含金属笼型倍半硅氧烷的研究进展

倍半硅氧烷作为催化剂载体硅胶表面结构与性能研究的模型,可以通过表征其表面反应性质来直观认识硅胶负载型催化剂的作用机制。过去几十年来,倍半硅氧烷的研究呈现飞跃式的发展态势,开发出许多新化合物和新合成方法,并在一些催化过程中得到应用。将倍半硅氧烷作为金属化合物的配体,极大地丰富了元素化学的内容。本文重点介绍了合成含金属笼型倍半硅氧烷的相关进展,同时介绍了含金属笼型倍半硅氧烷在聚合物材料应用中的研究。     

周边硅笼取代的混杂酞菁卟啉三层铽单分子磁体

通过在铽的酞菁卟啉混杂三层的卟啉周边共价连接体积庞大的笼型倍半硅氧烷(POSS),得到了首个包含POSS的混 杂三层Tb₂(Pc)[T(OPOSS)₄PP]₂(1)[H₂Pc=phthalocyanine;H₂T(OPOSS)₄PP=5,10,15,20-tetra{[[N-[heptakis(isobutyl)propoxy]phenyl]octasiloxane]}porphyrin]。为了对比研究,同时合成了类似的三层化合物Tb₂(Pc)(TPP)₂(2)(H₂TPP=5,10,15,20-tetraphenyporphyrin)。尤其值得注意的是,在没有外加磁场的条件下,Tb₂(Pc)[T(OPOSS)₄PP]₂(1)和Tb₂(Pc)(TPP)₂(2)分别表现出单分子磁体和非单分子磁体的性质,这充分说明了共价连接均匀分布的POSS基团有效地分离了磁性核心,从而改善了酞菁卟啉混杂三层的磁性。     

周边硅笼取代的混杂酞菁卟啉三层铽单分子磁体

通过在铽的酞菁卟啉混杂三层的卟啉周边共价连接体积庞大的笼型倍半硅氧烷(POSS), 得到了首个包含POSS的混杂三层Tb₂(Pc)[T(OPOSS)₄PP]₂ (1)[H₂Pc=phthalocyanine;H₂T(OPOSS)₄PP=5, 10, 15, 20-tetra{[[N-[heptakis(isobutyl)propoxy]phenyl]octasiloxane]}porphyrin]。为了对比研究, 同时合成了类似的三层化合物Tb₂(Pc)(TPP)₂(2)(H₂TPP=5,10,15,20-tetraphenyporphyrin)。尤其值得注意的是, 在没有外加磁场的条件下, Tb₂(Pc)[T(OPOSS)₄PP]₂(1)和Tb₂(Pc)(TPP)₂(2)分别表现出单分子磁体和非单分子磁体的性质, 这充分说明了共价连接均匀分布的POSS基团有效地分离了磁性核心, 从而改善了酞菁卟啉混杂三层的磁性。     

Fabrication of Layer-by-layer Films of Polyhedral Oligomeric Silsesquioxanes

Layer-by-layer(LBL)self-assembly method was used to fabricate siliceous ultrathin films by using polyhedral oligomeric silsesquioxanes as building blocks.Ammonium salt of kctasilsesquioxane acid (OSi8) and bply(diallyldimethylammonium chloride)(PDDA) were altermately assembled onto CaF2 slide to form nanocomposite multilqyers,Linear build-up of the LBL films was confirmed by UV-Vis spectroscopy.IR spectrum suggests existence of OSi8 and PDDA in the LBL films.Atomic force microscopic surface topography of the LBL films indicates the OSi8 covers the entire surface of the topmost layer and shows a granular morphology.     

六面体倍半硅氧烷(POSS)杂化材料

POSS作为一种新型的有机/无机杂化材料在近10年的研究中引起了人们的极大关注,这种杂化材料可以通过不同的合成方法获得,为材料的设计提供了极大的便利。本文综述了近几年来POSS基有机/无机杂化的电致发光材料、液晶材料和POSS衍生物的自组装行为的研究进展,指出这类材料由于制作方便和热力学性能优良,在未来高科技领域中必有宽广的应用前景。     

POSS基树枝状大分子的合成与应用

树枝状大分子(dendrimer)是一种高度支化、纳米尺度的人工合成大分子,具有独特的物理化学性能和重要的应用前景。利用具有8个可官能化顶点的多面体低聚倍半硅氧烷(POSS)作为树枝状大分子的核心,可在一定程度上简化树枝状大分子繁琐的合成与分离过程,在低代数时就可获得较大的表面官能团密度,并使树枝状分子呈现球形对称结构。POSS基树枝状大分子结合了POSS和树枝状分子结构与性能的优势,是一类极具潜力的有机-无机纳米杂化材料。本文综述了近年来POSS基树枝状大分子的最新研究成果,介绍了具有代表性的POSS基树枝状大分子的合成方法以及它们在催化剂、生物材料、液晶材料和发光材料等领域的应用研究进展,并对该新型材料的发展趋势做了展望。     

生物降解高分子/笼型倍半硅氧烷纳米复合材料的制备、结晶行为与性能研究进展

由于相对较高的价格、较慢的结晶速率、较弱的力学性能、较差的热稳定性、较窄的加工窗口和较慢的生物降解速率等自身的弱点,生物降解高分子材料并未如通用高分子材料一样得到广泛应用,制备以生物降解高分子为基体的纳米复合材料是有效的改性方法之一。本文结合作者近年来在生物降解高分子改性领域中的工作,对以笼型倍半硅氧烷(POSS)作为纳米填料改性左旋聚乳酸(PLLA)和聚ε-己内酯(PCL)的研究进行简单综述,POSS可有效提高PLLA和PCL基体的结晶速率和力学性能,并促进了聚合物基体的水解过程。     

基于多面体低聚倍半硅氧烷体系的一种独特发光现象

实验发现将2种POSS（多面体低聚倍半硅氧烷）单体氨苯基异丁基POSS和八异丁基POSS置于四氢呋喃搅拌加热后，原来不发光的POSS单体表现出较强的发光。为解释这个发光现象，我们对溶剂处理前后的POSS材料进行了结构和发光性能表征，通过¹HNMR、²⁹Si NMR及红外光谱等方法表征了POSS材料在THF中加热处理前后的结构，实验结果表明，这两种POSS在处理前后结构几乎没有变化，可以保持完整的笼状结构，但处理后的POSS分子¹H NMR谱中含有少量的溶剂峰。FTIR结果也表明处理前后的POSS结构几乎不变；我们也通过XPS表征了处理后的POSS中Si原子的价态，结果表明其价态未发生变化。结合这两种POSS材料处理前后的发光性能以及结构表征结果，我们认为，这种发光现象可能与POSS的吸附效应有关，即溶剂分子进入POSS笼中，形成POSS/溶剂加合物，从而改变了原来的POSS的电子结构，使得相应的POSS材料出现发光现象。     

Synthesis and Characterization of Monofunctionalized Polyhedral Oligomeric Silsesquioxanes by Cohydrolytic and Cocondensation of Propyltrimethoxysilane and Vinyltrimethoxysilane

A monofunctional POSS [Si₈O₁₂(CH?CH₂)(C₃H₇)₇] was synthesized by the cohydrolysis and cocondensation of propyltrimethoxysilane and vinyltrimethoxysilane in methanol solvent under acidic conditions. Then, the structure of the product was investigated using FT-IR, ¹H-NMR, ²⁹Si-NMR and XRD. Experimental results indicated that the mole rate of propyls and vinyls attached on POSS was approximately 7:1, which was controlled through altering the ratio of two monomers. Furthermore, the TGA result also showed a rapid mass loss began at temperature over 218°C due to the degradation or sublimation of POSS itself. The new method, in comparison with the conventional corner-capping method, offered us another simple and effective access to preparing this kind of monofunctional POSS.     

Interfacial Activity of Amine‐Functionalized Polyhedral Oligomeric Silsesquioxanes (POSS): A Simple Strategy To Structure Liquids

Amine‐functionalized polyhedral oligomeric silsesquioxane (POSS), the smallest, monodisperse cage‐shaped silica cubic nanoparticle, is exceptionally interfacially active and can form assemblies that jam the toluene/water interface, locking in non‐equilibrium shapes of one liquid phase in another. The packing density of the amine‐functionalized POSS assembly at the water/toluene interface can be tuned by varying the concentration, the pH value, and the degree of POSS functionalization. Functionalized POSS gives a higher interface coverage, and hence a lower interfacial tension, than nanoparticle surfactants formed by interactions between functionalized nanoparticles and polymeric ligands. Hydrogen‐bonded POSS surfactants are more stable at the interface, offering some unique advantages for generating Pickering emulsions over typical micron‐sized colloidal particles and ligand‐stabilized nanoparticle surfactants.     

Rational Design and Synthesis of Hybrid Porous Polymers Derived from Polyhedral Oligomeric Silsesquioxanes via Heck Coupling Reactions

Heck coupling reactions are introduced as an efficient method to prepare porous polymers. Novel inorganic‐organic hybrid porous polymers (HPPs) were constructed via Heck coupling reactions from cubic functional polyhedral oligomeric silsesquioxanes (POSS), iodinated octaphenylsilsesquioxanes (OPS) and octavinylsilsesquioxanes (OVS) using Pd(OAc)₂/PPh₃ as the catalyst. Here, two iodinated OPS were used, IOPS and p‐I₈OPS. IOPS was a mixture with 90% octasubstituted OPS (I₈) and some nonasubstituted OPS (I₉), while p‐I₈OPS was a nearly pure compound with ≥99% I₈ and ≥93% para‐substitution. IOPS and p‐I₈OPS reacted with OVS to produce the porous materials HPP‐1 and HPP‐2, which exhibited comparable specific surface areas with S_BET of 418 ± 20 m² g⁻¹ and 382 ± 20 m² g⁻¹, respectively, with total pore volumes of 0.28 ± 0.01 cm³ g⁻¹ and 0.23 ± 0.01 cm³ g⁻¹, respectively. HPP‐1 showed a broader pore size distribution and possessed a more significant contribution from the mesopores, when compared with HPP‐2, thereby indicating that IOPS may induce more disorder because of the geometrical asymmetry. HPP‐1 and HPP‐2 possessed moderate carbon dioxide uptakes of 134 and 124 cm³ g⁻¹ at 1 bar at 195 K, making them promising candidates for CO₂ capture and storage. The synthesized porous polymers may be easily post‐functionalized using the retained ethenylene groups.

     

Detection of Single Molecule on Water Surface by Confocal Fluorescence Microscopy

In the past decade,several research groups have succeeded in observing single molecule in liquid, and more recently at silica surface in the near-field mode as well as at polymer-air interface in far-field mode. Due to the significance of air-water interface in surface chemistry, we prospect that research works on single molecule detection (SMD) of the air-water surface could open a new era in surface photochemistry and photophysics.     

1,3,5-三硝基苯在高岭石表面吸附的理论研究

构造了高岭石硅氧层和铝氧层的团簇模型(分别为Si₁₃O₃₇H₂₂和Al₆O₂₄H₃₀), 并分别在B3LYP/6-31G(d), MP2/6-31G(d)//B3LYP/6-31G(d)和B3LYP/6-311++G(d,p)//B3LYP/6-31G(d)理论水平上对1,3,5-三硝基苯(TNB)在高岭石表面的吸附性质(如优化的几何构型、 结构参数、 吸附能、 振动频率、 静电势和分子轨道等)进行了研究. 结果表明, TNB和硅氧层表面间的相互作用以静电和范德华相互作用为主; TNB与铝氧层间的相互作用以氢键为主, 且TNB和铝氧层间相互作用的能量更低, 结构更稳定.     

水分子在HZSM-5沸石原子簇上吸附的密度泛函研究

运用基于广义梯度密度泛函理论的BLYP方法研究了水分子在HZSM-5沸石原子簇不同孔道中的吸附前后的结构.结果表明水分子与HZSM-5沸石原子簇相互作用时,电子由水分子向沸石骨架转移.一个水分子吸附于HZSM-5的直孔道、扭曲孔道和交叉孔道Br(o)nsted酸位上时,均形成较稳定的中性络合物的结构,但是在不同沸石孑L道的吸附热不一样,大小顺序分别为交叉孔道＞直孔道＞扭曲孔道.当有两个水分子被吸附时,不同沸石孔道Br(o)nsted酸位上中性络合物的结构与离子性络合物的结构均有存在.     

Thermal and Surface Properties of Phenolic Nanocomposites Containing Octaphenol Polyhedral Oligomeric Silsesquioxane

Summary: We have synthesized a new polyhedral oligomeric silsesquioxane (POSS) containing eight phenol functional groups and copolymerized it with phenol and formaldehyde to form novolac‐type phenolic/POSS nanocomposites exhibiting high thermal stabilities and low surface energies. Our DSC results indicate that the glass transition temperature of these nanocomposites increased initially upon increasing their POSS content, but then decreased at POSS content above 10 wt.‐%, presumably because of the formation of relatively low molecular weight species and POSS aggregation as evidenced from MALDI‐TOF mass analyses. Our TGA analyses indicated that the 5‐wt.‐%‐mass‐loss temperatures (T_d) increased significantly upon increasing the POSS content because the incorporation of the POSS led to the formation of an inorganic protection layer on the nanocomposite's surface. XPS and contact angle data provided positive evidence to back up this hypothesis. In addition, contact angle measurements indicated a significant enhancement in surface hydrophobicity after increasing the POSS content.

Syntheses procedures of phenolic/OP‐POSS nanocomposites.     

First-principles Study of Single Tin-phthalocyanine Molecule on Ag(111) Surface

Adsorption behavior and electronic structure of tin-phthalocyanine (SnPc) on Ag(111) sur-face with Sn-up and Sn-down conformations are investigated using first-principles calcula-tions. Two predicted adsorption configurations agree well with the experimentally deter-mined structures. SnPc molecule energetically prefers to adsorb on Ag(111) surface with Sn-down conformation. The energy required to move the central Sn atom through the frame of a phthalocyanine molecule, switching from the Sn-up to Sn-down conformation, is about 1.68 eV. The simulated scanning tunneling microscopy images reproduce the main features of experimental observations. Moreover, the experimentally proposed hole attachment mech-anism is verified based on the calculated density of states of SnPc on Ag(111) with three different adsorption configurations.     

Efficient Adsorption and Extraction of Glutathione S-Transferases with Glutathione-Functionalized Graphene Oxide–Polyhedral Oligomeric Silsesquioxane Composite

Glutathione S-transferases (GSTs) are important type-II detoxification enzymes that protect DNA and proteins from damage and are often used as protein tags for the expression of fusion proteins. In the present work, octa-aminopropyl caged polyhedral oligomeric silsesquioxane (OA–POSS) was prepared via acid-catalyzed hydrolysis of 3-aminopropyltriethoxysilane and polymerized on the surface of graphene oxide (GO) through an amidation reaction. Glutathione (GSH) was then modified to GO–POSS through a Michael addition reaction to obtain a GSH-functionalized GO–POSS composite (GPG). The structure and characteristics of the as-prepared GPG composite were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), thermogravity analysis, and surface charge analysis. The specific binding interactions between glutathione and GST gave GPG favorable adsorption selectivity towards GST, and other proteins did not affect GST adsorption. The adsorption behavior of GST on the GPG composite conformed to the Langmuir isotherm model, and the adsorption capacity of GST was high up to 364.94 mg g⁻¹ under optimal conditions. The GPG-based solid-phase adsorption process was applied to the extraction of GST from a crude enzyme solution of pig liver, and high-purity GST was obtained via SDS-PAGE identification.     

金属Pt表面水蒸汽分子吸附的量子力学计算

基于电子与振动近似方法和密度泛函B3LYP理论, 氧和氢原子选择6-311G**基函数, Pt选择赝势基组LanL2DZ, 优化得到Pt-OH₂结构和微观性质, 稳态结构Pt-H₂O分子中, Pt与H₂O不在同一平面, Pt倾向于与O原子结合. 计算了100～898.15 K温度下, 水蒸汽分子在Pt表面吸附反应的热力学函数值和平衡压力, 拟合得到ΔS⁰,ΔH⁰, ΔG⁰, ln p与温度的函数关系. 室温以上ΔG⁰＞0 kJ•mol^－1, 水蒸汽分子在Pt表面不能稳定吸附; 200 K以下, ΔG⁰＜0 kJ•mol^－1, 能够稳定吸附. 计算了不同温度下水蒸汽分子在Pt表面发生解离反应的ΔG⁰和平衡压力, 室温以上ΔG⁰＞0 kJ•mol^－1. 100～898.15 K温度下, 水蒸汽分子在Pt表面不容易发生解离, 实际反应过程中以完整分子形式参与反应.