F127稳固Pd纳米粒子催化剂催化油酸甲酯加氢反应的研究

制备了F_(127)稳固Pd纳米粒子催化剂(Pd/F_(127)),并将其用于油酸甲酯加氢制备C_(18)醇的反应。结果表明:F_(127)稳固Pd纳米粒子催化体系对油酸甲酯加氢反应具有催化活性高、稳定性好、易与产物分离、可循环利用等特性;在油酸甲酯用量3.0 g、Pd质量分数0.36%的Pd/F_(127)催化体系用量6.0 g(m(Pd)∶m(F_(127))=1∶25)、反应温度230℃、氢气压力6 MPa、反应时间8 h的较佳实验条件下,产物羟值(KOH)和碘值(I)分别为173.3 mg/g、10.5 g/100 g;Pd/F_(127)分散均匀,Pd纳米粒子平均粒径2.36 nm;分离所得稳固Pd纳米粒子催化体系不经任何处理重复使用5次后,仍有较好的催化活性。     

尿素包合法从葡萄籽油中富集高纯度亚油酸甲酯及包合物表征分析

为提升葡萄籽的使用价值,以葡萄籽油为原料,采用尿素包合法富集高纯度亚油酸甲酯。研究了脂肪酸甲酯与尿素质量比、尿素与95%乙醇质量比、包合时间和包合温度对包合效果的影响,并采用傅里叶变换红外光谱(FTIR)、X射线衍射(XRD)和扫描电子显微镜(SEM)对空白尿素结晶物和包合固形物进行表征。结果表明:制备高纯度亚油酸甲酯的最佳工艺条件为脂肪酸甲酯与尿素质量比1∶2、尿素与95%乙醇质量比1∶4、包合温度5℃、包合时间10 h,在此条件下得到的亚油酸甲酯含量为94.83%,收率为40.41%;FTIR和XRD分析表明,尿素包合反应没有新的官能团生成,且脂肪酸甲酯的包合降低了尿素的结晶度;SEM图像显示,尿素与脂肪酸甲酯形成了六棱体包合物。综上,尿素包合法为富集葡萄籽油中的高纯度亚油酸甲酯的有效方法。     

二叔丁基氮氧自由基对AN_MA和MMA的高效阻聚作用

用混浊法和沸腾法分别研究了二叔丁基氮氧自由基(DTBNO)对丙烯腈(AN)及丙烯酸甲酯(MA)、甲基丙烯酸甲酯(MMA)自由基聚合的阻聚作用。结果表明,DTBNO对AN有较强的阻聚作用;DTBNO与对苯二酚(HQ)、苯醌(BQ)、二乙基羟胺(DEHA)等分别组成二元混合物时,其阻聚效果非常明显。当DTBNO-DEHA和DtBNO-HQ的浓度(ppm,下同)比分别为500:1000和1000:500时,对AN的阻聚效果最好;在二元混合阻聚剂中加入适量吩噻嗪(PT),其阻聚效果更佳,如DTBNO-DEHA-PT(500:500:500)在100℃时可使MMA完全终止聚合反应。     

Influence of free volume fraction,inter/intramolecular energy ratio,and chain segment density on the Gibbs-DiMarzio theory of the glass transition

Based upon computer analysis, the Gibbs-DiMarzio (G-DM) theory is evaluated for the case of (a) constant V₀ and (b) constant r where V₀ is the fractional free volume at T_g and r is the ratio of the hole (E₀) to the flex (ε) energy. For each respective case, results are presented in a reduced variables format that indicate the extent to which r and V₀ vary at the transition temperature as a function of the reciprocal degree of polymerization (P^?1). To further account for chemical differences that exist among polymers, an index (n) is introduced that ultimately incorporates the effective number average of chain atom segments (x?) per P?. Using these reduced variables plots, the effects of V₀, r, and n are compared with the T_g data for four well-documented polymers. Although the theory adequately describes the PMMA, PS, and PVC data, for PαMS the fit is doubtful. The analysis demonstrates that, in order to maintain V₀ within the range of 0.015–0.045, r must remain within approximately 1.0–1.1. Moreover, under conditions of either constant V₀ or r, other more flexible polymers require that $\text{n?10}$.     

Wound-induced changes in root and shoot jasmonic acid pools correlate with induced nicotine synthesis inNicotiana sylvestris spegazzini and comes

Leaf damage by herbivores inNicotiana sylvestris Spegazzini and Comes (Solanaceae) produces a damage signal that dramatically increasesde novo nicotine synthesis in the roots. The increased synthesis leads to increases in whole-plant nicotine pools, which in turn make plants more resistant to further herbivore attack. Because signal production and the response to the signal occur in widely separated tissues, the speed with which different damage signals exit a damaged leaf can be studied. We propose that electrical damage signals should exit a leaf faster (less than 60 min) than chemical damage signals. Excision of a leaf induces a smaller increase in nicotine production than does puncture damage, so we examined our proposition by excising previously punctured leaves at 1, 60, and 960 min after leaf puncture and quantifying the induced whole-plant nicotine pools six days later when the induced nicotine production had reached a maximum. Significant induced nicotine production occurred only if punctured leaves were excised more than 1 hr after puncture, which is consistent with the characteristics of a slow-moving chemical signal rather than a fast-moving electrical signal. We explore the nature of the chemical signal and demonstrate that additions of 90µg or more of methyl jasmonate (MJ) in an aqueous solution to the roots of hydroponically grown plants inducede novo nicotine synthesis from¹⁵NO₃ in a manner similar to that induced by leaf damage. We examine the hypothesis that jasmonic acid (JA) functions in the transfer of the damage signal from shoot to root. Using GC-MS techniques to quantify whole-plant JA pools, we demonstrate that leaf damage rapidly (<0.5 hr) increases shoot JA pools and, more slowly (<2 hr), root JA pools. JA levels subsequently decay to levels found in undamaged plants within 24 hr and 10 hr for shoots and roots, respectively. The addition of sufficient quantities (186µg) of MJ in a lanolin paste to leaves from hydroponically grown plants significantly increased endogenous root JA pools and increasedde novo nicotine synthesis in these plants. However, the addition of 93µg or less of MJ did not significantly increase endogenous root JA pools and did not significantly affectde novo nicotine synthesis. We propose that wounding increases shoot JA pools, which either directly through transport or indirectly through a systemin-like signal increase root JA pools, which, in turn, stimulate root nicotine synthesis and increase whole-plant nicotine pools.     

Li^＋掺杂纳米TiO2的制备及其光催化性能研究

采用溶胶-凝胶法和浸渍法制备了Li^＋掺杂纳米TiO2光催化剂，并用XRD和TEM等技术进行了表征；用pH值漂移法测量了催化剂的零电位pH值（pHPZC）．结果表明，500℃煅烧制得的催化剂均为锐钛矿相；Li^＋的掺杂抑制了TiO2，粒子的生长，提高了催化剂的分散性；催化剂的零电位pH值为6．6—8．1，其值取决于Li^＋的浓度和掺杂方式．分别以紫外光和太阳光为光源，孔雀石绿和甲基橙为降解物评价了催化剂的光催化活性；并用气相色谱测试了污染物降解产生的CO2的含量．结果显示，对孔雀石绿的降解，浸渍法和溶胶-凝胶法掺Li^＋都能有效提高TiO2的光催化活性，但浸渍法比溶胶-凝胶法效果更好，催化活性最高的为浸渍法制备的5％（摩尔分数）Li^＋掺杂TiO2，其在紫外光和太阳光下的光催化活性分别比纯TiO2提高了6—8倍和9-10倍；对甲基橙的降解，除溶胶-凝胶法制备的3％（摩尔分数）Li^＋掺杂TiO2能稍提高光催化活性外，其它Li＇的掺杂都不同程度降低了TiO2的光催化活性；随污染物降解率的增加，最终降解产物CO2的含量增加．实验结果表明，Li^＋掺杂改变了催化剂表面的电荷状态从而改变了催化剂的零电位pH值是造成催化剂降解不同污染物具有不同催化活性的主要原因．     

Natural rubber‐g‐methyl methacrylate/poly(methyl methacrylate) blends

The grafting of the methyl methacrylate (MMA) monomer onto natural rubber using potassium persulfate as an initiator was carried out by emulsion polymerization. The rubber macroradicals reacted with MMA to form graft copolymers. The morphology of grafted natural rubber (GNR) was determined by transmission electron microscopy and it was confirmed that the graft copolymerization was a surface‐controlled process. The effects of the initiator concentration, reaction temperature, monomer concentration, and reaction time on the monomer conversion and grafting efficiency were investigated. The grafting efficiency of the GNR was determined by a solvent‐extraction technique. The natural rubber‐g‐methyl methacrylate/poly(methyl methacrylate) (NR‐g‐MMA/PMMA) blends were prepared by a melt‐mixing system. The mechanical properties and the fracture behavior of GNR/PMMA blends were evaluated as a function of the graft copolymer composition and the blend ratio. The tensile strength, tear strength, and hardness increased with an increase in PMMA content. The tensile fracture surface examined by scanning electron microscopy disclosed that the graft copolymer acted as an interfacial agent and gave a good adhesion between the two phases of the compatibilized blend. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 428–439, 2001     

油酸甲酯乙氧基化物磺酸盐的合成与性能研究

以油酸甲酯乙氧基化物(OMEE)为原料,通过与亚硫酸氢钠一步法加成磺化得到油酸甲酯乙氧基化物磺酸盐(OMEES),并通过皂化值、碘值、阴离子含量的测定以及红外光谱确定合成的产物结构。对OMEES和OMEE进行平衡表面张力、动态表面张力、动态接触角以及主要应用性能的测试。结果表明:对于OMEES,γ_(cmc)=36.3 mN/m,吸附速率较慢,吸附量较少,并且随着表面活性剂浓度的增大铺展润湿性能逐渐增强。磺酸基的引入增加了原料的亲水性,使其起泡能力有所增强。     

有机硅封闭剂及其性能的研究

研究了由甲基三乙氧基硅烷等有机硅氧烷单体,通过缩聚反应,制得甲基硅树脂;并以此为原料加入固化促进剂和偶联剂配制成一种应用于金属电镀后表面封闭处理的封闭剂溶液。另外还研究了固化条件对封闭剂涂层性能的影响。     

Chiral Discrimination Mechanisms by Silylated-Acetylated Cyclodextrins: Superficial Interactions vs. Inclusion

Cyclodextrin derivatives constitute a powerful class of auxiliary agents for the discrimination of apolar chiral substrates. Both host–guest inclusion phenomena and interactions with the derivatizing groups located on the surface of the macrocycle could drive the enantiodiscrimination; thus, it is important to understand the role that these processes play in the rational design of new chiral selectors. The purpose of this study is to compare via nuclear magnetic resonance (NMR) spectroscopy the efficiency of silylated-acetylated α-, β-, and γ-cyclodextrins in the chiral discrimination of 1,1,1,3,3-pentafluoro-2-(fluoromethoxy)-3-methoxypropane (compound B) and methyl 2-chloropropionate (MCP). NMR DOSY (Diffusion Ordered SpectroscopY) experiments were conducted for the determination of the bound molar fractions and the association constants, whereas ROESY (Rotating-frame Overhauser Enhancement SpectroscopY) measurements provided information on the hosts’ conformation and on the interaction phenomena with the guests. Compound B, endowed with fluorinated moieties, is not deeply included due to attractive Si-F interactions occurring at the external surface of the cyclodextrins. Therefore, a low selectivity toward the size of cyclodextrin cavity is found. By contrast, enantiodiscrimination of MCP relies on the optimal fitting between the size of the guest and that of the cyclodextrin cavity.