rod-like micelles. This work extends the availability of micelle-forming semiconducting polymers and points to further enhancements that can be made to obtain homogeneous nanostructured polymer assemblies based on cylindrical micelles.

Cutting-edge synthesis is gradually delivering new types of graphene nanoribbons, enabling comparison of their properties to theoretical predictions. In this issue of Chem, Wu and coworkers describe oligomers of N = 5 armchair graphene nanoribbons possessing near-metallic (E g = 0.21 eV) behavior.Graphene nanoribbons (GNRs) are quasi one-dimensional carbon nanostructures that, unlike graphene, exhibit a significant bandgap tailorable through synthesis. GNRs generally have two archetypal edge structures: zigzag or armchair. Zigzag ribbons are predicted to be metallic, whereas armchair ribbons are semiconducting or metallic depending on their width (Figure 1A). Armchair GNRs are divided into three classes according to the number (N) of carbon atoms making up their width. These classes include 3p, 3p + 1, and 3p + 2, where p is an integer, i.e., a GNR with a width of four carbons falls into the class of 3p + 1, where p = 1. Computational analyses have shown that GNRs of classes 3p and 3p + 1 will be semi-conducting with a bandgap inversely proportional to the width, whereas class 3p + 2 should be metallic with a vanishing bandgap. 1