The mild combination of T3P (n-propanephosphonic acid anhydride) and pyridine has been developed for low-epimerization amide bond formation and implemented for the synthesis of a key intermediate to a glucokinase activator. This robust method is general for the coupling of various racemization-prone acid substrates and amines, including relatively non-nucleophilic anilines, and provides amides in high yields with very low epimerization. With easy reaction setup and product isolation, this protocol offers several practical and experimental benefits.

Development of new dielectric materials is of great importance for a wide range of applications for modern electronics and electrical power systems. The state-of-the-art polymer dielectric is a biaxially oriented polypropylene (BOPP) film having a maximal energy density of 5 J/cm(3) and a high breakdown field of 700 MV/m, but with a limited dielectric constant (∼2.2) and a reduced breakdown strength above 85 °C. Great effort has been put into exploring other materials to fulfill the demand of continuous miniaturization and improved functionality. In this work, a series of polyimides were investigated as potential polymer materials for this application. Polyimide with high dielectric constants of up to 7.8 that exhibits low dissipation factors (<1%) and high energy density around 15 J/cm(3), which is 3 times that of BOPP, was prepared. Our syntheses were guided by high-throughput density functional theory calculations for rational design in terms of a high dielectric constant and band gap. Correlations of experimental and theoretical results through judicious variations of polyimide structures allowed for a clear demonstration of the relationship between chemical functionalities and dielectric properties.

Rational strategies combining computational and experimental procedures accelerate the process of designing and predicting properties of new materials for a specific application. Here, a systematic study is presented on polythioureas for high energy density capacitor applications combining a newly developed modelling strategy with synthesis and processing. Synthesis was guided by implementation of a high throughput hierarchical modelling with combinatorial exploration and successive screening, followed by an evolutionary structure search based on density functional theory (DFT). Crystalline structures of polymer films were found to be in agreement with DFT predicted results. Dielectric constants of $4.5 and energy densities of $10 J cm À3 were achieved in accordance with Weibull characteristic breakdown fields of $700 MV m À1 . The variation of polymer backbone using aromatic, aliphatic and oligoether segments allowed for tuning dielectric properties through introduction of additional permanent dipoles, conjugation, and better control of morphology.

Poly(dimethyltin glutarate) is presented as the first organometallic polymer, a high dielectric constant, and low dielectric loss material. Theoretical results correspond well in terms of the dielectric constant. More importantly, the dielectric constant can be tuned depending on the solvent a film of the polymer is cast from. The breakdown strength is increased through blending with a second organometallic polymer.

Large dielectric constant and band gap are essential for insulating materials used in applications such as capacitors, transistors and photovoltaics. Of the most common polymers utilized for these applications, polyvinyldiene fluoride (PVDF) offers a good balance between dielectric constant, >10, and band gap, 6 eV, but suffers from being a ferroelectric material. Herein, we investigate a series of aliphatic organotin polymers, p­[DMT­(CH2) n ], to increase the dipolar and ionic part of the dielectric constant while maintaining a large band gap. We model these polymers by performing first-principles calculations based on density functional theory (DFT), to predict their structures, electronic and total dielectric constants and energy band gaps. The modeling and experimental values show strong correlation, in which the polymers exhibit both high dielectric constant, ≥5.3, and large band gap, ≥4.7 eV with one polymer displaying a dielectric constant of 6.6 and band gap of 6.7 eV. From our work, we can identify the ideal amount of tin loading within a polymer chain to optimize the material for specific applications. We also suggest that the recently developed modeling methods based on DFT are efficient in studying and designing new generations of polymeric dielectric materials.

Most polyolefins that are used for dielectric materials exhibit a low dielectric constant and operating temperatures up to 70 C. Polyimides offer a means to a higher dielectric constant material by the introduction of a polar group in the polymer backbone and are thermally stable at temperatures exceeding 250 C. A common dianhydride, pyromellitic dianhydride (PMDA), is reacted with various short-chain diamines to produce polymers with high imide density. Homopolymers and copolymers synthesized had dielectric constants ranging from 3.96 to 6.57. These materials exhibit a dielectric constant twice that of biaxially oriented polypropylene and therefore a twofold increase in capacitance as well as maintaining low dissipation factors that are acceptable for this application. The experimental dielectric constants of these materials are also compared to density functional theory calculations and exhibit a close relationship.

To facilitate the development of new polymeric materials, we report the development of new heuristic models to predict the dielectric constant, band gap, dielectric loss tangent, and glass transition temperatures for organic polymers. A new set of features called infinite chain descriptors (ICDs) was designed and developed especially to characterize organic polymers, utilizing methods with minimal dependence on predefined fragment libraries. Machine learning models were built for the aforementioned properties incorporating best practices in the field such as objective feature selection, cross‐validation and external test sets. All models produced in this study showed good performance in prediction. A web tool has been developed and has been made available that supports the input of novel structures. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2082–2091.

Samples of lead zirconium titanate, PbZr 1−x Ti x O 3 (PZT), having x = 0, 0.25, 0.48, 0.55, 0.75 and 1, were studied by 17 O, 207 Pb and 47,49 Ti solid-state NMR. All oxygen sites are clearly resolved for the end-member compositions and are assigned on the basis of line intensity and the correlation of the oxygen shift with increasing Zr/Ti-O bond length. The two distinct O sites characteristic of the end member PbTiO 3 (x = 1) behave differently as x is decreased, indicating that Ti-O-Ti chains in the (001) plane are preserved down to x = 0.25. By contrast, the Ti-O-Ti signal in the [001] direction is absent at x 0.75, which demonstrates there is an important anisotropy in the local structure of PZT solid solutions. A sharp line consistent with a new well ordered oxygen environment appears at the morphotropic boundary (MPB) composition, x = 0.48, and is suggested to be a feature of the monoclinic phase. Although a small amount of lead is in a relatively ordered environment, there is considerable Pb disorder throughout the composition range. The 207 Pb shift dispersion implies a Pb-O distance variation of ∼0.02 Å for x = 0.10, and still larger for other compositions. The intrinsic width of the 47,49 Ti lines is found to remain constant for x values between 0 and 0.50, which indicates that the electric field gradient and the octahedral distortion observed in the PbTiO 3 end-member is little changed even in the presence of considerable Zr doping. These observations are discussed in the context of present models for the development of the average and local structures of PZT solid solutions throughout the phase diagram and across the MPB.