Microstructure characterization of short-chain branching polyethylene with differential scanning calorimetry and successive selfnucleation/annealing thermal fractionation

A series of the copolymers of ethylene with 1-hexene(M1–M9) synthesized by metallocene catalyst Et[Ind]2ZrCl2/MAO was studied by differential scanning calorimetry and successive self-nucleation and annealing(SSA) thermal fractionation. The distribution of methylene sequence length(MSL) in the different copolymers was determined using the SSA method. The comonomer contents of samples M4 and M5 are 2.04 mol% and 2.78 mol%, respectively. Both M4 and M5 have low comonomer content and their MSL distribution profiles exhibit a monotonous increase trend with their MSL. The longest MSL of M5 is 167, and its corresponding molar percent is 43.95%, which is higher than that of M4. Moreover, the melting temperature(Tm) of M5 is also higher than that of M4. The comonomer contents of samples M7, M8, and M9 are 8.73 mol%, 14.18 mol% and 15.05 mol%, respectively. M7, M8, and M9 have high comonomer contents, and their MSL distribution profiles display unimodality. M7 has a lower peak value of 33 and a narrow MSL distribution, resulting in a Tm lower than that of M8 and M9. The MSL and its distribution are also key points that influence the melting behavior of copolymers. Sometimes, MSL and its distribution of copolymers have a greater impact on it than the total comonomer contents, which is different from traditional views.     

两种异马来二氰基二硫烯镍(II)-取代苄基喹啉鎓盐的制备及其光谱性质和晶体结构

以甲醇为溶剂,将异马来二氰基二硫烯酸钾[K2(i-mnt)]和六水氯化镍分别与溴化4-溴苄基喹啉盐([4-BrBzQl]Br)或溴化4-硝基苄基喹啉盐([4-NO2BzQl]Br)直接反应,得到两种新的离子对配合物[4-BrBzQl]2[Ni(i-mnt)2](1)和[4-NO2BzQl]2[Ni(i-mnt)2](2);测定了其红外光谱和紫外-可见光谱,并利用X射线衍射表征了配合物1的晶体结构.结果表明,配合物[4-BrBzQl]2[Ni(i-mnt)2]为三斜晶系,P-1空间群,其每个不对称单元含半个[Ni(i-mnt)2]2-阴离子和1个[4-BrBzQl]+阳离子,晶体中的阴、阳离子通过静电作用和C-H…S、C-H…N氢键作用形成网络结构.     

CM⁃Phos配体在钯催化交叉偶联反应中的应用

本文综合评述了近年来2-[2-(二环己膦基)苯基]-1-甲基-1H-吲哚(CM-Phos)膦配体及其衍生物在钯催化的交叉偶联反应中的应用, 主要根据不同种类的交叉偶联反应进行系统性分述, 并对该领域的发展前景进行了展望.     

氧化石墨烯调控钼酸铋在可见光下选择性光催化降解环境水中的抗生素

以氧化石墨烯(GO)作为增强光催化剂活性的调节剂, 采用一步水热法制备钼酸铋/氧化石墨烯(Bi₂MoO₆/GO)异质结光催化剂, 其可见光响应拓展至570 nm, 带隙能降至2.56 eV. 当m_Bi2MoO6/m_GO=100∶1时, Bi₂MoO₆/GO(100∶1)光催化剂在可见光的辐射下, 对水溶液中四环素和喹诺酮类抗生素选择性的高效催化降解去除能力为Bi₂MoO₆的2.1倍. Bi₂MoO₆/GO(100∶1)光催化剂活性的提高依赖于范德华力作用下的二维Bi₂MoO₆纳米片-二维GO纳米片界面的紧密接触. 有效的界面接触改善了光生电子的转移和光生载流子的分离. 自由基清除实验结果表明, ?OH起主要作用. 结合高效液相色谱-质谱(HPLC-MS)法对降解产物的分析, 提出了不同光催化剂催化降解恩诺沙星具有相似的降解途径和降解产物.     

电光高分子材料的最新研究进展

电光高分子材料由于其在光电子信息领域的潜在应用前景已得到了广泛关注和深入研究.本文在简要介绍电光效应及其材料等相关知识的基础上,综述了最近几年来电光高分子材料的研究进展,主要包括生色团的设计与合成,以及掺杂型、侧链型、主链型、交联型、互穿网络型和树枝型等聚合物材料体系的设计与合成.     

Chemoselective hydrogenolysis of tetrahydrofurfuryl alcohol to 1,5-pentanediol over Ir-MoOx/Si02 catalyst

In this work, MoOx promoted Ir/SiO2 catalysts were prepared and used for the selective hydrogenolysis of tetrahydrofurfuryl alcohol （THFA） to 1,5-pentanediol in a continuous flow reactor. The effects of different noble metals （Ir, Pt, Pd, Ru, Rh）, supports and Ir contents were screened. Among the investigated catalysts, 4 wt%Ir-MoOx/SiO2 with a Mo/Ir atomic ratio of 0.13 exhibited the best catalytic performance. The synergy between Ix particles and the partially reduced isolated MoOx species attached on them is essential for the excellent catalytic performance of Ix-MoOx/SiO2. The catalyst exhibited a better hydrogenolysis efficiency of THFA with the selectivity of 1,5-pentanediol of 65%-74% at a conversion of THFA of 70%-75% when the initial THFA concentration is ranging from 20 wt% and 40 wt%. And higher system pressure was also in favor of the conversion of THFA. During a stability test, the conversion of THFA and 1,5-pentanediol yield over Ix-MoOz/SiO2 decreased with reaction time, which can be explained by the leaching of Mo species during the reaction.     

Pt（111）电极上O2与OHad的吸脱附及氧还原反应动力学

研究了Pt（111）电极在0．1mol／LHClO4溶液中O2吸附与OHad脱附及氧还原反应的动力学．研究发现OHad的可逆吸脱附速率很快;在氧还原的动力学或动力学与传质混合控制区,恒电位下氧还原的电流随反应时间缓慢衰减,在转速较大,扫速较慢的情形下正向扫描过程中氧还原的电流总是明显低于逆向扫描的电流;Pt／0．1mol／LHClO4从无O2切换到O2饱和时,其开路电位迅速从0．9V增加到1．0V．结果表明,Pt（111）电极上O2解离生成OHad速率很快,ORR过程中OHad会在表面缓慢积累,氧还原反应的动力学主要由反应 OHad＋H^＋＋e→←H2O的平衡热力学决定．     

光化学柱后衍生–高效液相色谱法测定婴幼儿营养米粉中的黄曲霉毒素B1

建立婴幼儿营养米粉中黄曲霉毒素B1的高效液相色谱荧光检测器测定方法。样品以甲醇–水(体积比70∶30)溶液匀质提取,过黄曲霉毒素B1免疫层析亲和柱净化,经CNW Athena C18色谱柱分离和光化学柱后衍生反应器衍生后,用带有荧光检测器的高效液相色谱仪测定。采用峰面积外标法定量黄曲霉毒素B1含量。黄曲霉毒素B1在0～10μg/L的浓度范围内线性关系良好,相关系数为0.999 8,检出限为0.25μg/kg。在3个添加水平下加标回收率为97.7%～106.9%,测定结果的相对标准偏差为1.7%(n=6)。该方法的灵敏度、准确度、精密度均符合黄曲霉毒素B1的检测技术要求,适用于婴幼儿营养米粉中黄曲霉毒素B1的日常检测。     

乙酰丙酮钌催化硝基苯氢转移氢化制苯胺

以自制的乙酰丙酮钌配合物（Ru(acac)3）为催化剂,甲酸钠为氢供体,十六烷基三甲基溴化铵为乳化剂,研究了水溶液中催化硝基苯氢转移氢化制苯胺的工艺。 确定了适宜反应条件为：甲酸钠和硝基苯摩尔比为2∶1,反应温度80 ℃,反应时间4.0 h,Ru(acac)3用量为硝基苯质量的4%。 硝基苯的转化率和苯胺产率分别为100%和96.65%,表明Ru(acac)3对硝基苯氢转移氢化制苯胺具有优异的催化作用。     

毛细管电泳法评价细胞色素c与单链脱氧核糖核酸库的相互作用

以细胞色素c(Cyt c)为碱性蛋白质模型,建立了毛细管电泳评价Cyt c与3种不同链长的单链脱氧核糖核酸(ssDNA)库相互作用的评价方法,研究了离子强度对Cyt c与ssDNA库相互作用的影响。比较了Cyt c与含有20、40和60个随机碱基序列的3种不同链长的ssDNA库的作用及基于未涂层毛细管和涂层毛细管的毛细管区带电泳方法。因碱性蛋白质在未涂层毛细管管壁上存在吸附,因此利用未涂层毛细管区带电泳不能区别3种ssDNA库与其作用的差异。利用涂层毛细管电泳法,在压力辅助的反向电压下,根据游离ssDNA库的峰面积变化可比较3种ssDNA库与细胞色素c的相互作用差异。结果表明,含有20个随机寡核苷酸链长的ssDNA库与Cty c的作用最强。此外,NaCl浓度显著影响Cyt c与ssDNA60库的作用。在优化的实验条件下,0.02 mol/L NaCl有利于两者的相互作用。调节盐浓度可抑制非特异性静电作用,能提高碱性蛋白质适配体的单轮筛选效率。利用未涂层毛细管电泳分析复合物及游离ssDNA库的峰面积变化,可优化有利复合物形成的盐浓度。