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The hollow glass microsphere (HGM) containing polymer materials, which are named as syntactic foams, have been applied as lightweight materials in various fields. In this study, carboxyl group-containing hyperbranched polymer (HBP) was added to a glass fiber (GF)-reinforced syntactic foam (RSF) composite for the simultaneous enhancement of mechanical and rheological properties. HBP was mixed in various concentrations (0.5–2.0 phr) with RSF, which contains 23 wt% of HGM and 5 wt% of GF, and the rheological, thermal, and mechanical properties were characterized systematically. As a result of the lubricating effect of the HBP molecule, which comes from its dendritic architecture, the viscosity, storage modulus, loss modulus, and the shear stress of the composite decreased as the HBP content increased. At the same time, because of the hydrogen bonding among the polymer, filler, and HBP, the compatibility between filler and the polymer matrix was enhanced. As a result, by adding a small amount (0.5–2.0 phr) of HBP to the RSF composite, the tensile strength and flexural modulus were increased by 24.3 and 9.7%, respectively, and the specific gravity of the composite was decreased from 0.948 to 0.917. With these simultaneous effects on the polymer composite, HBP could be potentially utilized further in the field of lightweight materials. [ABSTRACT FROM AUTHOR]

Abstract: A novel macromonomer of vinyl-terminated bifunctional polyurethane was synthesized and applied to the dispersion polymerization of MMA in ethanol. The existence of the vinyl terminal groups and the grafted macromonomer with PMMA was verified using 1H NMR and 13C NMR. The stable and monodisperse PMMA microspheres having a weight-average diameter of 5.09 μm and a good uniformity of 1.01 were obtained with 20 wt% polyurethane macromonomer. The molecular weight increased, but the size of the synthesized PMMA microspheres decreased with the macromonomer concentration since the macromonomer acts as a reactive stabilizer in dispersion polymerization. Furthermore, the molecular weight of the PMMA prepared by the use of the macromonomer was approximately twofold higher than that prepared by a conventional stabilizer, poly(N-vinylpyrrolidone). The higher molecular weight is thought to originate from the grafting and a possibly slight crosslinking of PMMA molecules due to the bifunctional reactive groups at the ends of macromonomer chains. [Copyright &y& Elsevier]

Herein, Ni-doped Mn 2 O 3 microspheres are successfully synthesized via the facile coprecipitation of metal ions and ammonium bicarbonates, followed by a heat treatment process. Ni-doped Mn 2 O 3 exhibits outstanding catalytic performance toward the oxygen reduction reaction (ORR) in alkaline media with a half-wave potential of 0.801 V, limiting current density of 6.02 mA cm−2 at 0.6 V vs. RHE, outstanding long-term durability, and strong tolerance to methanol. Furthermore, a Zn–air primary battery using Ni-doped Mn 2 O 3 as an air cathode shows high open-circuit voltage of 1.52 V and high power density of 88.2 mW cm−2, outperforming the commercial Pt/C cathode. The exceptional performance of the Ni-doped Mn 2 O 3 microspheres is ascribed to the hierarchical structure, optimized particle size, and Ni incorporation into Mn 2 O 3. The proposed synthesis strategy provides a new methodology for the design and fabrication of electrochemically active transition metal-doped materials as efficient electrocatalysts for a variety of energy storage and conversion reactions. [Display omitted] • Ni-doped Mn 2 O 3 are fabricated via a simple co-precipitation and annealing process. • Ni-doped Mn 2 O 3 shows outstanding activity and long-term durability toward ORR. • Zn-air primary battery using Ni-doped Mn 2 O 3 possess excellent performance. [ABSTRACT FROM AUTHOR]

Abstract: Dispersion polymerization of styrene was investigated using PVA as a steric stabilizer in aqueous alcoholic media. In aqueous methanol and alcohol media, colloidally stable monodisperse polystyrene microspheres are synthesized using BPO and AIBN as initiators and various PVA concentrations of 0.5–10wt.% relative to styrene. The effect of PVA on the size variation is found to be similar to that of conventional stabilizer, PVP. The yield of polymerization is significantly influenced by the amount of PVA. When initiator is changed to AIBN, the yield of polymerization is substantially lower than the BPO systems. Both chemical grafting and physical adsorption of PVA endow stability of the polystyrene particles. Such a mechanism was justified from the FT-IR spectrum of polystyrene particles in which characteristic peaks of PVA molecules are witnessed. The molecular weight increases with the PVA content due to the reduced particle size. The glass transition temperatures of the polystyrene particles lie in 98.9–104.4°C regardless of PVA concentrations. Contrary to PMMA dispersion polymerization with a PVA stabilizer, no discernable change in the glass transition temperature is observed. [Copyright &y& Elsevier]

Abstract: The highly monodisperse polystyrene (PS) microspheres were produced by dispersion polymerization using an amphoteric initiator, -azobis [N-(2-carboxyethyl)-2-2-methylpropionamidine] (VA-057). The polymerization characteristics were investigated and compared with conventional initiators, 2,2-azobis(isobutyronitrile) (AIBN) and benzoyl peroxide (BPO). The monodisperse PS microspheres having the coefficient of variation () of diameter all less than 4% are obtained at very low stabilizer, poly(vinyl pyrrolidone) (PVP) concentrations of 1 and 2 wt%. It is found that the size dependence of the VA-057 system, [VA-057]0.267, is less sensitive than a conventional initiator system. When the same amount, 2 wt%, of AIBN, BPO, and VA-057 is used under the identical PVP concentration of 2 wt%, the ''s are 1.95/11.57, 1.47/22.44, and 2.08 μm/2.50%, respectively. The uniformity of particles was characterized employing an optical analyzer, Turbiscan. For the VA-057 system, the back scattering intensity is linearly reduced with time having a constant sedimentation rate of 48.98 μm/min throughout the settling process. The uniformity of PS particles in the VA-057 system stems from (1) the higher rate of polymerization in early stage of polymerization, followed by significantly faster reduction of the rate, and (2) good dispersion stability of primary particles. Therefore, it is found that the use of an amphoteric initiator, VA-057, is promising for producing monodisperse particles in dispersion polymerization. [Copyright &y& Elsevier]

Although phosphosulfide and P-doped sulfide materials have been widely reported as highly efficient electrocatalysts for the oxygen evolution reaction (OER), the practical application of these materials is severely hindered by their complicated fabrication method. This paper reports a facile preparation of 3D hierarchical flower-like P-doped Ni–Fe disulfide microspheres by successive hydrothermal and one-step phosphosulfidation, using P 2 S 5 as a source of phosphorus (P) and sulfur (S). Owing to the synergistic effect of the binary metal system, the introduction of P, and unique 3D porous architecture, the flower-like P-doped Ni–Fe disulfide microspheres deliver outstanding OER performance—an overpotential of 264 mV to achieve a current density of 10 mA cm−2, a significantly low Tafel slope of 48 mV dec−1, and excellent long-term durability over 50 h with negligible degradation in alkaline media. The fabrication method applied in this study can provide a new facile approach to the design and synthesis of P-doped metal sulfide materials for various electrochemical applications. Image 1 • P-doped Ni–Fe disulfide was synthesized using one-step phosphosulfidation. • The synergistic effect of binary metal and P doping led to excellent OER activity. • P-doped Ni–Fe disulfide indicated low overpotential and Tafel slope. [ABSTRACT FROM AUTHOR]