Control of mesoporous structure of aerogels derived from cresol-formaldehyde

Polycondensation of a cresol mixture (C(m)) with formaldehyde (F) in basic aqueous solutions leads to formation of highly cross-linked C(m)F aquagels that can be supercritically dried with carbon dioxide to form organic C(m)F aerogels. Aerogels synthesized with different catalyst contents and reactant concentrations are characterized by low-temperature nitrogen adsorption. The present experimental results suggest that the C(m)F aerogels are typical mesoporous materials and have almost no micropores in bulk. The microstructure of the organic C(m)F aerogels can be controlled and tailored effectively by varying synthesis conditions during the initial sol-gel process. C(m)F organic aerogels with specific surface area as high as 627 m(2)/g and corresponding pore volume 2.06 ml/g have been obtained with a dominant pore size of 30 nm. C(m)F organic aerogels with peaky pore size distributions concentrated at 11 nm have also been prepared.     

The theoretical basis of column chromatography in multicomponent separations. Part 2: Peak capacity. Column systems with good selectivity

The selectivity of a column system, S, defined by equation 28, includes a variation coefficient (β) of plate number with capacity ratio which has a large influence on the peak capacity, as shown in Fig. 18. Some typical chromatograms are given. In order to predict S for a column system from Kovat's Index, equations 40 and 41 are given to calculate the constant of the carbon number rule for squalane at different temperatures or for different stationary phases. The specific retention value of heptane on squalane at different temperatures can be calculated from equation 42. The nonpolarity index, defined by equation 43, was used to calculate the retention value of heptane on various stationary phases. In liquid chromatography, the order of elution may be reversed by changing the composition of the eluent on the same chemically bonded silica (manufactured in China). The linear relations between the log retention values of different kinds of solutes or of a single solute on the silicas of different surface areas when using the same eluent are given.     

Localized molecular orbitals and the problem of quasi-aromaticity in trinuclear molybdenum cluster compounds with cores of the type [MO3(μ3-X)(μ-Y)3] (X, Y = O, S, n = 4; X = O, Y = Cl, n = 5)

Calculations of localized molecular orbitals (LMO) and their energy levels for the cluster cores [MO₃O₄]⁴⁺, [MO₃SO₃]⁴⁺, [MO₃OS₃]⁴⁺, [Mo₃S₄]⁴⁺ and [MO₃OCl₃]⁵⁺ have been made by the use of energy-localized CNDO/2-LMO. The results of these LMO calculations show that the six-membered closed and continuous π-conjugated systems around the [MO₃Y₃] rings, each of which is formed from three synergically connected three-centered two-electron π bonds, is the most significant feature of the electronic structure for the quasi-aromatic clusters [Mo₃(μ₃-Y)(μ-X)₃]⁴⁺ (X, Y = O, S), and the size and electronegativity of the bridging Y atoms exhibit significant effects on the degree of quasi-aromaticity of these cluster compounds. For the non-aromatic reference cluster [Mo₃OCl₃]⁵⁺, the results of our calculations also show a bonding scheme with only one isolated π bond, thus leading to the loss of quasi-aromaticity; and meanwhile, there is a pair of extra electrons localized on the apical molybdenum atom of the Mo₃ triangle, thus with three Mo---Mo single bonds.     

One-Pot Formation of Carbonates from the Reactions of Carbonyl Compounds with Samarium Diiodide and Methyl Chloroformate

Treatment of carbonyl compounds with SmI₂ and methyl chloroformate in the presence of molecular sieves provides the cyclic carbonates or biscarbonates of pinacols. This one-pot reaction proceeds rapidly even with aliphatic ketones. The stereochemistry obtained by this procedure is different from that of conventional pinacolic couplings.     

嵌段离聚物的制备及其络合和缔合性质

报道了一种氢化ＳＢＳ（ＳＥＢＳ）的化学改性方法，由此得到了一种基于ＳＥＢＳ的离聚物，其中ＰＳ嵌段接有少量羧酸盐基．用动态光散射和粘度法表征了基于ＳＥＢＳ的不同配对离子的磺酸离聚物在非极性溶剂中的缔合行为，给出了缔合物存在的证据和缔合物尺寸的定量数据．ＳＥＢＳ磺酸盐离聚物与含吡啶基的无规共聚物在稀溶液和本体中能形成分子间的络合物，这从共混物溶液粘度的反常增大和本体Ｔｇ的显著增加得到了证明．用粘度法、透射电子显微镜表征和证实了ＳＥＢＳ羧酸钠离聚物在水中可以形成稳定的胶体分散．疏水粒子为表面的离子基团所稳定．     

双酚-S-双(3-甲基丙烯酰氧基-2-羟丙基)醚的聚合及其应用

以MMA为起始原料经转变为GMA,再与双酚-S反应合成了一种新的含有砜基的交联剂BisS-GMA。这种双酚-S型交联剂与MMA可以顺利地用紫外光或BPO-胺体系引发聚合。新的双酚-S型交联剂BisS-GMA与双酚-A型交联剂Bis-GMA相比,具有活性高与粘结强度高两个显著优点。它还可以和二氧化硅填料混合组成复合树脂,经光引发或BPO-DHET体系引发聚合,得到的复合树脂其物性已达到国外同类产品的水平。DHET作为促进剂要比DMT性能好,前者配制的交联剂液体组份贮存稳定性好,经半年后而不“失活”,后者配制的液体组份则在较短的时间内“失活”。     

Over 18% binary organic solar cells enabled by isomerization of non-fullerene acceptors with alkylthiophene side chains

Side-chain engineering has been demonstrated as an effective method for fine-tuning the optical, electrical, and morphological properties of organic semiconductors toward efficient organic solar cells (OSCs). In this work, three isomeric non-fullerene small molecule acceptors (SMAs), named BTP-4F-T2C8, BTP-4F-T2EH and BTP-4F-T3EH, with linear and branched alkyl chains substituted on the α or β positions of thiophene as the side chains, were synthesized and systematically investigated. The results demonstrate that the size and substitution position of alkyl side chains can greatly affect the electronic properties, molecular packing as well as crystallinity of the SMAs. After blending with donor polymer D18-Cl, the prominent device performance of 18.25% was achieved by the BTP-4F-T3EH-based solar cells, which is higher than those of the BTP-4F-T2EH-based (17.41%) and BTP-4F-T2C8-based (15.92%) ones. The enhanced performance of the BTP-4F-T3EH-based devices is attributed to its stronger crystallinity, higher electron mobility, suppressed biomolecular recombination, and the appropriate intermolecular interaction with the donor polymer. This work reveals that the side chain isomerization strategy can be a practical way in tuning the molecular packing and blend morphology for improving the performance of organic solar cells.