Advanced Materials Research Vols. 287-290

Abstract: A series of novel polyethylene glycol derivates was synthesized by esterification of chloroacetic acid with polyethylene glycol.The PEG-5-FU conjugates were characterized by FT-IR, ¹H-NMR and UV spectroscopy. The result showed that 5-FU was successfully connected to the ends of PEG ester. Drug content of PEG₂₀₀₀-5-FU conjugate achieved 17.4%. As the molecular weight of PEG increased, the water solubility of prodrugs improved. When the molecular weight of PEG reached 2000, the conjugate had the best water solubility and the highest drug release rate.

Abstract: Nitrite removal from municipal wastewater is mandatory considering the treated wastewater reuse. Removal on an anion exchanger leads to simple wastewater treatment installations, easy to handle, to exploit and to maintain. This study reports on the performance of anion exchange resin on removing nitrite from synthetic solutions. Equilibrium data could be well fitted using the Langmuir model, confirming ion exchange without any parallel mechanisms. Kinetic study of the process is evaluated using the shrinking core model and the dominant rate mechanism is estimate.

Abstract: The characterization of the aging behavior of raw natural rubber (NR) coagulated by microorganisms (NR-m) was performed on a rubber processing analyzer (RPA) by tests of frequency sweep, strain sweep and stress relaxation, respectively. With the prolongation of the aging time, the storage modulus (G'), storage torque (S'), complex viscosity (η^*) and stress relaxation time of raw NR-m decreased while the damping factor (tanδ) were increased. As the oscillation frequency was increasing, the G' rose gradually but the tanδ decreased. The η^* diminished over the whole range of frequency shear rate (γ_ƒ) values. Its change remained all almost the same at low strain shear rate (γ_s) but began to decrease sharply when the rate reached a higher value. The S' soared up in the region of less than 10°, but began to slow down after that point.

Abstract: Vacuum evaporation is usually utilized to remove volatile impurities in metallurgical grade silicon to prepare solar grade silicon by metallurgical routes. Especially phosphorus needs to be removed by vacuum evaporation. And the removal efficiency of impurities strongly influenced the quality and performance of products. In this paper, the removal efficiency of impurities is studied by using different raw material. The results indicated that the content of impurities in raw material had deep effect on the removal efficiency of vacuum evaporation. The high quality product can be obtained by vacuum evaporation only once from raw materials with the lower content of impurities whereas it is not for high content of impurities in raw material. This is due to the vapor-liquid equilibrium in the vacuum furnace. The impurities can be removed effectively by vacuum evaporation many times.

Abstract: The structures of tris(8-hydroxyquinoline) aluminum (Alq3) and its difluorinated derivatives were optimized for the ground state at the B3LYP/6-31G* level and for the excited-state at the CIS/6-31G* level. At the same time, the absorption and emission spectra based on the above structures were calculated by the time-dependent density functional theory (TD-DFT) using the PBE0 method with the 6-31G* set. A significant red shift was predicted for 3,5-difluoro-substituted Alq3 while a significant blue shift for 4,6-difluoro-substituted Alq3. In addition, the reorganization energies for electron carriers (λe) were predicted and it was found that the derivatives are potential materials for electron transport.

Abstract: Waterborne polyurethane emulsions were synthesized with isophorone diisocyanate(IPDI), dihydromethyl propionic acid(DMPA) and poly-ε-caprolactone glycol(PCL), and then reacted with hydroxy-ethyl acrylate(HEA) and 3-aminopropyltriethoxylsilane(APTES) to cap the terminal -NCO groups. The polyurethane emulsions were used to copolymerize with acrylates to synthesize the modified waterborne polyurethane-acrylate hybrid emulsions. The structure, thermal stability and crystallinity of modified polyurethane were studied by FTIR, TG, XRD and the mechanical properties of modified polyurethane films was also investigated. The results show that crystallization of the modified waterborne polyurethane decreases and thermal stability is improved. When the mass fraction of acrylate is 20% and APTES content is 15%, tensile strength of the modified polyurethane films can reach 23.9MPa and elongation at break is 247%.

Abstract: Biodegradable aliphatic polyesteramides were synthesized from ε-caprolactone and 6-aminocaproic acid by melt-polycondensation method. FTIR, 1H-NMR, DSC, WAXD, TG, and tensile testing were used to characterize the polyesteramides. With the increase in 6-aminocaproic acid content, the melting temperature, thermal degradation temperature and tensile strength at break increased accordingly. The ester bond decomposes at lower temperature, and then the amide bond decomposes at higher temperature.

Abstract: Crystal structure of an aromatic polysulfones containing biphenylene units was elucidated using diffraction simulation technique extracted from X-ray data and interfaced with computational modeling. The chain conformations and configurations were derived from a synthesized oligomer and several analogous structure of past studies. It was found that the polymer adopt an orthorhombic Cmcm with the adjacent aromatic rings attached to the sulfone linkage orthogonal to each other whilst the biphenylene unit are coplanar. The chain conformation and crystal systems are consistent with the analogous polymer containing wholly uniphenylene unit.

Abstract: A ternary Li-Mg-B alloy (64%Li, 4%Mg and 32%B, all compositions are reported as weight percent in this paper) foil was prepared and its phase structure and discharge behavior were investigated. The main phases existing in the alloy included Li₅B₄, Li₃Mg₇, LiB and Li. Coupled with LiNO₃-KNO₃ eutectic electrolyte and MnO₂ cathode, the anode exhibited great potential in the intermediate temperature lithium batteries. At temperatures above 200°C, two steady voltage plateaus were obtained at near 3V and 2.7V, and the cell displayed an open-circuit voltage exceeding 3.2V. The experimentally measured capacity of the Li-Mg-B alloy was 5427C·g^-1 at 200°C, which was higher than that of LiB alloy (70%Li). Adding magnesium to LiB alloy could lower the cost of anodes without capacity loss.

Abstract: We used high-purity multicrystalline silicon prepared by metallurgical method for the study of directional solidification. The optical microscope was used to observe the etch pits on the surface of silicon wafers, and we calculated their dislocation density. The result showed the space distribution of dislocation density presented “V” shape for each ingot produced at different drop-down rates. The dislocation density of slicon ingots followed the order 10<20<30<40μm/s. The high-resolution glow discharge mass spectroscopy was used to analyze the concentration of transition metal impurities. The macro-morphology of vertical-section of silicon ingots growth at different drop-down rates was observed. The x-ray diffraction measurement was performed to analyze the crystallographic orientations of the silicon ingot growth at 20μm/s, which was a better drop-down rate for producing high-quality multicrystalline silicon.