Shrinkability of ethylene vinyl acetate/polyurethane blends and their characterization

Heat shrinkability of the polymer, which depends on the elastic memory, is being utilized in various applications, mainly in the field of encapsulation. The elastic memory is introduced into the system in the form of an elastomeric phase. Here the blends of ethylene vinyl acetate and polyurethane were studied with reference to their shrinkability, introducing crosslinking in both the phases. It is found that with increase in elastomer content the shrinkage increased to a certain level and then decreased. With increase in cure time shrinkage is decreased. It is seen that high‐temperature (HT) stretched samples showed higher shrinkage than room temperature (RT) stretched one. Generally, the crystallinity of the HT stretched sample is higher than that of low‐temperature stretched sample, which is again higher than that of original sample. From high temperature differential scanning calorimetry it is found that with increase in PU content stability towards oxygen is increased and further high temperature processing decreases the initial degradation temperature but enhances the rate of degradation. From scanning electron microscopy it is seen that an HT stretched sample is more elongated than an RT stretched one. Copyright © 2000 John Wiley & Sons, Ltd.     

Palladium(II) Complexes of 1-Phosphaisoprene Molecules and Polymers: Reversible Cross-Linking of a Phosphorus-Containing Polymer

The anionic polymerization of 1-phosphaisoprene [Mes*P=C(Me)−CH=CH₂ (E- 1 )] affords poly(1-phosphaisoprene) 2 in high yield (75 %). Concentrated solutions of polymer 2 (M_n=21,800 g mol⁻¹; Đ=1.02) a P-analogue of natural rubber, undergo gelation upon treatment with [Pd(cod)Cl₂] (0.15 P equiv). Evidence for P-coordination of 2 to Pd^II was obtained by ³¹P and ¹H NMR spectroscopy. The gelation is reversed by the addition of PMe₃ and the reformation of recoverable 2 along with [Pd^II−PMe₃] complexes were confirmed by ³¹P NMR spectroscopy. The use of labile metal-ligand bonds to reversibly form gels is unprecedented and has relevance to self-healing materials. In contrast, coordination of 2 to [Pd(η³-C₃H₅)(μ-Cl)]₂ affords the well-defined complex 2 ⋅ [Pd(η³-C₃H₅)Cl] which was characterized by ³¹P, ¹H, ¹³C{¹H} NMR spectroscopy and GPC. This polymer chemistry was complemented by detailed molecular model studies of the coordination chemistry of monomer 1-phosphaisoprene E- 1 with [Pd(cod)Cl₂] and [Pd(η³-C₃H₅)(μ-Cl)]₂].     

Acetylene-Mediated Borophosphene Dirac Materials as Efficient Anode Materials for Lithium-Ion Batteries

Generally, graphynes have been generated by the insertion of acetylenic content (−C≡C−) in the graphene network in different ratios. Also, several aesthetically pleasing architectures of two-dimensional (2D) flatlands have been reported with the incorporation of acetylenic linkers between the heteroatomic constituents. Prompted by the experimental realization of boron phosphide, which has provided new insights on the boron-pnictogen family, we have modelled novel forms of acetylene-mediated borophosphene nanosheets by joining the orthorhombic borophosphene stripes with different widths and with different atomic constituents using acetylenic linkers. Structural stabilities and properties of these novel forms have been assessed using first-principles calculations. Investigation of electronic band structure elucidates that all the novel forms show the linear band crossing closer to the Fermi level at Dirac point with distorted Dirac cones. The linearity in the hole and electronic bands impose the high Fermi velocity to the charge carriers close to that of graphene. Finally, we have also unravelled the propitious features of acetylene-mediated borophosphene nanosheets as anodes in Li-ion batteries.     

Exploring Nucleobase Modifications in Oligonucleotide Analogues for Use as Environmentally Responsive Fluorophores and Beyond

Over the past two decades, it has become abundantly clear that nucleic acid biochemistry, especially with respect to RNA, is more convoluted and complex than previously appreciated. Indeed, the application and exploitation of nucleic acids beyond their predestined role as the medium for storage and transmission of genetic information to the treatment and study of diseases has been achieved. In other areas of endeavor, utilization of nucleic acids as a probe molecule requires that they possess a reporter group. The reporter group of choice is often a luminophore because fluorescence spectroscopy has emerged as an indispensable tool to probe the structural and functional properties of modified nucleic acids. The scope of this review spans research done in the Hudson lab at The University of Western Ontario and is focused on modified pyrimidine nucleobases and their applications as environmentally sensitive fluorophores, base discriminating fluorophores, and in service of antisense applications as well as tantalizing new results as G-quadruplex destabilizing agents. While this review is a focused personal account, particularly influential work of colleagues in the chemistry community will be highlighted. The intention is not to make a comprehensive review, citations to the existing excellent reviews are given, any omission of the wonderful and impactful work being done by others globally is not intentional. Thus, this review will briefly introduce the context of our work, summarize what has been accomplished and finish with the prospects of future developments.     

Engineering Soluble Diketopyrrolopyrrole Chromophore Stacks from a Series of Pd(II)-Based Ravels**

A strategy to engineer the stacking of diketopyrrolopyrrole (DPP) dyes based on non-statistical metallosupramolecular self-assembly is introduced. For this, the DPP backbone is equipped with nitrogen-based donors that allow for different discrete assemblies to be formed upon the addition of Pd(II), distinguished by the number of π-stacked chromophores. A Pd₃L₆ three-ring, a heteroleptic Pd₂L₂L′₂ ravel composed of two crossing DPPs (flanked by two carbazoles), and two unprecedented self-penetrated motifs (a Pd₂L₃ triple and a Pd₂L₄ quadruple stack), were obtained and systematically investigated. With increasing counts of stacked chromophores, UV/Vis absorptions red-shift and emission intensities decrease, except for compound Pd₂L₂L′₂, which stands out with an exceptional photoluminescence quantum yield of 51 %. This is extraordinary for open-shell metal containing assemblies and explainable by an intra-assembly FRET process. The modular design and synthesis of soluble multi-chromophore building blocks offers the potential for the preparation of nanodevices and materials with applications in sensing, photo-redox catalysis and optics.     

Organic Supercapacitors as the Next Generation Energy Storage Device: Emergence,Opportunity, and Challenges

Harnessing new materials for developing high-energy storage devices set off research in the field of organic supercapacitors. Various attractive properties like high energy density, lower device weight, excellent cycling stability, and impressive pseudocapacitive nature make organic supercapacitors suitable candidates for high-end storage device applications. This review highlights the overall progress and future of organic supercapacitors. Sustainable energy production and storage depend on low cost, large supercapacitor packs with high energy density. Organic supercapacitors with high pseudocapacitance, lightweight form factor, and higher device potential are alternatives to other energy storage devices. There are many recent ongoing research works that focus on organic electrolytes along with the material aspect of organic supercapacitors. This review summarizes the current research status and the chemistry behind the storage mechanism in organic supercapacitors to overcome the challenges and achieve superior performance for future opportunities.     

Mapping the Methanol-to-Gasoline Process Over Zeolite Beta

Decarbonizing the transportation sector is among the biggest challenges in the fight against climate change. CO₂-neutral fuels, such as those obtained from renewable methanol, have the potential to account for a large share of the solution, since these could be directly compatible with existing power trains. Although discovered in 1977, the zeolite-catalyzed methanol-to-gasoline (MTG) process has hardly reached industrial maturity, among other reasons, because maximizing the production of gasoline range hydrocarbons from methanol has proved complicated. In this work, we apply multimodal operando UV/Vis diffuse reflectance spectroscopy coupled with an online mass spectrometer and “mobility-dependent” solid-state NMR spectroscopy to better understand the reaction mechanism over zeolites H-Beta and Zn-Beta. Significantly, the influential co-catalytic role of oxymethylene species is linked to gasoline formation, which impacts the MTG process more than carbonylated species.     

The evolution of structure–property relationship of P2-type Na0.67Ni0.33Mn0.67O2 by vanadium substitution and organic electrolyte combinations for sodium-ion batteries

Journal of Solid State Electrochemistry - Solid-state synthesis of novel electrode materials of P2-type layered oxides Na0.67Ni0.33-xVxMn0.67O2 (where x = 0, 0.05, and 0.11) for the...