纤维素醋酸酯的均相合成

纤维素的非均相反应取代不均匀、产率低。本文用纤维素在LiCl／DMAc溶液中的均相反应。制得了纤维素三醋酸酯(CTA)、纤维素二醋酸酯(CDA)、纤维素—醋酸酯(CMA),并对产品结构性能进行了表征。     

Synthesis of Mesoporous Cu-Mn-Al_2O_3 Materials and Their Applications to Preferential Catalytic Oxidation of CO in a Hydrogen-rich Stream

A series of mesoporous Cu-Mn-Al2O3(CMA) materials was synthesized at moderate temperature and their structures were characterized by XRD, N2 physical adsorption and TPR techniques. It was found that using metal complex ion[Cu(NH3) 42+-Mn(NH3)62+] as raw materials is easier to form good-structure mesoporous Cu-Mn-Al2O3 materials than using its nitrate salt [Cu(NO3)2-Mn(NO3)2]. The TPR tests results indicate that CuO and MnOx were homogeneously dispersed in the mesoporous materials. Their catalytic application to preferential catalytic oxidation of CO in a hydrogen-rich stream was studied. The activity varies in the order of CMA(1:1, molar ratio) CMA(1:2)CMA(2:1)CMA(CP)CMA(1:0)≈CMA(0:1). The CMA(1:0) and CMA(0:1) have lower activity compared to other samples, implying that there existed coordination effect between Cu-Mn in the samples. The selectivity varied in the order of CMA(0:1)≥CMA(1:2)CMA(1:1)CMA(2:1)CMA(1:0) at higher temperature (≥120 °C), indicating that increasing the Cu content enhanced the conversion of H2. The sample CMA(CP) made by coprecipitation method has a lower CO oxidation activity and selectivity than its counter-parts of mesoporous Cu-Mn-Al2O3 materials[CMA(1:2)], this attributed to the lower surface area of the former and poor interaction of CuO with MnOx.     

利用盐泥制备醋酸钙镁融雪剂

以固废盐泥为主要原料,通过与冰醋酸反应制备了醋酸钙镁(CMA)融雪剂,通过热重-示差扫描量热(TG-DSC)和X射线衍射(XRD)对CMA样品进行了分析。依据国家标准"GB/T 23851-2009"对制备的CMA产品进行相关性能参数的测定,融雪化冰能力、pH和碳钢腐蚀率等指标均能满足要求,该方法为工业化生产低成本CMA融雪剂提供理论依据。     

电子能谱仪中筒镜分析器及其相关部件的维修

筒镜分析器(CMA)是俄歇电子能谱(AES)装置或AES同X射线光电子能谱(XPS或称ESCA)联合装置的关键部件。本文以ESCA/SAM550电子能谱仪中由于CMA故障,造成仪器没有AES和ESCA信号响应为例,介绍一种基本故障分析方法以及CMA和同轴电子枪等部件的维修保养经验。     

软质聚氨酯泡沫塑料用无卤阻燃剂的研究

本文以羟基苯氧膦丙烯酸(CEPP)和三聚氰胺(MA)为原料合成了一种含磷、氮无卤阻燃剂(CMA),采用FT-IR表征了阻燃剂的化学结构,并将该阻燃剂用于软质聚氨酯泡沫(FPUF)的阻燃。用扫描电镜(SEM)研究了阻燃剂的加入对FPUF的形态的影响,通过LO I和垂直燃烧(Cal.117A)测试研究了该阻燃剂对FPUF的阻燃效果。结果表明,CMA可以有效提高FPUF的阻燃性:当CMA的添加量为10%时,FPUF即可通过Cal.117A测试,其LO I值也从17.3提高到23.0;随阻燃剂添加量的增加,FPUF的阻燃性能也逐渐提高。TG测试结果表明CMA的加入对FPUF的热稳定性没有多大影响。     

取代二苯醚的新合成反应及历程研究

在碱金属亚硝酸盐和碳酸盐存在下,被强吸电子基团取代的硝基苯在非质子极性溶剂中能发生自身缩合反应,生成结构对称的双取代二苯醚,收率较高。此类反应的主要历程属于S_NA_r,但同时也存在着S_(RN)A_r(SET)历程作为次要途径。     

芳香取代的几种新方法

本文介绍了芳香取代的几种新方法及其在有机合成中的应用。主要包括：（１）Ｖｉｃａｒｉｏｕｓ亲核取代，（２）邻位金属化定向反应，（３）钯催化的取代方法等。     

新型多甲氧基取代二苯醚类化合物的合成

以碘化亚铜为催化剂,Cs2CO3为碱,甲氧基取代苯酚(1)和甲氧基取代碘苯通过偶联反应形成C-O-C键,合成了27个新型的多甲氧基取代二苯醚类化合物,其结构经1H NMR和IR表征。最佳合成条件为:1 1.0mmol,CuI 0.10 mmol,Cs2CO32.0 mmol,DMF为溶剂,N2保护下于130℃下回流反应16 h。在最佳反应条件下,收率37%~94%。     

芳香取代反应—ipso取代反应

谈到芳香取代反应,人们立刻会想到芳环上取代基的o~-、p-、m~-位上氢原子的取代反应。然而对另一类反应,即环上取代基本身的取代反应却少为人知。它是起始于试剂对芳环上取代基所在位置(ipso位)的进攻,进而置换了该取代基的反应。称作ipso取代反应。某些研究表明,试剂对氢原子所在位置的进攻与它对ipso位的进攻处于竞争状态,往     

自由基化学

近２０年来,中国的自由基化学研究在若干领域取得了重要的进展,包括单电子转移反应自旋离域取代基参数的建立,自由基的热力学稳定性研究等。哌啶氮氧自由基与一些生物小分子,如半膛氨酸、谷胱甘肽、抗不血酸等,在溶液及胶束中的反应经过动力学研究证明反庆的单电子转移机理。哌啶氧铵盐氧化芳香胺和含氮硫芳杂环为相应的自由基正离子,首次报道了噻茵及甲基吩噻唪自由基正离子与其中性母体之间电子转移的同位素效应。难过对对位     

在苯-乙醇介质中生成的羧甲基纤维素取代基分布的研究

以三组份两相液体苯 乙醇 水为介质合成羧甲基纤维素（ＣＭＣ），应用１Ｈ ＮＭＲ谱图分析了ＣＭＣ中羧甲基在葡萄糖单元（ＡＧＵ）的Ｃ２、Ｃ３及Ｃ６位上对羟基的取代分布．结果表明，取代基的分布顺序是Ｃ６＞Ｃ２＞Ｃ３；当取代度（ＤＳ）低于１０时，Ｃ２∶Ｃ３∶Ｃ６近似于１４５∶１∶２１５；ＤＳ高于１０以后，分布趋于相同，通过对ＣＭＣ的Ｘ 衍射分析解释了取代基分布规律．同时研究了苯的影响，证实相同取代度下，在苯 乙醇 水中生成的ＣＭＣ试样，其Ｃ６位取代基分布多于在乙醇 水中生成的试样．     

Benzylation of cellulose in the solvent dimethylsulfoxide/tetrabutylammonium fluoride trihydrate

The cellulose solvent dimethylsulfoxide/tetrabutylammonium fluoride trihydrate (TBAF·3 H₂O) was studied as reaction medium for the synthesis of benzyl cellulose (BC) by treating the dissolved polymer with benzyl chloride in the presence of solid NaOH or aqueous NaOH solution. BC samples with degree of substitution (DS) between 0.40 and 2.85 were accessible applying different molar ratios. The studies show that both the TBAF·3 H₂O concentration and the molar ratio of the reagents to repeating unit influence the DS. The solubility of the BC synthesized in a different way, however, of comparable DS is different. Structural analyses were carried out by means of FTIR-, ¹H- and ¹³C NMR spectroscopy. SEC measurements revealed polymer aggregation in samples of low DS synthesized in a solvent containing 9.0% TBAF·3 H₂O. At higher concentration of TBAF·3 H₂O in the solvent, the BC samples obtained do not form aggregates. BC of high DS is crystalline and shows thermotropic liquid crystalline behavior as analyzed by means of DSC. Melting point and degradation temperature are not related to the DS.     

Synthesis and characterization of cellulose derivatives prepared in NaOH/urea aqueous solutions

We successfully synthesized hydroxypropylcellulose (HPC) and methylcellulose (MC) in high yields from cellulose in 6 wt % NaOH/4 wt % urea aqueous solutions at 25 °C. The cellulose derivatives were characterized with NMR, size exclusion chromatography/laser light scattering, gas chromatography (GC), ultraviolet, and solubility measurements in different solvents. According to the results of solution ¹³C NMR and GC, the individual degree of substitution (DS; i.e., the average number of substituted hydroxyl groups in the monomer unit) at C‐2 hydroxyl groups was slightly higher than the DS values at C‐3 and C‐6 hydroxyl groups for HPC and MC. In comparison with traditional systems, NaOH/urea aqueous solutions were proved to be a stable and more homogeneous reaction medium for preparing cellulose ether with a more uniform microstructure. The low limits for the average number of moles of the substituent groups per monomer unit and the DS value of water‐soluble HPC were 1.03 and 0.85, respectively. MC (DS = 1.48) had good solubility in both water and organic solvents, and the precipitation point occurred at about 67 °C for a 2% (w/v) aqueous solution. In this way, we could provide a simple, pollution‐free, and homogeneous aqueous solution system for synthesizing cellulose ethers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5911–5920, 2004     

High Substitution Synthesis of Carboxymethyl Chitosan for Properties Improvement of Carboxymethyl Chitosan Films Depending on Particle Sizes

This study investigated the effect of chitosan particle sizes on the properties of carboxymethyl chitosan (CMCh) powders and films. Chitosan powders with different particle sizes (75, 125, 250, 450 and 850 µm) were used to synthesize the CMCh powders. The yield, degree of substitution (DS), and water solubility of the CMCh powders were then determined. The CMCh films prepared with CMCh based on chitosan with different particle sizes were fabricated by a solution casting technique. The water solubility, mechanical properties, and water vapor transmission rate (WVTR) of the CMCh films were measured. As the chitosan particle size decreased, the yield, DS, and water solubility of the synthesized CMCh powders increased. The increase in water solubility was due to an increase in the polarity of the CMCh powder, from a higher conversion of chitosan into CMCh. In addition, the higher conversion of chitosan was also related to a higher surface area in the substitution reaction provided by chitosan powder with a smaller particle size. As the particle size of chitosan decreased, the tensile strength, elongation at break, and WVTR of the CMCh films increased. This study demonstrated that a greater improvement in water solubility of the CMCh powders and films can be achieved by using chitosan powder with a smaller size.     

高直链淀粉乙酸酯的均相合成及其静电纺丝

离子液体1-烯丙基-3-甲基咪唑氯盐(amimCl)可以有效地溶解高直链淀粉.以amimCl为均相反应介质,在无外加催化剂的存在下一步合成了取代度范围较宽的高直链淀粉乙酸酯.考察了反应时间和酰化试剂用量对酰化程度的影响.不同取代度的酰化淀粉在水、丙酮和DMAc等溶剂中表现出不同的溶解性.进一步对高直链淀粉乙酸酯溶液进行静电纺丝,制备出了由直径在数十至数百纳米、表面光滑、连续的纳米纤维组成的超细纤维多孔膜.     

Synthesis and properties of O‐2‐[2‐(2‐methoxyethoxy)ethoxy]acetyl cellulose

In this article, a series of O‐2‐[2‐(2‐methoxyethoxy)ethoxy]acetyl celluloses with different degree of substitution (DS) values was synthesized by a homogeneous reaction of cellulose with 2‐[2‐(2‐methoxyethoxy)ethoxy]acetyl chloride in a 10% (w/w) dimethylacetamide/lithium chloride solution, combined with pyridine as the acid acceptor. The total DS values of the derivatives in anhydroglucose units was determined by ¹H and ¹³C NMR spectra, and ranged from 0.4 to 3.0, depending on the amount of acid chloride in the reaction. The effects of the total DS values and the O‐2‐[2‐(2‐methoxyethoxy)ethoxy]acetyl substituent distribution on the solubility of the derivatives were investigated. The lowest limit of the DS value for water‐soluble O‐2‐[2‐(2‐methoxyethoxy)ethoxy]acetyl cellulose was approximately 0.5, which is lower than that of methylcellulose. The amphiphilic derivatives with higher DS values than 1.7 exhibited a good solubility in both water and organic solvents, such as dimethyl sulfoxide, tetrahydrofuran, and chloroform. Sol‐gel transition in aqueous solution was observed for the amphiphilic derivatives with a higher DS value than 1.7; the precipitation temperature (T_p) decreased as the DS value increased, showing that the derivatives are highly temperature sensitive. The thermal properties of the fully substituted derivative were measured using polarized microscopy, DSC, and X‐ray diffraction; and are discussed in terms of phase transition of the sample derivatives. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 376–382, 2001     

Super-helix formation induced by cyanine J-aggregates onto random-coil carboxymethyl amylose as template

The J-aggregation of Cyanine-1dye in the presence of carboxymethyl amylose (CMA) is described. The J-aggregation requires a large excess CMA concentration; the J-band maximum appears in the concentration range, [CMA]/[dye] = 10-50, depending on the degree of substitution (DS) of carboxylation, where [CMA] is the concentration of polymer repeat units. An extraordinarily large induced circular dichroism (CD) is observed from J-aggregates of the achiral cyanine dye in association with a random coil CMA, suggesting that the CMA is transformed into a helix. The magnitude of CD intensity increases with increasing DS of CMA and pH up to neutral (where a maximum J-aggregation occurs), while the CMA-bound dye monomer and H-aggregates (occurring at pH > or = 9) exhibit no induced CD. The trend in the CD intensity (of the J-aggregates) is in parallel with the fluorescence intensity of the J-aggregates. This suggests that binding of the J-aggregates onto the template CMA is sterically controlled by the asymmetric environment of glucose residues (of CMA) so that more twisting power is exerted with increasing DS (of CMA), rendering the cyanine dye/CMA complex a more rigid (a high fluorescence intensity) super-helix. This is also revealed by the AFM image of a long strand.     

Synthesis and properties of sulfonated polyimides from homologous sulfonated diamines bearing bis(aminophenoxyphenyl)sulfone

Three homologous sulfonated diamines bearing a bis(aminophenoxyphenyl)sulfone structure, namely, bis[4‐(4‐aminophenoxy)phenyl]sulfone‐3,3′‐disulfonic acid (pBAPPS‐3DS), bis[4‐(4‐aminophenoxy)phenyl]sulfone‐2,2′‐disulfonic acid (pBAPPS‐2DS), and bis[4‐(4‐aminophenoxy)‐2‐(3‐sulfobenzoyl)phenyl]sulfone (pBAPPS‐2DSB), were synthesized. A series of sulfonated polyimides (SPIs) were synthesized from 1,4,5,8‐naphthalene tetracarboxylic dianhydride, these sulfonated diamines, and nonsulfonated diamines, and their properties were investigated in comparison with those reported for the SPIs from another homologous diamine or bis[4‐(3‐aminophenoxy)phenyl]sulfone‐3,3′‐disulfonic acid (mBAPPS‐3DS). These SPIs were soluble in common aprotic solvents and showed reasonably high proton conductivity, except for pBAPPS‐2DS‐based SPIs, the conductivity of which was slightly lower because of the lower water uptake. The water stability of these SPIs considerably depended on the structure of the sulfonated diamines and was in the order of pBAPPS‐2DSB ≈ pBAPPS‐2DS > pBAPPS‐3DS ? mBAPPS‐3DS. Their water stability was much lower than that of the SPIs from 4,4′‐bis(4‐aminophenoxy)biphenyl‐3,3′‐disulfonic acid. The reason was discussed on the basis of the basicity of the sulfonated diamine and the solubility property of the SPIs. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2797–2811, 2007     

Structure and solution properties of cyanoethyl celluloses synthesized in LiOH/urea aqueous solution

Cyanoethyl celluloses (CECs) with different degree of substitution (DS) were synthesized by homogeneous reaction of cellulose (cotton linter pulp and absorbent cotton) with acrylonitrile (AN) in LiOH/urea aqueous solutions. The reaction showed quick reactivity and high transfer efficiency of etherification agent. The DS values of CECs were controlled by varying the molar ratio of AN to anhydroglucose unit (AGU) and the cellulose concentration. The DS values of the CEC-1–CEC-10 increased from 0.27 to 1.78 with increasing molar ratio of AN to AGU from 0.5:1 to 9:1. While the CEC-11–CEC-21 with DS values of 0.26–1.81 could be obtained by adjusting the molar ratio from 1:1 to 27:1. The relative reactivity of hydroxyl groups is in the order of C-6 > C-2 > C-3. The DS values of the water-soluble derivatives are in the range of 0.47–1.01. As the DS values increase to 1.37, CEC samples can not be dissolved in water or dilute alkali solution, but have good solubility in organic solvents, such as DMSO, DMF and pyridine. The dilute solution properties and molecular parameters of the CEC samples were studied by static light scattering and dynamic light scattering. The results indicated that the water-soluble samples could form a small number of aggregates spontaneously in 0.9 wt% NaCl aqueous solution, while the water-insoluble samples showed extended stiff chains in 0.5% LiCl–DMAc.     

纤维素在离子液体中的均相乙酰化及其选择性

在1-烯丙基-3-甲基咪唑氯盐(AMIMCl)离子液体中进行了纤维素的均相乙酰化. 酯化剂为乙酸酐和乙酰氯以及加入或不加入催化剂吡啶. 用滴定法确定了产物的取代度(DS), 根据¹³C NMR考察了产物的取代度分布. 结果表明: 酰氯酰化的反应速度比酸酐快; 吡啶能加快乙酸酐的酯化反应, 但减慢酰氯的反应; 使用乙酸酐/吡啶酯化时所得产物具有特殊的取代度分布, 即DS_C-2>> DS _C-3.