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We have investigated the changes in the molecular conformation, morphology, and conductivity of polyaniline as it transforms from the insulating emeraldine base (PANI-EB) to the conducting emeraldine salt (PANI-ES) in solutions of hexafluoro-2-propanol (HFIP) and in films processed from the same solvent. Since both PANI-EB and PANI-ES dissolve in this single solvent, we are able to observe for the first time conformational changes as a function of the molar doping level, y. HFIP both solvates and complexes PANI-EB (i.e., y = 0) which promotes a disruption in secondary interactions between chains and allows individual polyaniline chains to adopt a more expanded molecular conformation. As PANI-EB is fully doped to PANI-ES (i.e., y = 0.50), a decrease in the GPC retention time and an increase in [η] argues in favor of an expanded chain conformation in HFIP. When the solvent is removed (under very mild conditions) from PANI-ES, the expanded molecular conformation is retained in the solid state, based on the strong absorption of the UV−vis/near-IR free carrier tail at 2500 nm and good room temperature conductivity. The results in this study indicate that the HFIP solvent can be used to process PANI-EB and PANI-ES with diversified dopant counteranions; in some cases, enhanced optical, conductivity, and morphology properties result from the use of this solvent.

The transformation variant of the fcc to fct transformation in FePt thin films was tailored by controlling the stresses in the thin films, thereby allowing selection of in- or out-of-plane c-axis orientation. FePt thin films were deposited at ambient temperature on several substrates with differing coefficients of thermal expansion relative to the FePt, which generated thermal stresses during the ordering heat treatment. X-ray diffraction analysis revealed preferential out-of-plane c-axis orientation for FePt films deposited on substrates with a similar coefficients of thermal expansion, and random orientation for FePt films deposited on substrates with a very low coefficient of thermal expansion, which is consistent with theoretical analysis when considering residual stresses.

The successful synthesis and structural characterization of molecules that represent segments of extended solids is a valuable strategy for learning metric and stereochemical characteristics of those solids. This approach has been useful in cases in which the solids are particularly difficult to crystallize and thus their atomic connectivity and overall structures become difficult to deduce with X-ray diffraction techniques. One such class of materials is the covalently linked C(x)N(y) extended solids, where molecular analogues remain largely absent. In particular, structures of C(3)N(4) solids are controversial. This report illustrates the utility of a simple molecule, N(C(3)N(3))(3)Cl(6), in answering the question of whether triazine based C(3)N(4) phases are layered or instead they adopt 3D structures. Here, we present density functional calculations that clearly demonstrate the lower stability of graphitic C(3)N(4) relative to 3D analogues.

The introduction of energy storage technologies to the grid could enable greater integration of renewables, improve system resilience and reliability, and offer cost effective alternatives to transmission and distribution upgrades. The integration of energy storage systems into the electrical grid can lead to different environmental outcomes based on the grid application, the existing generation mix, and the demand. Given this complexity, a framework is needed to systematically inform design and technology selection about the environmental impacts that emerge when considering energy storage options to improve sustainability performance of the grid. To achieve this, 12 fundamental principles specific to the design and grid application of energy storage systems are developed to inform policy makers, designers, and operators. The principles are grouped into three categories: (1) system integration for grid applications, (2) the maintenance and operation of energy storage, and (3) the design of energy storage systems. We illustrate the application of each principle through examples published in the academic literature, illustrative calculations, and a case study with an off-grid application of vanadium redox flow batteries (VRFBs). In addition, trade-offs that can emerge between principles are highlighted.

An efficient synthesis of (1Z)-1-amino-1,2-dicyano-3-aza-1,3,5-hexatriene (acrodamn), via condensation of acrolein and diaminomaleonitrile (DAMN), is described. A larger laboratory-scale synthesis of 4,5-dicyano-2-vinylimidazole (vinazene) is described in detail. The alkylation of vinazene proceeds with strong electrophiles. The compound, 4,5-dicyano-1-methyl-2-vinylimidazole (1-methylvinazene), undergoes Michael addition with pyrrolidine, morpholine, and thiophenol and at higher temperatures with itself, resulting in step-growth oligomerization. Direct measurements of kinetic rates for vinylic radical addition polymerization of vinazene yielded k app = k p/2√k t f k d values of (7.2 ± 0.25) × 10-3 and (6.6 ± 0.27) × 10-3. Direct measurements of kinetic rates for 1-methylvinazene yielded k app = k p/2√k t f k d values of (4.3 ± 0.31) × 10-3 and (3.7 ± 0.06) × 10-3. Indirect measurements show the polymerization obeys first-order kinetics. The poly(vinazene) is an acidic material with molecular weights ranging from 100 000 to 200 000 and polydispersities between 2.0 and 2.9. The Mark−Houwink constants for poly(vinazene) in 0.05 M LiBr in N-methylpyrrolidinone were K = 3.35 × 10-5 and a = 0.889. The titration behavior is similar to poly(methacrylic acid).