Synthesis and characterization of perfluoro[1-(2-fluorosulfonyl)ethoxy]ethyl end-capped styrene oligomers

Styrene oligomers with perfluoro[1-(2-fluorosulfonyl)ethoxy]ethyl end-groups have been synthesized with moderate to high yields (52-97%) via radical oligomerization by using perfluoro[2-(2-fluorosulfonyl)ethoxy]propyonyl peroxide (PPP) at various reactant ratios of styrene over PPP (80, 160, 240, 300, 360 and 420) and different temperatures (33, 37 and 42 °C), and characterized by FTIR, ¹H NMR and ¹⁹F NMR. The molecular weight of the oligomers measured by gel permeation chromatography (GPC) is dependent on the reactant ratio and reaction temperature. The polydispersity of the oligomers varies from 1.99 to 3.30. The oligomer obtained at the reactant ratio of 300 has the maximum yield (97%) and much broader polydispersity (3.30). The contact angles of water, θ_H2O, on the oligomer films are much bigger than that of polystyrene (PS). The glass transition temperature of the oligomers, T_g, increases with the increase of molecular weight and is lower than that of the parent polymer.     

由聚苯胺粒子组成的电流变液的研究

由经碱处理的掺杂态聚苯胺（ＰＡｎ）制得高介电常数的半导体ＰＡｎ粒子，将其悬浮于电绝缘油可组成电流变液，讨论了电流变（ＥＲ）液的静态屈服应力（τ＿ｓ），电流密度等性能与ＰＡｎ的介电常数（ε＿ｐ），导电率（σ），体积分数和应用电场强度的关系。对导电率相同的ＰＡｎ粒子，用氨水处理的ＰＡｎ粒子ε＿ｐ较用ＮａＯＨ液处理的高，前者在σ足够低如σ≤１．０×１０￣（－７）／ｃｍ时，ＥＲ液的τ＿ｓ随偶极系数的平方（β￣２）的增大而呈现非线性增加；后者ＥＲ液的τ＿ｓ随β￣２的增大出现一最大值．结果表明：由聚苯胺粒子可组成高电流变活性的无水ＥＲ液．     

丙烯酸甲酯/4-丙烯酰胺基-2,2,6,6-四甲基哌啶光共聚合体系的竞聚率和序列分布研究

以丙烯酸甲酯(MA,M1)和4-丙烯酰胺基-2,2,6,6-四甲基哌啶(AATP,M2)溶液光共聚合体系为研究对象,采用1H-NMR手段测定了MA/AATP共聚物的组成,用Mayo-Lewis积分法和扩展Kelen-Tüdos方法计算的竞聚率分别为0.88相似文献   

Total synthesis of crotophorbolone

As a natural diterpenoid, crotophorbolone possesses a challenging trans,trans-5/7/6 framework decorated with six contiguous stereogenic centers and is structurally and biogenetically related to tigliane-type diterpenoids with intriguing bioactivities such as phorbol and prostratin. Based on the convergent strategy, we completed an eighteen-step total synthesis of crotophorbolone starting from (−)-carvone and (+)-dimethyl-2,3-O-isopropylidene-l-tartrate. The key elements of the synthesis involve expedient installation of the six-membered ring and the five-membered ring with multiple functional groups at an early stage, cyclization of the seven-membered ring through alkenylation of the ketone between the five-membered ring and the six-membered ring, functional group-sensitive ring-closing metathesis and final selective introduction of hydroxyls at C₂₀ and C₄.

Convergent total synthesis of crotophorbolone was accomplished in 18 longest linear steps. Observation of unexpected thermodynamic stability of a cis,trans-5/7/6 tricycle would benefit synthetic design of tigliane- and daphnane-related diterpenoids.     

Solvation of acylium fragment ions in electrospray ionization quadrupole ion trap and Fourier transform ion cyclotron resonance mass spectrometry

In electrospray ionization (ESI) quadrupole ion trap and Fourier transform ion cyclotron resonance mass spectrometry, certain fragment ions (e.g. acylium ions) generated either during the ion transportation process (in the source interface region) or in the ion trap are found to undergo ion--molecule reactions with ESI solvent molecules (water, acetonitrile and aliphatic alcohols) to form adduct species. These unexpected solvated fragment ions severely complicate the interpretation of mass spectrometic data. High-resolution accurate mass measurements are important in establishing the elemental compositions of these adduct species and preventing erroneous data interpretation.     

紫荆花红色素开发利用的研究

首次报道紫荆花红色素的提取纯化方法及红色素的理化性质，并与玫瑰茄红色素作对比研究，证实同属于花青甙类化合物，又经急性毒性试验证明其毒性极低，故紫荆花天然红色素具有开发利用的价值。     

应用反向传播神经网络预测化合物脑血分配系数

选用27种三维结构性质描述符对脑血分配系数预测建立神经网络模型.网络模型选用典型的适合函数逼近的两层结构神经网络对脑血分配系数(lgBB,BB为脑血浓度比)进行预测,计算中采用的模型具有一个双曲正切型激活函数的隐含层和一个线性激活函数的输出层.计算表明,使用小心选择的反向传播神经网络模型对化合物脑血分配系数具有较好的预测能力.     

Multilevel structure of sludge flocs

In this work, the structure of two kaolin sludges and a waste activated sludge are investigated using both light-scattering and free-settling methods. Fractal dimensions estimated by the light-scattering and free-settling techniques (D(S) and D(F) respectively) differ significantly and support the hypothesis that naturally occurring aggregates possess a multilevel structure. A two-level floc structural model comprised of (i) a primary floc (of fractal dimension D(S)) consisting of primary particles and (ii) a secondary floc (of fractal dimension D(F)) consisting of the microflocs is proposed to interpret the experimental findings. The structural changes of sludge flocs before and after cationic flocculation are interpreted using the proposed two-level model.     

聚丙烯与SBS嵌段共聚物共混时的结晶行为

用偏光显微镜,小角光散射,动态力学测量和DSC等方法研究了聚丙烯和SBS共混物的结晶行为。结果表明,SBS的混入可以降低聚丙烯的结晶程度和阻碍球晶的形成,因而有利于提高聚丙烯塑料的抗冲击性能。从DSC实验也看到共混物中的聚丙烯具有较高的结晶速率。