Institute of Chemistry
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Synthesis and Multi-Stimuli-Responsive Behavior of Poly(N,N-dimethylaminoethyl methacrylate) Spherical Brushes under Different Modes of Confinement in Solution
No full textWe report the synthesis and solution behavior of photo-, temperature-, pH-, and ion-responsive weak polyelectrolyte spherical brushes under different modes of confinement. The spherical brushes were prepared by copolymerization of N,N-dimethylaminoethyl methacrylate (DMAEMA) and 7-(2-methacryloyloxyethoxy)-4-methylcoumarin anchored to silica nanoparticles via surface-initiated atom transfer radical polymerization. The photo-cross-linking and reversibility of the nanoparticle-attached coumarin entities are detected by UV-visible spectroscopy and dynamic light scattering (DLS). The cross-linking density of poly(DMAEMA) (i.e., PDMAEMA) brushes could be easily controlled by alternating irradiation at wavelengths of 365 and 254 nm. Moreover, solution behavior under different pH levels and ionic strengths is systematically investigated in the PDMAEMA brush polyelectrolyte chains confined only by a hard core, the cross-linked PDMAEMA brush polyelectrolyte chains confined by a hard core and cross-linking points, and the corresponding hollow nanocapsules after removal of silica by etching-polyelectrolyte chains confined only by cross-linking points. These three models represent the different modes of confinement. DLS results indicate that the volume phase transition temperatures of the three models shift to lower temperatures with the increase in pH. The highest temperature is afforded to phase transition for hollow nanocapsules in solution, followed by the cross-linked PDMAEMA brushes. The hydrodynamic radius of the polyelectrolyte brush systems obviously decreases with the increase in ionic strength of the solution when adjusted by NaCl
Tri-chromatic white-light emission from a single-phase Ca9Sc(PO4)(7):Eu2+, Tb3+, Mn2+ phosphor for LED applications
No full textA series of single-phase Ca9Sc(PO4)(7):Eu2+, Tb3+, Mn2+ phosphors for UV excitations were synthesized by a high-temperature solid-state reaction. Energy transfer from Eu2+ -> Tb3+ and Eu2+ -> Mn2+ in a Ca9Sc(PO4)(7) sample is a feasible route to realize color-tunable emission because Ca9Sc(PO4)(7) single-doped Eu2+/Tb3+/Mn2+ emit blue, green and red light, respectively. Most of the white light region in the CIE chromaticity diagram has been realized in Ca9Sc(PO4)(7):Eu2+, Tb3+, Mn2+ phosphors. Warm white light including the points of (0.337, 0.331), (0.353, 0.355) and (0.358, 0.327) close to day light (0.33, 0.33) with CCT of 5285 K, 4719 K and 4333 K is obtained, respectively
Colorless metallodithiolene oligomers and polymers with intense near- and mid-infrared absorption
No full textReported herein are the syntheses and properties of a series of multi-nuclear metallodithiolene complex oligomers (5, 6 and 7) and a homologous polymer (8). The Ni/Pd-dithiolene complexes 5, 6 and 7 are characterized by intense absorption in the spectral region of 1000-1800 nm with a high molar absorption coefficient (e.g., 10(5) M-1 cm(-1) at 1257 nm for 7). Complex polymer 8 is readily soluble in common organic solvents and shows remarkably broad and intense absorption in the entire near- and mid-infrared spectral region (800 nm-25 mu m). The films of these metallodithiolene materials exhibit good visual transparency or extremely weak absorption in the visible region, making them potentially useful as excellent colourless infrared absorbers
Synergistic effect of PLA-PBAT-PLA tri-block copolymers with two molecular weights as compatibilizers on the mechanical and rheological properties of PLA/PBAT blends
No full textTwo types of polylactide-poly(butylene adipate-co-terephthalate)-polylactide (PLA-PBAT-PLA) tri-block copolymers with different molecular weights (CP1 and CP2) were synthesized as compatibilizers for PLA/PBAT blends. Synergistic effects of CP1 and CP2 on the mechanical and rheological properties of the blends have been studied in detail. The addition of small amounts of CP1 and CP2 remarkably increased the elongation at the break point. 0.5 and 0.5 wt% of CP1 and CP2 led to an increase of elongation by over eightfold. Thermal, morphological and rheological analyses showed that addition of CP1 and CP2 increased the miscibility and interfacial bonding strength between PLA and PBAT, in addition to decreasing the melt viscosity. It was thought that the low-molecular-weight compatibilizer CP1 with high mobility would have a positive effect during the transportation of the high-molecular-weight CP2 from the matrix to the interface. In addition, CP2 played a key role in improving the interaction at the interface
[ONNO]-type oxovanadium(V) complexes containing amine pyridine bis(phenolate) ligands: synthesis, characterization and catalytic behavior for ethylene (co)polymerization
Get PDFA series of oxoyanadium(V) complexes bearing dianionic [ONNO] chelate ligands 2-[bis(3-R1-5-R2-2 hydroxybenzyl) aminomethyllpyridine (2a: R-1 = tBu, R-2 =H; 2b: R-1 =CF3, R-2 = H; 2c: R-1 =OCH3, R-2=H; 2d: R-1 = R-2 = Bu-t) and 2-[bis(3-R(1)5-R-2-hydroxybenzyl) aminoethyl]pyridine (2e: R-1= R-2 = tBu) have been synthesized by reacting VO(OnPr)(3) with 1.0 equiv. of the ligands in CH2Cl2. All these complexes were characterized by H-1, C-13, V-51 NMR spectra and elemental analysis. X-ray structural analysis for 2d revealed a six-coordinate distorted octahedral geometry around the vanadium center in the solid state. It was observed that these complexes existed as a mixture of two isomers, and the main isomer had the oxo moiety in trans configuration to the tripodal nitrogen atom. In the presence of Et(2)AICI and CCI3COOEt, these complexes displayed high catalytic activities for ethylene polymerization even at elevated reaction temperature, depending on ligand structures. The resultant polymers possessed high molecular weights and unimodal molecular weight distributions, indicative of a single active site nature. In addition, copolymerizations of ethylene and norbornene using precatalysts 2a e were also investigated, and the observed catalytic activity was nearly comparable with that for ethylene homopolymerization. When the concentration of comonomer in the feed amounted to 3.0 mol/L, a NBE incorporation up to 41.5% could be achieved. Other reaction parameters that influenced the polymerization behavior, such as reaction temperature and Al/V (molar ratio), are also examined in detail. (C) 2014 Elsevier B.V. All rights reserved
Effect of carbon black on improving thermal stability, flame retardancy and electrical conductivity of polypropylene/carbon fiber composites
Get PDFIn this work, carbon black (CB) was introduced into polypropylene/carbon fiber (PP/CF) composite to fabricate multifunctional composites with the improved thermal stability, flame retardancy and electrical conductivity. The morphology investigation showed that one-dimensional CF and zero-dimensional were well dispersed in the PP matrix, and the multistage structure was formed in PP matrix. Compared to pristine PP, the maximum weight loss temperature under air atmosphere was enhanced by 79 degrees C. The peak value of the heat release rate measured by a cone calorimeter was significantly reduced by 70%, and the total heat release decreased from 198 to 166 MJ/m(2). The dramatically enhanced flame retardancy of PP composites was attributed to the formation of a strong three-dimensional (3D) network structure in PP matrix where one-dimensional CF acted as bridges connecting individual zero-dimensional CB, and the accelerated oxidation crosslinking reaction of PP radicals by CB and CF. Furthermore, the electrical conductivity of PP composites was significantly enhanced to 7.8 S/m due to the formation of 3D conductive pathways from CB and CF within the matrix. (C) 2015 Elsevier Ltd. All rights reserved
胶体离子超级电容器
Get PDF超级电容器具有功率密度大、循环寿命长等优点,但同时面临着能量密度低等缺点.胶体离子超级电容器是最近开发的一种新型赝电容器,同时具有高功率密度和高能量密度的特点.胶体离子超级电容器能够充分利用多价态金属阳离子的多电子氧化还原反应,完全释放储存的潜在电能,从而提高超级电容器的能量密度.由于胶体离子的存在,缩短了电子、离子的扩散长度,加快了氧化还原反应动力学,从而保持高的功率密度.本文主要介绍胶体离子超级电容器的发展过程、最新研究进展以及需要进一步开展的研究工作,作者希望从一个新的角度去研究发展下一代高性能电化学储能设备,实现新的突破
两性离子聚合物在恶性肿瘤治疗中的应用
Get PDF两性离子聚合物是一类同时具有酸性和碱性基团的聚合物,在特定p H环境以两性离子的形式存在.两性离子聚合物以水化性能强、抗细菌黏附能力显著、可电荷翻转及易化学修饰等优异性能引起了人们的广泛关注.本文主要根据两性离子聚合物的结构进行分类,并对其在恶性肿瘤的早期诊断和治疗领域的研究进行了分析和总结,展望了两性离子聚合物的发展前景
乳液聚合接枝聚苯乙烯/多壁碳纳米管复合材料的制备及性能研究
No full text采用乳液聚合的方法制备了多壁碳纳米管接枝聚苯乙烯(MWNTs-g-PS)聚合物,然后与聚苯乙烯(PS)熔融共混制得MWNTs-g-PS/PS复合材料。红外光谱分析(FTIR)证实了PS在MWNTs上的接枝反应的发生,透射电镜(TEM)照片显示PS可以有效地接枝到MWNTs上,并且分布比较均匀。通过对样品的热性能进行研究,得出纯的多壁碳纳米管具有良好的热稳定性,基本无失重。MWNTs-g-PS在100~500℃范围内的失重是由于MWNTs-g-PS表面的PS的热分解而形成的。通过扫描电子显微镜(SEM)对MWNTs在PS基体中的分散状态进行研究。MWNTs-g-PS在PS基体中的分散情况比纯MWNTs在PS集体中分散情况好得多。这是由于PS链段在MWNTs表面的接枝包覆,一方面克服了碳纳米管分子间范德华力的作用,另一方面提高了MWNTs与PS之间的相容性,从而提高了MWNTs在PS基体中的分散性
键合靶向纳米胶束对脑胶质瘤细胞的组织相容性和靶向性
No full text目的:探讨转铁蛋白受体的单克隆抗体(OX26)与聚乳酸聚乙二醇(PEG-PLA)键合靶向纳米胶束(copolymer/OX26)的生物相容性和安全性,阐明其作为脑胶质瘤靶向治疗载体的可行性。方法:体外培养C6胶质瘤细胞,用不同浓度(10.0、20.0、40.0和80.0mg·L-1)纳米胶束作为实验组,不含胶束的培养液作为对照组;台盼蓝染色法检测靶向纳米胶束对胶质瘤C6细胞的增殖抑制作用;流式细胞术检测靶向纳米胶束作用后C6胶质瘤细胞凋亡和细胞周期变化;激光共聚焦显微镜观察肿瘤细胞对靶向胶束的摄入情况。结果:与对照组比较,OX26靶向纳米胶束作用后C6细胞数无明显改变(P>0.05),各组细胞凋亡率和细胞周期细胞比例差异亦无统计学意义(P>0.05);靶向纳米胶束组细胞内的荧光强度明显高于空白胶束组和空白对照组(P<0.05),并且这种作用随药物作用时间和浓度的增加而增加。结论:OX26靶向纳米胶束对C6细胞增殖和凋亡无影响,键合OX26提高了C6细胞对胶束的摄入量