Synthesis and Characterization of Halogen-Free Flame Retardant Two-Component Waterborne Polyurethane by Different Modification

Diethyl <i>N</i>,<i>N</i>-bis­(2-hydroxyethyl)­aminomethyl­phosphonate and halogen-free poly­(phosphate) as reactive halogen-free flame retardants and soft or hard segment modifiers were compounded to waterborne polyurethane polyols after being emulsified and then were mixed with isophorone diisocyanate and dimethylol­propionic acid to synthesize two-component waterborne polyurethanes having fire resistance. As a result, the rheological behavior of prepolymer emulsion really accords with characteristics of non-Newtonian fluid. The highest limit oxygen index is 27.8% in two-component system modified by hard segment, which was 527.5% than the clean; meanwhile, one is 28.6% in another two-component system, which was 627.6% than the clean. The hardness, solvent resistance, and mechanical property in both of the two-component systems are outstanding. Adding flame retardant can effectively improve the flame resistance, tensile strength, and pot-life of two-component waterborne polyurethanes, especially in being modified by soft segment

Toward Alleviating Voltage Decay by Sodium Substitution in Lithium-Rich Manganese-Based Oxide Cathodes

Lithium-rich manganese-based oxides (LMROs), as one of the most promising high-capacity cathodes, suffer from serious capacity fading and discharge voltage decay during repeated cycles. Here we have successfully enhanced cycle stability and rate capability of LMRO cathode material through introducing a certain amount of Na into LMRO microspheres. In particular, the discharge voltage decay per cycle significantly decreases from 4.40 to 1.60 mV. These enhancements may be attributed to the Na in Li layers, which can promote the kinetics of lithium ion diffusion and facilitate the electronic and ionic conductivity. More remarkably, Na dopant can effectively suppress the transformation from layered to spinel structure by serving as the fixed pillars in Li layers to inhibit the formation of three adjacent vacancies and Mn migration. In addition, full-cell investigations further show the Na-doped LMRO materials have great commercial value. Therefore, our findings may boost understanding in designing high-capacity and good stability cathode materials for LIBs

A crystalline bisindolylmaleimide with strong solid-state fluorescence of red color and its analogous cross-linked polymer without fluorescence

<p>A crystalline bisindolylmaleimide (BIM) <b>3</b> with strong fluorescence in the solid state was prepared and studied. Its analogous cross-linked polymer <b>4</b> with the same BIMs fluorophore was designed and characterized. The investigation of the covalent bonding networking effect on the solid-state fluorescence was carried out by the comparison between <b>3</b> and <b>4</b>.</p

Organoboron-Based Photochromic Copolymers for Erasable Writing and Patterning

We report herein the first examples of organoboron-based photochromic polymers. The synthesis of a series of blue fluorescent random copolymers bearing photochromic boron repeating units, poly­[(6-B­(ppy)­Mes₂)­oxyhexyl methacrylate)_<i>m</i>-<i>r</i>-(<i>tert</i>-butyl methacrylate)_<i>n</i>], ppy = 2-phenylpyridyl and Mes = mesityl, via atom transfer free radical polymerization (ATRP) has been accomplished. These new polymers display thermally reversible photochromism, switching color from colorless to deep blue, and fluorescence from bright sky blue to deep blue. By controlling the monomer ratio, the photoisomerization quantum efficiencies of the polymers can be tuned effectively. In addition, the number of boron units in the polymer has been found to have a significant impact on fluorescence quenching efficiency. The new organoboron-based polymers can be used effectively as a switchable/erasable ink on glass or paper substrate or for creating switchable/erasable patterns as neat polymer films

Occupancy Model for Predicting the Crystal Morphologies Influenced by Solvents and Temperature, and Its Application to Nitroamine Explosives

A new occupancy model for predicting the crystal morphologies influenced by solvent and temperature is proposed. In the model, the attachment energy is corrected by a relative occupancy, which is the occupancy of a solute molecule relative to the total ones of a solute molecule and a solvent molecule. The occupancy is defined proportional to the averaged interaction energy between a solute or solvent molecule and a crystal surface. The validity of the model is confirmed by its successful applications to predict the crystal morphologies of a class of well-known nitroamino explosives hexahydro-1,3,5-trinitro-1,3,5- triazine, octahydro-1,3,5,7-tertranitro-1,3,5,7-tetrazocine and 2,4,6,8,10,12-hexanitrohexaaz-aisowurtzitane grown in solution. Furthermore, the applications of this model regarding concentration, molecular diffusion ability in solution, and mixed solvents are prospected