Highly Enantioselective Catalytic System for Asymmetric Copolymerization of Carbon Dioxide and Cyclohexene Oxide

A new ligand can be easily prepared, and its intramolecular dinuclear zinc complexes act as a high performance catalyst for the asymmetric alternating copolymerization of cyclohexene oxide and CO₂ under very mild conditions (1 atm CO₂, room temperature), affording completely alternating polycarbonates with up to 93.8 % enantiomeric excess (ee) and 98 % yield. A high M_n value of 28 600 and a relatively narrow polydispersity (M_w/M_n ratio) of 1.43 were also achieved.     

Solvothermal Transformation of a Calcium Oleate Precursor into Large‐Sized Highly Ordered Arrays of Ultralong Hydroxyapatite Microtubes

Hydroxyapatite (HAP), a well‐known member of the calcium phosphate family, is the major inorganic component of bones and teeth in vertebrates. The highly ordered arrays of HAP structures are of great significance for hard tissue repair and for understanding the formation mechanisms of bones and teeth. However, the synthesis of highly ordered HAP structure arrays remains a great challenge. In this work, inspired by the ordered structure of tooth enamel, we have successfully synthesized three‐dimensional bulk materials with large sizes (millimeter scale) that are made of highly ordered arrays of ultralong HAP microtubes (HOAUHMs) by solvothermal transformation of calcium oleate precursor. The core–shell‐structured oblate sphere consists of a core that is composed of HAP nanorods and a shell that consists of highly ordered HAP microtube arrays. The prepared HOAUHMs are large: 6.0 mm in diameter and up to 1.4 mm in thickness. With increasing solvothermal reaction time, the HOAUHMs grow larger; the microtubes become more uniform and more ordered. This work provides a new synthetic method for synthesizing highly ordered arrays of uniform HAP ultralong microtubes that are promising for biomedical applications.     

Highly Flexible and Nonflammable Inorganic Hydroxyapatite Paper

A highly flexible and nonflammable inorganic hydroxyapatite (HAP) paper made from HAP ultralong nanowires is reported. The paper can be used for printing and writing and is promising for the permanent and safe storage of information, such as archives and important documents. The HAP paper is also an excellent and recyclable adsorbent for organic pollutants.     

Coloring properties of novel 1,4-distyrylbenzene and 4,4′-distyrylbiphenyl fluorescent brighteners and their arrangement in cotton and polyester fiber

Some novel 1,4-distyrylbenzene (DSB) and 4,4′-distyrylbiphenyl (DSBP) fluorescent brighteners (FBs) were used to dye polyester and cotton fabrics. The CIE whiteness, color hue and reflectance spectrum of dyed fabrics were compared. DSBP derivatives could dye the cotton and polyester fabrics with a higher whiteness level and had a lower fluorescent quenching concentration than DSB derivatives. The color hue for the fabric dyed with DSB FBs was yellow-green, whereas that dyed with DSBP was blue–violet. The molecular arrangement in the fiber had a significant influence on their optical properties, resulting in different coloring properties. The increase in molecule planarity and rigidity generated by the interaction between the polymer and FB molecules caused a remarkable bathochromic shift in emission and excitation spectra. The H-aggregate of the DSB molecule in the fiber was easily generated, and the degree of aggregation increased with the molecular polarity. However, the aggregation of DSBP molecules in the polyester and cotton fiber was not found. The surface region of the cotton fiber was filled with FB molecules, whereas FB molecules in the polyester fiber aggregated easily, and incident light could pass through the surface region.     

Effects of lignin and hemicellulose contents on dissolution of wood pulp in aqueous NaOH/urea solution

Four species of delignified woodchips with about 1 % lignin content (Chlorite–Woodchips) and a series of softwood pulps with different lignin contents were prepared by sodium chlorite delignification. After mechanical defibration, some Chlorite–Woodchips were directly subjected to dissolution treatment in NaOH/urea solvent; the others were first treated with NaOH solution to remove the hemicellulose to obtain NaOH–Chlorite–Woodchips or oxidized with potassium permanganate (OPP) to remove lignin completely to obtain OPP–Chlorite–Woodchips, and then subjected to the dissolution in NaOH/urea solvent. The results showed that the dissolved proportion of the Chlorite–Woodchips ranged from 36 to 46 %, the dissolved proportion of glucan was within 12 %, and most of the hemicellulose was dissolved in NaOH/urea solvent. Compared with Chlorite–Woodchips, the dissolved proportion of NaOH–Chlorite–Woodchips was lower, but their dissolved proportion of glucan was higher. After further permanganate delignification, both the dissolved proportion of the OPP–Chlorite–Woodchips and the dissolved proportion of glucan of the OPP–Chlorite–Woodchips were higher than those of the Chlorite–Woodchips. However, the dissolved proportion of glucan was still limited to only 15–30 %. The effect of the lignin content of softwood pulps on their dissolution is complicated. With the decrease of the lignin content of softwood pulp from 6.9 to 2.8 %, the dissolved proportion of pulp increased from 14 to 26 %. However, further reduction of lignin content from 2.8 to 0.3 % led to a decrease in the dissolved proportion of pulp from 26 to 12 %. The dissolved proportion of glucan followed the same tendency. These results indicated that the dissolution of wood cellulose in NaOH/urea solvent is not simply controlled by the hemicellulose and lignin contents, but also by some other factors.     

室温合成二硫化二正丁基黄原酸酯及其表征

以正丁醇、氢氧化钠和二硫化碳为原料,水作溶剂合成正丁基黄原酸钠,再与一氯化硫反应,室温条件下合成对称的二硫化二正丁基黄原酸酯,并探讨了反应条件对合成正丁基黄原酸钠和二硫化二正丁基黄原酸酯产率的影响。通过红外(FT-IR)、核磁(1H NMR)、质谱(MS)及元素分析等技术手段确定了产物的结构。优化的合成条件为:n(正丁基黄原酸钠)∶n(S2Cl2)=2∶1.1,温度为室温,溶剂为THF,反应时间为2 min,产率可达83.2%,反应条件温和,反应迅速、收率高。     

Thermoresponsive hybrid hydrogel of oxidized nanocellulose using a polypeptide crosslinker

Thermoresponsive hybrid nanocellulose hydrogels were prepared from a mixture of oxidized nanocellulose and elastin-like polypeptide (ELP). Positively charged ELP was used as a polymeric crosslinker for conjugation with negatively charged nanocellulose. Hydrogel formation was triggered by a simple increase in temperature, and the hydrogel was reversibly returned to the liquid phase by decreasing temperature. Surface potential measurement confirmed the electrostatic properties of oxidized nanocellulose and ELP molecules. The surface morphology of hydrogels was observed by atomic force microscopy and field emission-scanning electron microscopy. Conformational changes in the ELP/nanocellulose hybrid were characterized by circular dichroism. The ELP/nanocellulose hybrid hydrogel was noncytotoxic and suitable for encapsulating cells, indicating its potential for biomedical applications.     

液相色谱/串联质谱法测定水中邻苯二甲酸酯类化合物

建立了直接进样-超高效液相色谱/三重四极杆串联质谱法同时测定水中6种邻苯二甲酸酯类化合物的方法。水样经离心后取上清液进样,采用BEH C18柱,以水(0.1%甲酸)-乙腈作为流动相进行梯度洗脱,采用串联质谱进行检测。实验通过在液相色谱系统中装入一根吸附分配柱,很好地解决了液相色谱系统的干扰问题。6种邻苯二甲酸酯类在一定范围内线性良好(r=0.9990~0.9996),回收率为84.3%~102%,相对标准偏差为1.0%~8.7%,方法检出限为0.05~0.5μg/L。方法适用于测定地表水中6种邻苯二甲酸酯类化合物的残留。     

(P^N^P)钴配合物/倍半氯化乙基铝催化苯乙烯聚合的研究

采用含氮双膦配体与无水氯化钴反应可制得一系列相应的(P^N^P)钴配合物,并研究了该系列钴配合物对苯乙烯聚合的催化性能.在助催化剂倍半氯化乙基铝(EASC)的活化下,该系列钴配合物对甲苯中的苯乙烯溶液聚合表现出高的催化活性(可达5.44×105g(PS)·mol-1(Co)·h-1).通过对不同苯乙烯单体用量、助催化剂用量(Al/Co摩尔比)、聚合温度以及催化剂的配体环境等的研究,详细考察了这些因素对聚合反应和聚合产物性能的影响.通过凝胶渗透色谱法(GPC)和核磁共振碳谱(13C-NMR)表征了所得聚合产物的分子量及分子量分布和微观结构,分析结果表明,所得聚苯乙烯具有较低的分子量(Mn=2000~5900)和较窄的分子量分布(1.75~2.05),其微观结构是无规的.     

Lithiation of a Silyl Ether: Formation of an ortho‐Fries Hydroxyketone

A hydroxy‐directed alkylation of an N,N‐diethylarylamide using CIPE‐assisted α‐silyl carbanions (CIPE=complex‐induced proximity effect) has been developed using a simple reagent combination of LDA (lithium diisopropylamide) and chlorosilane. A study of the mechanism, and the application of the procedure to an anionic Snieckus–Fries rearrangement for a highly efficient synthesis of the potent phosphatidylinositol 3‐kinase (PI3K) inhibitor LY294002, are reported.