Covalent anionic copolymer coatings with tunable electroosmotic flow for optimization of capillary electrophoretic separations

We present a method for finely adjustable electroosmotic flow (EOF) velocity in cathodic direction for the optimization of separations in capillary electrophoresis. To this end, we use surface modification of the separation fused silica capillary by the covalently attached copolymer of acrylamide (AM) and 2-acrylamido-2-methyl-1-propanesulfonate (AMPS), that is, poly(AM-co-AMPS) or PAMAMPS. Coatings were formed by the in-capillary polymerization of a mixture of the neutral AM and anionic AMPS monomers premixed in various ratios in order to control the charge density of the copolymer. EOF mobility varies in the 0 to ∼40 × 10⁻⁹ m² V⁻¹ s⁻¹ interval for PAMAMPS coatings ranging from 0 to 60 mol.% of charged AMPS monomer. For EOF in PAMAMPS-treated capillaries, we observed (i) a negligible dependence on pH in the 2–10 interval, (ii) a minor variance among background electrolytes (BGEs) in function of their components and (iii) its standard decrease with increasing ionic strength of the BGE. Interest in variable cathodic EOF was demonstrated by the amelioration of separation of two kinds of isomeric anionic analytes, that is, monosaccharides phosphates and helquat enantiomers, in counter-EOF mode.     

Microchip electrophoretic protein separation using electroosmotic flow induced by dynamic sodium dodecyl sulfate-coating of uncoated plastic chips

Separation of sodium dodecyl sulfate (SDS)-protein complexes is difficult on plastic microchips due to protein adsorption onto the wall. In this paper, we elucidated the reasons for the difficulties in separating SDS-protein complexes on plastic microchips, and we then demonstrated an effective method for separating proteins using polymethyl methacrylate (PMMA) microchips. Separation difficulties were found to be dependent on adsorption of SDS onto the hydrophobic surface of the channel, by which cathodic electroosmotic flow (EOF; reversed flow) was generated. Our developed method effectively utilized the reversed flow from this cathodic EOF as a driving force for sample proteins using permanently uncoated but dynamic SDS-coated PMMA microchips. High-speed (6 s) separation of proteins and peptides up to 116 kDa was successfully achieved using this system.     

Effect of formulation of silica‐based solution on corrosion resistance of silicate coating on hot‐dip galvanized steel

Several silica‐based solutions with 50 g/l of SiO₂ were prepared from sodium silicate solutions and silica sol; the silicate conversion coatings were obtained by immersing hot‐dip galvanized steel sheets in these solutions. These solutions were characterized using high‐resolution transmission electron microscopy and ²⁹Si nuclear magnetic resonance; the morphology of the coatings was observed by SEM and atomic force microscopy while the corrosion resistance was evaluated by electrochemical measurements as well as neutral salt spray tests. The results show that the coatings obtained from the single silica sol solution had poor adhesion and the coating obtained from the sodium silicate solution with low SiO₂/Na₂O molar ratio was uneven. By adding the silica sol to the silicate solution with low molar ratio, uniform coatings with better protection property were obtained. According to the results of ²⁹Si nuclear magnetic resonance spectra, the effects of the distribution of silicate anions with various polymerization degrees in the silica‐based solutions on the microstructure and corrosion resistance of the silicate coatings are discussed. Copyright © 2016 John Wiley & Sons, Ltd.     

2,4-二氯苯甲酸改性饱和聚酯的合成及其聚氨酯阻燃涂料

用2,4-二氯苯甲酸改性三羟甲基丙烷制得含氯的多元醇中间体（NHDB）,用改性的中间体合成含氯的聚酯。用红外、核磁表征了中间体和聚醇的结构,TGA分析表明,含氯量增高,聚酯热稳性下降。将聚酯同异氰酸酯预聚体常温固化,各种性能良好。阻燃测试表明：含30%的2,4-二氯苯甲酸的聚酯具有自熄功能。提出了阻燃机理。     

高三尖杉酯碱和三尖杉酯碱的合成研究

天然药物高三尖杉酯碱和三尖杉酯碱是从三尖杉植物的叶和茎中分离得到的微量生物碱,是手性化合物。结构上,二者不仅含有一个共同的母核三尖杉碱,酯基侧链的α位也均为手性叔醇。因母核三尖杉碱和酯基侧链较大的空间位阻,两个结构片段的酯化偶联具有较大的挑战性。设计合成位阻较小的侧链中间体是酯化反应发生的关键。因此,化学家们相继合成了结构多样的α-羰基羧酸侧链以及含有杂环的侧链中间体,如四元内酯杂环侧链、四氢呋喃杂环侧链、六氢吡喃杂环侧链、七元内酯杂环侧链,并成功地完成了高三尖杉酯碱、三尖杉酯碱和同属其他活性生物碱的合成。本文基于本课题组的相关研究,根据侧链片段的构建策略和方法,综述了天然药物高三尖杉酯碱、三尖杉酯碱以及其他天然产物的合成研究。不仅总结了近几年来的新进展,还对我国老一辈的科学家们在此方面作出的贡献进行了回顾。     

磷酸锂原位包覆富锂锰基锂离子电池正极材料

本工作通过“碳酸盐共沉淀-沉淀转化-固相反应”方法,实现磷酸锂原位包覆和改性富锂锰基锂离子电池正极材料Li_1.2Mn_0.54Co_0.13Ni_0.13O₂,研究了磷酸锂包覆层的形成过程及其对电化学性能的影响.结果显示,碳酸盐前驱体经沉淀转化反应原位形成磷酸镍包覆层,与锂源混合煅烧,最终转化为厚度小于30 nm的磷酸锂包覆层.该材料组装的半电池在125 mAh·g^-1电流密度下循环175圈后容量达191.1 mAh·g^-1,容量保持率为81.8%,平均每圈电压衰减仅为1.09 mV.磷酸锂包覆层缓解了材料表面与电解液之间的副反应,抑制了不可逆相变和过渡金属溶出,同时磷酸锂作为锂离子导体促进锂离子传输.本工作表明沉淀转化法原位包覆磷酸锂是提升富锂锰基正极材料性能的有效途径.     

光学薄膜测量时平顶光束激励的表面热透镜理论模型

推导了调制的平顶光束激励下基于Fresnel衍射积分的表面热透镜理论，通过数值模拟，比较了平顶光束和高斯光束激励下样品内部温度场、表面形变场和探测光衍射信号的径向分布，分析了影响表面热透镜信号的实验参数.结果表明，在最佳探测位置，平顶光束激励下的表面热透镜系统比相同情况下高斯光束激励下的灵敏度高，最高时约2倍，更有利于薄膜吸收测量. 关键词： 表面热透镜 光学薄膜 平顶光束     

Waterborne crackle decorative coatings and crack patterns

A preparation method of waterborne crackle decorative coatings was reported in this paper and the factors that influence crack patterns were investigated. The crackle coating consisted of a waterborne basecoat and a waterborne topcoat. The basecoat was made from two-component epoxy emulsion and the topcoat was made from fluorine-containing acrylic emulsion, silicone-acrylic emulsion or styrene-acrylic emulsion. Three junction types of crack patterns were prepared by the three top coatings, which were T-junction, Y-junction and mixed junction. T-junction type with long and straight cracks was prepared from styrene-acrylic emulsion 296DS. Y-junction type with curve and short cracks was prepared from fluorine-containing acrylic emulsion A603C and mixed junctions type was made from silicone-acrylic emulsion. Crack patterns with different spacing were prepared by controlling the thickness of topcoat, dryness of basecoat or conditions of film forming. The characterize methods of type and spacing for crack pattern were developed and properties of coating film including adhesion, water resistance, scrub resistance and so on were tested. The results showed that the crackle coatings possessed satisfactory properties for practical application.     

耐高温CrAlON基太阳能光谱选择性吸收涂层的制备与热稳定性

光谱选择性吸收涂层是太阳能光-热利用技术的核心部件,直接决定着整个系统的转换效率,为了提高涂层的选择吸收性和热稳定性,本文提出以金属氮化物替代金属纳米颗粒,构建纳米晶-非晶异质结构的思路,并采用多弧离子镀制备了Cr/CrAlN/CrAlON/CrAlN/CrAlON/CrAlO多吸收层光谱选择性吸收涂层,其吸收率达0....     

氘代聚合物膜靶制备技术与性能研究

 氘代聚合物膜是快点火基础物理实验的一种重要靶型。通过氘代苯乙烯单体的本体自由基聚合反应制备氘代聚苯乙烯，并利用流延法和浇铸法制备出厚度从几十nm到数百μm的膜靶。溶剂挥发过程中的随机扰动对膜厚均匀性造成影响，采用清洁的基片和在涂沫基片或模具外加防护罩可以降低这种影响。采用PVA作脱膜剂有利于获得较薄的聚合物薄膜。DSC分析表明薄膜的玻璃化转变温度与热处理过程有关，缓慢退火有利于提高Ｔ-g和储能模量。