Naphthalene diimide (NDI) copolymers are attractive n-type materials for use in organic electronic devices. Four highly soluble NDI polymers are presentedeach differing only in the thiophene content comprising the material. Electron mobilities as high as 0.076 cm2 V−1 s−1 for the novel material PNDI-3Th are reported. Polymer crystallinity and general macromolecular order are shown to effectively improve by increasing the number of thiophene units within the polymer backbone. The structure−property relationship of NDI−thiophene copolymers is presented and discussed as it pertains to organic field effect transistor (OFET) performance.

Solution-processable n-type ladder-based polymers are highly desirable due to their potential capability to form strong π–π interactions. A series of 5 highly soluble naphthalene diimide (NDI) polymers are presented, differing in the degree to which they are able to form imine-bridged ladder polymer structures. Average electron mobilities as high as 0.0026 cm2 V–1 s–1, which show an electron-mobility improvement of 4 orders of magnitude following ladderization, and on/off current ratios on the order of 104 are reported for the novel material PNDI-2BocL, an alkyl-substituted poly(benzoquinolinophenanthrolinedione). The structure–property relationship of the aforementioned series of copolymers is presented and discussed as it pertains to organic field-effect transistor (OFET) performance.

In this study, we demonstrate in‐situ n‐doping and crosslinking of semiconducting polymers as efficient electron‐transporting materials for inverted configuration polymer solar cells. The semiconducting polymers were crosslinked with bis(perfluorophenyl) azide (bis‐PFPA) to form a robust solvent‐resistant film, thereby preventing solvent‐induced erosion during subsequent solution‐based device processing. In addition, chemical n‐doping of semiconducting polymers with (4‐(1,3‐dimethyl‐2,3‐dihydro‐1H‐benzoimidazol‐2‐yl)phenyl)dimethylamine (N‐DMBI) substantially improved the power conversion efficiency of solar cells from 0.69% to 3.42%. These results open the way for progress on generally applicable polymeric interface materials, providing not only high device performance but also an effective fabrication method for solution‐processed multilayer solar cell devices.

Naphthalene diimide copolymers are attractive ntype materials due to their high electron affinities, high electron mobilities, and exceptional stability. Herein, we report a series of NDI-fused-thiophene based copolymers with each copolymer differing in the number of fused thiophenes in the donor monomer. Increasing the number of fused-thiophene moieties within an NDI-copolymer backbone is shown to not only enable tuning of the electronic structure but also improve charge mobilities within the active layer of organic field-effect transistors. Electron mobilities and on/off ratios as high as 0.012 cm 2 V 21 s -1 and I on / I off > 10 5 were measured from n-channel thin-film transistors fabricated using NDI-xfTh copolymers. Bulk heterojunction solar cell devices were also fabricated from the NDI-xfTh copolymer series in blends with poly(3-hexylthiophene) (P3HT) with PNDI-4fTh-based devices yielding the largest J sc (0.57 mA cm 22 ) and fill factor (55%) in addition to the highest measured PCE for this series (0.13%).

Silicone elastomers have broad versatility within a variety of potential advanced materials applications, such as soft robotics, biomedical devices, and metamaterials. A series of custom 3D printable silicone inks with tunable stiffness is developed, formulated, and characterized. The silicone inks exhibit excellent rheological behavior for 3D printing, as observed from the printing of porous structures with controlled architectures. Herein, the capability to tune the stiffness of printable silicone materials via careful control over the chemistry, network formation, and crosslink density of the ink formulations in order to overcome the challenging interplay between ink development, post-processing, material properties, and performance is demonstrated.

A series of donor−acceptor copolymers based on a new silafluorene containing multifused heptacylic arenes have been designed and synthesized in order to further modulate and optimize their electronic and optical properties. Polymer solar cells based on a blend of these polymers and PC 61 BM exhibited high open circuit voltages of up to 0.86 V. Through simple and straightforward engineering of molecular structures, the devices based on the PSiFDCTBT:PC 61 BM (1:3.5 in wt %) blend provided, on average, a V oc of 0.86 V, a J sc of 8.8 mA/cm 2 , a FF of 56%, delivering a PCE of 4.2%.

shown that architecture could be used to manipulate the reactivity of aluminum/ copper oxide (Al/CuO) thermites by tailoring the flow of gases and entrained particles using structure. [23] A similar behavior had previously been seen in porous-Sibased energetic materials. [21] This is an exciting result in that it enables one to tailor the energy release rate in such materials without defaulting to the conventional approach of changing the formulation.To further expand upon the previous results, we seek to develop AM formulations which can enable a wide range of architectures to be printed. With this, we can design test articles to further understand and quantify to what extent architecture can be used to control reactivity. However, the direct printing of thermite raises safety concerns since, as-mixed, the materials can lead to a rapid reaction in the event of accidental ignition. A far safer approach would be to formulate the precursor materials separately, and then to directly mix during the printing process.In this work, we formulated an Al and a CuO precursor ink separately. One factor in the choice of these precursors was to pick two systems that could be formulated with similar rheological properties, as disparate rheological properties could lead to potential issues during mixing operations. Al and CuO powder feedstock materials were formulated using micron-sized particles of the materials incorporated into an aqueous hydrogel matrix to render an extrudable prethermite "ink." The rheology of these high solids loaded prethermite inks had to be such that the inks could be extruded through a nozzle (i.e., shear thinning) as wet filaments. The formulation parameters can be seen in Table 1, and some considerations are discussed later in the text. Once formulated, the inks were loaded into a syringe and mounted on the printer. A schematic of the printing setup is shown in Figure 1. The basic components of this setup are highlighted, and include two mounts for syringes, linear extrusion motors, and a precise xyz positioning stage (Aerotech). After extrusion, parts are dried in air and the as-deposited printed filaments retain the properties possessed by the dry powder feedstock material. The formulation and printability of the individual materials are investigated; we subsequently show that the two materials can be mixed on-the-fly to render an ignitable thermite ink.Additive manufacturing (AM) has recently shown great promise as a means to tailor a wide range of material properties, both quasi-static and dynamic. An example of controlling the dynamic behavior is to tailor the chemical energy release rate in composite energetic materials such as thermiteswhich are a subset of pyrotechnics that use a metal fuel and a metal oxide as an oxidizer. Since these materials are most hazardous once finely mixed, the approach taken here is to formulate the fuel and oxidizer separately such that they can be mixed on-the-fly. Herein, the development, formulation, and characterization of two respective aqueous 3D printable in...