A sulfur electrode exhibiting strong polysulfide chemisorption using a porous N, S dual-doped carbon is reported. The synergistic functionalization from the N and S heteroatoms dramatically modifies the electron density distribution and leads to much stronger polysulfide binding. X-ray photoelectron spectroscopy studies combined with ab initio calculations reveal strong Li(+) -N and Sn (2-) -S interactions. The sulfur electrodes exhibit an ultralow capacity fading of 0.052% per cycle over 1100 cycles.
Nanocrystalline cellulose (NCC) is an emerging renewable nanomaterial that holds promise in many different applications, such as in personal care, chemicals, foods, pharmaceuticals, etc. By appropriate modification of NCC, various functional nanomaterials with outstanding properties, or significantly improved physical, chemical, biological, as well as electronic properties can be developed. The nanoparticles are stabilised in aqueous suspension by negative charges on the surface, which are produced during the acid hydrolysis process. NCC suspensions can form a chiral nematic ordered phase beyond a critical concentration, i.e. NCC suspensions transform from an isotropic to an anisotropic chiral nematic liquid crystalline phase. Due to its nanoscale dimension and intrinsic physicochemical properties, NCC is a promising renewable biomaterial that can be used as a reinforcing component in high performance nanocomposites. Many new nanocomposite materials with attractive properties were obtained by the physical incorporation of NCC into a natural or synthetic polymeric matrix. Simple chemical modification on NCC surface can improve its dispersability in different solvents and expand its utilisation in nano-related applications, such as drug delivery, protein immobilisation, and inorganic reaction template. This review paper provides an overview on this emerging nanomaterial, focusing on the surface modification, properties and applications of NCC.
pH-Responsive polymers are systems whose solubility, volume, and chain conformation can be manipulated by changes in pH, co-solvent, and electrolytes. This review summarizes recent developments covering synthesis, physicochemical properties, and applications in various disciplines. A variety of synthetic methodologies comprising of emulsion polymerization and living radical polymerization techniques are described, and some of their salient features are highlighted. Several polymeric systems, such as homopolymers, block copolymers, microgels, hydrogels and polymer brushes at interfaces are reviewed, where important characteristics that govern their behavior in solutions are described. Potential applications of these systems in controlled drug delivery, personal and home care, industrial coatings, biological and membrane science, viscosity modifiers, colloid stabilization, and water remediation, are discussed.
Pickering emulsions possess many advantages over traditional surfactant stabilized emulsions. For example, Pickering emulsions impart better stability against coalescence and, in many cases, are biologically compatible and environmentally friendly. These characteristics open the door for their use in a variety of industries spanning petroleum, food, biomedicine, pharmaceuticals, and cosmetics. Depending on the application, rapid, but controlled stabilization and destabilization of an emulsion may be necessary. As a result, Pickering emulsions with stimuli-responsive properties have, in recent years, received a considerable amounts of attention. This paper provides a concise and comprehensive review of Pickering emulsion systems that possess the ability to respond to an array of external triggers, including pH, temperature, CO2 concentration, light intensity, ionic strength, and magnetic field. Potential applications for which stimuli-responsive Pickering emulsion systems would be of particular value, such as emulsion polymerization, enhanced oil recovery, catalyst recovery, and cosmetics, are discussed.
This paper describes the rheological behavior of a HEUR (hydrophobic ethoxylated urethane) associative polymer with C16H33 end groups at 2.0 wt % concentration in aqueous solution. Under normal steady shear, this solution exhibits Newtonian behavior at low shear rates and, as the shear rate is increased, passes through a shear-thickening region before exhibiting a sharp decrease in viscosity. Here we report superposition-of-oscillation experiments on steady-shear flows to examine the state of the network structure under different shear conditions. The technique involves applying a steady shear deformation to the fluid, and once the steady state is achieved, a small amplitude oscillation is imposed on the sample to measure the linear viscoelastic properties. We observe that within the shear-thickening region, the plateau modulus is larger than in the Newtonian region, suggesting that shear-thickening is the result of a shear-induced increase in the density of mechanically active chains, which may be due to incorporation of free micelles or higher aggregates into the network structure. In the shear-thinning region, the Maxwell relaxation time decreases with increasing shear stress or shear rate. Thus shear thinning is a consequence of a shear-enhanced exit rate of the hydrophobic end groups from the micellar junctions of the network. This is the first experimental evidence for shear enhancement of the relaxation rate of an associative polymer network.
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