Mechanism of UV photoreactivity of alkylsiloxane self-assembled monolayers

A molecular level understanding of the photoreactivity of self-assembled monolayers (SAMs) becomes increasingly important as the spatial resolution starts to be limited by the size of the resist and the spatial extent of the photochemical reactions in photoresist micropatterning. To this end, a number of surface characterization techniques were combined to understand the reactive agents, reactive sites, kinetics, and reaction pathways in the UV photoreactivity of octadecylsiloxane (ODS) SAMs. Quantitative analysis of our results provides evidence that ground state atomic oxygen is the primary reactive agent for the UV degradation of ODS SAMs. UV degradation, which follows zero-order kinetics, results in the scission of alkyl chains instead of the siloxane headgroups. Our results suggest that the top of the ODS SAMs is the preferential reactive site. Using a novel, highly surface sensitive technique, fluorescence labeling of surface species, we identified the presence of submonolayer quantities chemical functional groups formed by the UV degradation. These groups are intermediates in a proposed mechanism based on hydrogen abstraction.     

Tertiary amine-mediated synthesis of microporous carbon membranes

Microporous carbon membranes were prepared on an -alumina support by a pyrolysis of cationic tertiary amine/anionic polymer composites. The precursor solutions contain a thermosetting resorcinol/formaldehyde (RF) polymer and a cationic tertiary amine. Three types of cationic tertiary amines with different chain lengths were used, such as tetramethlammonium bromide (TMAB), tetrapropylammonium bromide (TPAB) and cetyltrimethylammonium bromide (CTAB). A porous structure was produced by a decomposition of the amine and the resulting pores assisted the further gasification of the RF polymer at high temperature. The carbon/alumina membranes have thin and continuous carbon top layers with a thickness of 1 μm. Gas permeation tests were performed using single gases of CO₂, O₂, N₂, CF₄, n-C₄H₁₀ and i-C₄H₁₀, as well as binary mixtures of CH₄/n-C₄H₁₀ and N₂/CF₄ at different temperatures between 23 and 150 °C. The carbon membrane prepared using TMAB showed separation factors higher than 650 for the CH₄/n-C₄H₁₀ mixtures and higher than 8100 for the N₂/CF₄ mixture. From the permeation of pure gases with different molecular sizes, the pore sizes of the carbon membrane prepared using TMAB, TPAB and CTAB are estimated to be 4.0, 5.0 and larger than 5.5 Å, respectively, indicating that the micropore size of the carbon membranes is controllable by using different amines.     

Swelling kinetics and release characteristic of crosslinked chitosan: Polyether polymer network (semi-IPN) hydrogels

The aqueous swelling kinetics of a series of crosslinked chitosan (cr-CS) with glutaraldehyde (GA) interpenetrating polyether hydrogels have been studied as functions of pH, the N-deacetylation degree of chitosan, the amount of crosslinking agent, the electrolyte composition in solution, temperature, and gel composition. Based on these results, the swelling mechanism of the hydrogels was discussed. The release profiles of chlorhexidini acetas from the semi-IPN were also investigated. © 1994 John Wiley & Sons, Inc.     

富勒烯化聚环氧丙基咔唑的合成与表征

通过Ｆｒｉｅｄｅｌ－Ｃｒｒａｆｔｓ反应制备了富勒烯化的聚环氧丙基咔唑，聚合物中Ｃ６０的含量最高可达７．６ｗｔ％。通过凝胶渗透色谱法测定了聚合物分子量，并采用＾上Ｈ和＾１３Ｃ－ＮＭＲ，ＩＲ，热分析及光谱等手段对其结构进行了分析与表征。     

A comparative study on photo-induced electron transfer from fluorescein to anthraquinone and injection into colloidal TiO2

A dyad-anthraquinone-methyl ester of fluorescein-and its model compound-butyl ester-were synthesized. The effects of photo-induced electron transfer from fluorescein to an organic anthraquinone acceptor and injection into inorganic colloidal TiO(2) were studied respectively. It is found that the photo-induced electron transferring to an organic acceptor is much faster than injecting into inorganic colloidal particles when fluorescein was excited by visible light. While inorganic colloidal TiO(2) was excited by UV, the electron of fluorescein will inject into TiO(2).     

Yb3+在不同基质中基态分裂能的计算分析

利用晶体场理论,推导出Yb3+离子基态(2F7/2)与Nd3+离子基态(4I9/2)最大分裂能之间的关系式为△E(2F7/2)=1.4667△E(4I9/2),从实验数据拟合得到的关系式为△E(2F7/2)=1.0987△E(4I9/2).理论计算与实验拟合存在差异,分析了出现差异的原因,认为差异主要是由相同晶体场对于不同掺杂离子的影响即晶体场参数Nv值不完全相同而引起的.     

固相热分解反应最可几机制的判断

固相热分解反应最可几机制的判断高永煜，邹文樵，冯仰婕（华东理工大学化学系上海２００２３７）关键词热分解，动力学方程，反应机制固相热分解反应机制的判断，是热分析动力学中令人感兴趣的领域。常用的方法是从含机制函数的非等温积分动力学方程出发，分别用Ｓｅｓｔ...     

钴铬水滑石的合成及表征

采用共沉淀法合成了一系列不同Co/Cr物质的量比的碳酸根型水滑石。用X－衍射、红外光谱、差热、热重、分光光度等方法对其组成和结构进行了研究。结果表明Co/Cr投料比为2到3时能形成结晶度好、纯度高的水滑石。初步推测了部分产物的组成及所含水滑石的化学式。     

Potential energy surfaces for HenNe+ ions: ab initio and diatomics-in-molecule results

The potential energy surface of He2Ne+ has been reinvestigated using a combination of ab initio and diatomics-in-molecule (DIM) calculations. In contrast to the reports of two recent studies the ion is found to have an asymmetric linear He-Ne-He structure, with no barrier to formation from the separated atoms on the ground-state surface. The He-Ne+ bond lengths at the potential minimum are 1.51 and 1.81 A, and the total bonding energy is 0.717 eV. Comparing the He2Ne+ energy to that of HeNe+, the bonding energy for the second helium atom is 0.06 eV, about 10% of that of the first He atom. The saddle point between the two equivalent minima is a symmetric structure, 0.0074 eV above the potential minimum. A symmetric geometry becomes the overall potential minimum if the 2s hole on the Ne is excluded from the reference states of a multireference configuration interaction calculation. A DIM potential was created for the HenNe+ family of ions. The DIM potential is consistent with the asymmetric He2Ne+ ion serving as a core; it predicts a slightly more asymmetric geometry than the ab initio results. Additional helium atoms form five-membered rings around the bonds of the core ion to fill the first shell and then add to the ends of the cluster. The asymmetric core ion and the highly compact structure help to account for the lack of apparent shell structure in the mass spectrometry of HenNe+ clusters. Finally, we recommend that the value De=0.63+/-0.04 eV be adopted for the ground state of HeNe+.     

Concise and Efficient Synthesis of Dehydropeptide Analogues from Unsaturated 5（4H）—Oxazolone

Some dehydropeptide analogues were directly synthesized by the reaction of unsaturated oxazolones with free amino acids.