Curing behavior and toughening performance of epoxy resins containing hyperbranched polyester

The effects of the hyperbranched polyester with hydroxyl end groups (HBPE‐OH) on the curing behavior and toughening performance of a commercial epoxy resin (diglycidyl ether of bisphenol A, DGEBA) were presented. The addition of HBPE‐OH into DGEBA strongly increased its curing rate and conversion of epoxide group due to the catalytic effect of hydroxyl groups in HBPE‐OH and the low viscosity of the blend at curing temperature. The improvements on impact strength and critical stress intensity factor (or fracture toughness, K_1c) were observed with adding HBPE‐OH. The impact strength was 8.04 kJ m^?1 when HBPE‐OH reached 15 wt% and the K_1c value was approximately two times the value of pure epoxy resin when HBPE‐OH content was 20 wt%. The morphology of the blends was also investigated, which indicated that HBPE‐OH particles, as a second phase in the epoxy matrix, combined with each other as the concentration of HBPE‐OH increased. Copyright © 2004 John Wiley & Sons, Ltd.     

Chemo-bio catalysis using carbon supports: application in H2-driven cofactor recycling

Heterogeneous biocatalytic hydrogenation is an attractive strategy for clean, enantioselective C X reduction. This approach relies on enzymes powered by H₂-driven NADH recycling. Commercially available carbon-supported metal (metal/C) catalysts are investigated here for direct H₂-driven NAD⁺ reduction. Selected metal/C catalysts are then used for H₂ oxidation with electrons transferred via the conductive carbon support material to an adsorbed enzyme for NAD⁺ reduction. These chemo-bio catalysts show improved activity and selectivity for generating bioactive NADH under ambient reaction conditions compared to metal/C catalysts. The metal/C catalysts and carbon support materials (all activated carbon or carbon black) are characterised to probe which properties potentially influence catalyst activity. The optimised chemo-bio catalysts are then used to supply NADH to an alcohol dehydrogenase for enantioselective (>99% ee) ketone reductions, leading to high cofactor turnover numbers and Pd and NAD⁺ reductase activities of 441 h⁻¹ and 2347 h⁻¹, respectively. This method demonstrates a new way of combining chemo- and biocatalysis on carbon supports, highlighted here for selective hydrogenation reactions.

Heterogeneous chemo-bio catalytic hydrogenation is an attractive strategy for clean, enantioselective C X reduction.     

A Self-Diffraction Temporal Filter for Contrast Enhancement in Femtosecond Ultra-High Intensity Laser

We demonstrated a nonlinear temporal filter based on the self-diffraction(SD) process. Temporal contrast enhancement, angular dispersion and spectrum broadening properties of the SD process are investigated in experiment and simulation. Driven by spectral phase well compensated laser pulses with bandwidth of 28 nm,the filter produced clean pulses with a temporal contrast higher than 1010 and excellent spatial profile, the spectrum of which was smoothed and broadened to 64 nm. After implementing this filter into a home-made30 TW Ti:sapphire amplifier, temporal contrast of the amplified pulses was enhanced to 1010 within the time scale of-400 ps.     

磺化嵌段型共聚物在质子交换膜燃料电池中的应用

燃料电池是以碳氢化合物为燃料的一种新型、清洁的发电装置,而其中的质子交换膜燃料电池由于具有可快速启动的优点而可应用于机动车等领域。所用的质子交换膜需要具有高的质子传导性、低的甲醇/水渗透性、好的机械和热稳定性以及合适的价格等特点,但目前已经工业化的Nafion膜并未能全部满足上述要求。为了解决这些问题,目前已经开发了多种新的质子交换膜。本文对其中的磺化嵌段型聚醚砜、磺化嵌段型聚酰亚胺和苯乙烯基嵌段共聚物在质子交换膜燃料电池中的应用进行了综述,并与Nafion膜和相应的无规共聚物的性能进行了比较。最后展望了嵌段共聚物在质子交换膜领域的发展趋势。     

液晶弹性体刺激形变研究

开发可以通过外部刺激产生机械形变的人工致动材料是一个近年来的研究热点。其中,液晶弹性体因结合了聚合物网络的橡胶弹性和液晶的有序性而具有独特的性质,在热、光、电等的外界刺激下可以产生可逆的形状记忆效应。本文综述了液晶弹性体响应多种外界刺激产生各种形变的行为,主要介绍了有关热致形变液晶弹性体、电致形变液晶弹性体、化学刺激导致形变的液晶弹性体及光致形变液晶弹性体的研究进展,阐述了各类液晶弹性体产生形变的机理包括热致、电致和光致相转变,讨论了影响其响应性能的主要因素,并展望了这一领域的发展前景。     

过硫酸盐活化高级氧化新技术

过硫酸盐在热、光、过渡金属催化等条件激活下产生强氧化性的硫酸根自由基·SO₄^-。基于·SO₄^-的过硫酸盐活化“高级氧化技术”在环境污染治理领域的应用,是刚刚发展起来的崭新的研究方向,具有广阔的应用前景。本文在分析其基本原理的基础上,综述了过硫酸盐活化技术在国内外土壤地下水有机污染原位修复、难降解有机废水处理等环境污染治理方面的研究进展,并就存在问题进行了研究展望。     

量子点在生物化学传感中的应用研究进展

综述了荧光量子点在生物化学传感中的研究应用进展,重点介绍离子、酶以及糖类的传感,并展望了其发展趋势和应用前景。     

氢化物原子荧光法测定化妆品中的汞

采用微波消解技术对化妆品样品进行消解,用氢化物原子荧光法测定样品中的汞.改变仪器条件及溶液浓度进行试验,确定最佳试验参数.汞浓度在0～20μg/L范围内与原子荧光强度呈良好的线性关系,相关系数为0.9997,方法检出限为0.0005μg/L.对眼影和润肤露样品进行加标回收试验,回收率为95%～100%.与浸提法相比,微波消解法提取出的汞完全且损失少.     

HPLC/MS测定蒲公英颗粒中绿原酸、咖啡酸和阿魏酸的含量

建立了同时测定蒲公英颗粒中绿原酸、咖啡酸和阿魏酸3种酚酸物质含量的HPLC-MS方法.样品用含5%甲酸的甲醇溶液超声提取后,在Zorbax Eclipse XDB-C18(2.1mm×150mm,5μm)色谱柱上,以含0.2%甲酸的水(A)-乙腈(B)体系为流动相,进行梯度洗脱,线性梯度洗脱程序为:Omin,5%B;1.5min,10%B;10min,40%B;流速:0.25mL/min;在ESI正离子模式下,采用选择性离子监测方法进行检测.结果显示,绿原酸、咖啡酸和阿魏酸的线性范围分别为0.050～20.0、0.030～20.0和0.100～20.0μg/mL,检出限分别为0.010、0.006和0.020μg/mL.平均加标回收率为96.4%～101.6%,相对标准偏差为1.7%～3.3%.样品在10 h内测定基本不变,可用于蒲公英颗粒的质量控制.     

应用极化水分子模型研究单分子层受限水的介电性质

受限条件下水的介电性质因测量极具挑战,其在诸多电化学过程与反应输运过程中如何扮演关键角色从未被定量地澄清.本工作利用平衡态分子动力学模拟和受限体系介电性质计算方法,系统性地探索了0.65 nm限域尺寸、5×10⁸ Pa限域压强、不同温度条件下单分子受限冰和受限水的介电性质.详细比较了恒定偶极矩SPC/E水分子模型和可极化的SWM4-NDP水分子模型在描述受限冰、水结构与介电性质上的优劣势,包括统计分析SWM4-NDP模型模拟的单分子层受限水和受限冰的瞬时分子偶极矩概率密度分布,计算每个模拟体系的静态结构因子、静态偶极空间关联函数、静态介电常数、体系偶极时间关联函数和德拜弛豫时间.首次发现了极化水分子模型描述的低维度受限水和受限冰的奇异分子极性变化,并观察到两种模型描述静态结构性质的效果相当, SWM4-NDP模型对于静态介电常数描述的优势会因受限条件的增强而被大幅削减.但在受限水介电极化弛豫动力学性质描述上SWM4-NDP模型明显优于SPC/E模型.我们推断SWM4-NDP模型在探索受限水结构相变动力学以及受限体系离子输运和溶剂化动力学等过程的模拟研究中是比SPC...