Effect of Molecular Weight on the Properties of Poly（butylene succinate）

Poly（butylene succinate） （PBS） with different molecular weight was synthesized from 1, 4-butanediol and succinic acid by direct melt condensation. The synthesized PBS was identified by IH-NMR and FTIR spectrometry. The molecular weight was calculated from the intrinsic viscosity, and its value was between 20000 and 70000. The crystallization behavior and crystal morphology as function of molecular weight were investigated by DSC and PLM, respectively. The mechanical properties and hydrolytic degradation behaviors related with change of molecular weight were also studied in this work. The results demonstrated that the properties of PBS were determined by both molecular weight and crystallization properties （crystallinity as well as crystal morphology）. Our work is important for the design and preparation of PBS with proper molecular weight for its practical application.     

Iron-mediated AGET ATRP of styrene and methyl methacrylate using ascorbic acid sodium salt as reducing agent

Atom transfer radical polymerization of styrene(St) and methyl methacrylate(MMA) in bulk and in different solvents using activators generated by electron transfer(AGET ATRP) were investigated in the presence of a limited amount of air using FeCl3·6H2O as the catalyst, ascorbic acid sodium salt(AsAc-Na) as the reducing agent, and a cheap and commercially available tetrabutylammonium bromide(TBABr) as the ligand. It was found that polymerization in THF resulted in shorter induction period than that in bulk and in toluene for AGET ATRP of St, while referring to AGET ATRP of MMA, polymerization in THF showed three advantages compared with that in bulk and toluene: 1) shortening the induction period, 2) enhancing the polymerization rate and 3) having better controllability. The living features of the obtained polymers were verified by chain end analysis and chain-extension experiments.     

Investigation of Hydrolysis in Poly（ethylene terephthalate） by FTIR-ATR

The hydrothermal aging of poly(ethylene terephthalate)(PET) was investigated at 70 95 °C. A new method to investigate the hydrolysis degree of PET by Fourier transform infrared spectroscopy(FTIR) was proposed. The spectra during the hydrothermal aging were measured using attenuated total reflection accessory(ATR). Peak resolving of carbonyl regions was performed, and the ratio of two groups of bands representing carboxylic acids and esters respectively were calculated to show the hydrolysis degree of ester groups in PET. The acid/ester ratio shows exactly the same trend as the average chain scission number per unit mass at various temperatures and thus can be used as a parameter to characterize the hydrolysis and random chain scission of PET. This method related to the hydrolysis mechanism directly, is simple, fast and convenient compared to the traditional methods such as viscometry, end-group titration and size exclusion chromatography(SEC). It may also be useful in hydrolysis characterization of other polyesters.     

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.     

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。     

长江下游下蜀黄土的稀土元素物源判别

通过对长江下游镇江、福家湾、新港、芜湖、福路镇等地区下蜀黄土中稀土元素的研究,结合长江古漫滩堆积物及北方黄土沉积物,对下蜀黄土进行了物源判别,得出：下蜀黄土与长江河漫滩之间的各稀土元素的 DF 值绝大部分小于0．2,表现出在各个稀土元素上与河漫滩的接近程度较大,而与北方黄土接近程度较小;由物源指数 PI 计算得出,新港、福路镇、镇江下蜀黄土 PI 值均在0．2附近,表现出下蜀黄土与河漫滩在稀土元素总体上的相似程度极高,物源判别为长江河漫滩;福家湾下蜀黄土物源判别为北方黄土,北方黄土对其有一定影响。总体上,长江下游下蜀黄土受到北方黄土与河漫滩的影响,其中以长江河漫滩影响为主。     

川芎栽培土壤中重金属镉的动态监测

目的：连续多年监测彭州敖平镇川芎药材栽培土壤中重金属镉的含量,分析其对川芎药材中镉含量的影响。方法根据前期研究结果选取敖平镇部分川芎种植地固定采集样品。按照国家标准方法,采取0～20 cm连续根系土柱和川芎药材。采用火焰法对抽样土壤及川芎药材中镉的含量进行检测分析。结果采样区域内土壤中镉含量均符合国家二级土壤环境质量标准;部分土壤中镉的含量呈明显增长趋势。结论川芎种植土壤中镉含量与环境有较高关联,水泥厂粉尘等污染源是土壤中镉含量增加的重要来源。     

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.     

Effects of acid etching on the structure of PtNi catalyst and total exposed active sites

The integration technology of hydrogen preparation–hydrogen storage not only can utilize hydrogen energy efficiently but also can improve the selectivity of the electrode maximally. In the present work, the structure and composition of the PtNi catalyst was characterized by X-ray diffraction (XRD); and its electrochemical properties, morphology, and surface binding energy were analyzed by cyclic voltammetry (CV) and linear scanning voltammetry (LSV), scanning electron microscopy equipped with energy-dispersive spectrometry (SEM-EDS), and X-ray photoelectron spectroscopy (XPS), respectively. The effects of different acid etching treatments (e.g., etching time, etchant concentration, and etching temperature) on the structure and surface active sites were investigated by the orthogonal experiment. The experimental results reveal that after etching with 0.5 mol/L of perchloric acid for 0.5 h at 60°C, the electrode weight loss of the PtNi catalyst is mainly attributed to the large loss of Ni atoms in film layer. This results in the reduced alloy phase in film layer and the appearance of Pt characteristic diffraction peak. The relative content of Pt on the surface of the film electrode increases significantly, and the total number of active sites also increases correspondingly. The binding energy of Pt4f_7/2 decreases by 0.19 eV, and the number of active sites involved in hydrogen release decreases, indicative of the reduced promotion effect of the PtNi catalyst on hydrogen release.     

Characterization of sequence variation at 30 autosomal STRs in Chinese Han and Tibetan populations

Massively parallel sequencing (MPS) technologies have the ability to reveal sequence variations within STR alleles as well as their nominal allele lengths, which have traditionally been detected by CE instruments. Recently, Thermo Fisher Scientific has updated the MPS-STR panel, named the Precision ID GlobalFiler next-generation sequencing (NGS) STR Panel version 2, with primers redesigned to add two pentanucleotide tandem repeat loci and profile interpretation supported by the Converge software. Using the Ion Chef System, the Ion S5XL System, and the Converge software, genetic variations were characterized within STR repeat and flanking regions of 30 autosomal STR markers in 115 unrelated individuals from two Chinese population groups (58 Tibetans and 57 Hans). Nineteen STRs demonstrated a relative increase in diversity with the variant sequence alleles compared with those of traditional nominal length alleles. In total, 390 alleles were identified by their sequences compared with 258 alleles that were identified by length. Of these 92 sequence variants found within the STR repeat regions, 40 variants were located in STR flanking regions. Additionally, the agreement of the results with CE data was evaluated, as was the ability of this new MPS panel to analyze case-type (11 samples) and artificially degraded samples (seven samples in triplicate). The results generated from this study illustrate that extensive sequence variation exists in commonly used STR markers in the selected population samples and indicate that this NGS STR panel has the potential to be used as an effective tool for human forensics.