笼状硅氧烷低聚物/聚合物复合材料的研究进展

介绍了笼状硅氧烷低聚物（POSS）的概念、分类及其合成工艺,综述了POSS／聚合物复合材料的制备方法及其在提高聚合物在热稳定性、阻燃性能、医学性能、光电性能、形状记忆及表面性能等方面的应用。     

局部凸空间的弱局部一致凸性与局部一致凸性

本文引进了局部凸空间的弱局部一致凸和局部一致凸的概念,同时得到了几个与赋范线性空间几何理论中相应定理平行的结论。     

功能化POSS对硅橡胶力学性能的影响及机理研究

研究了八聚笼型倍半硅氧烷(POSS)功能化侧基的种类和用量对硅橡胶力学性能的影响。结果表明,POSS的加入使硅橡胶的拉伸强度和断裂伸长率均下降,硬度均提高。乙烯基POSS的加入显著延长了硅橡胶的正硫化时间。POSS的加入能显著降低硅橡胶的压缩永久变形,乙烯基POSS的效果比甲基POSS好;且乙烯基含量越高,压缩永久变形越小。分析了功能化POSS对硅橡胶力学性能的影响机理。     

Synthesis of poly(ε‐caprolactone)/clay nanocomposites using polyhedral oligomeric silsesquioxane surfactants as organic modifier and initiator

Poly(ε‐caprolactone)/clay nanocomposites were synthesized by in situ ring‐opening polymerization of ε‐caprolactone in the presence of montmorillonite modified by hydroxyl functionalized, quaternized polyhedral oligomeric silsesquioxane (POSS) surfactants. The octa(3‐chloropropyl) polyhedral oligomeric silsesquioxane was prepared by hydrolytic condensation of 3‐chloropropyltrimethoxysilane, which was subsequently quaternized with 2‐dimethylaminoethanol. Montmorillonite was modified with the quaternized surfactants by cation exchange reaction. Bulk polymerization of ε‐caprolactone was conducted at 110°C using stannous octoate as an initiator/catalyst. Nanocomposites were analyzed by X‐ray diffraction, transmission electron microscopy, thermo gravimetric analysis, and differential scanning calorimetry. Hydroxyl functionalized POSS was employed as a surface modifier for clay which gives stable clay separation for its 3‐D structure and also facilitates the miscibility of polymer with clay in the nanocomposites due to the star architecture. An improvement in the thermal stability of PCL was observed even at 1 wt % of clay loading. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of phosphorus‐containing polyhedral oligomeric silsesquioxanes via hydrolytic condensation of a modified silane

A simple route to synthesize a new type of phosphorus‐containing polyhedral oligomeric silsesquioxanes (DOPO–POSS) in high yield, by the hydrolytic condensation of a modified silane, is reported. The starting material was a phosphorus‐containing triethoxy silane (DOPO–VTES), which was synthesized by addition reaction between 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) and vinyl triethoxy silane (VTES). This product was subjected to hydrolytic condensation using an HCl catalyst in methanol. The new types of phosphorus‐containing POSS were obtained and characterized using ¹H, ¹³C, ²⁹Si‐NMR, MALDI‐TOF MS, XRD, DSC, and FTIR. All of these results suggested that the DOPO–POSS were amorphous mixtures of T₈, T₉(OH), and TGA curve of DOPO–POSS shows that the cage‐like compound has high thermal stability. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

复合材料POSS/TX-10/Bent的制备及其吸附性能

以多面齐聚倍半硅氧烷(POSS)、TX-10型非离子表面活性剂为改性剂对膨润土(Bent)进行复合改性制备了复合材料(POSS/TX-10/Bent),并利用亚甲基蓝研究了其吸附性能。采用XRD、XPS、EA、FTIR、SEM对POSS/TX-10/Bent进行了组成与结构表征。结果表明,POSS和TX-10型非离子表面活性剂都成功插入到膨润土层间,使得复合材料层间距增大,疏水性增强。吸附实验表明,在30℃、pH为6.52(原始值)的条件下,复合材料投加量5 g/L、吸附180 min时效果最佳。在同等吸附条件下,复合改性膨润土对亚甲基蓝的吸附能力远大于未改性的膨润土。吸附过程更符合准二级动力学模型,平衡吸附数据与Langmuir等温吸附曲线吻合较好,吸附是一个自发的吸热过程,POSS/TX-10/Bent对亚甲基蓝的理论最大吸附量为253.81 mg/g。     

笼型倍半硅氧烷（POSS）的功能化改性 及应用研究进展

有机/无机杂化材料的改性及应用是目前材料科学中最富有活力的研究领域之一。其中笼型倍半硅氧烷（Polyhedral oligomeric silsesquioxane,POSS）在分子水平上实现了有机组分与无机组分的结合,结构呈硅氧骨架连接的立体笼型,具有优异的反应活性、耐热阻燃性、多孔性和纳米尺寸效应等特性,通过化学改性可将其应用在多个领域。本文主要从官能团改性、聚合改性和配位改性三个方面阐述了POSS的改性方法,综述了POSS在耐热材料、阻燃材料、增强材料和多孔材料等领域的应用研究进展,并对POSS今后的研究方向提出了展望。可从POSS的构效关系、改性方法以及安全性等方面进行更加深入和系统的研究,以促进POSS材料更广泛的应用。     

POSS-based hybrid thermosets via photoinduced copper-catalyzed azide–alkyne cycloaddition click chemistry

An efficient approach for the preparation of inorganic/organic hybrid thermosets via photoinduced copper-catalyzed azide–alkyne cycloaddition click chemistry is established. Highly cross-linked thermoset polymers have been practically obtained by this technique using multifunctional compounds, tri-alkyne (1,1,1-tris[4-(2-propynyloxy) phenyl]-ethane) with octakis-azido-POSS or tri-azide (3,3′-((2-((3-azido-2-hydroxypropoxy)methyl)-2-ethylpropane-1,3-diyl)bis(oxy))bis(1-azidopropan-2-ol)) in the presence of Cu(II)Br₂/N,N,N′,N″,N?-pentamethyldiethylenetriamine/2-dimethoxy-2-phenyl acetophenone. The homogeneously distributed POSS nanoparticles are clearly detected in the TEM micrographs; whereas the TGA analysis shows that the obtained hybrid thermosets are thermally stable up to 360 °C and begin to lose weight at higher temperatures with a char yield of 23–50% at 800 °C.     

Effect of additive structure and size on SiO2 formation in polymer‐derived SiOC ceramics

Silicon oxycarbide (SiOC) ceramics with highly adjustable properties and microstructures have many promising applications in batteries, catalysis, gas separation, and supercapacitors. In this study, additive structures on the nucleation and growth of SiO₂ within SiOC ceramics are investigated by adding cyclic tetramethyl‐tetravinylcyclotetrasiloxane (TMTVS) or caged octavinyl‐polyhedral oligomeric silsesquioxane (POSS) to a base polysiloxane (PSO) precursor. The effects of the 2 additives on the polymer‐to‐ceramic transformation and the phase formation within the SiOC are discussed. POSS encourages SiO₂ nucleation and leads to more SiO₂ formation with significantly increased ceramic yield, which subsequently leads to higher specific surface of 1557 m²/g with a larger pore size of ～1.8 nm for the porous SiOC. High TMTVS content decreases both the specific surface area and pore volume of the resulting porous SiOCs. This study demonstrates a new approach of using Si‐rich additive POSS to increase the SiOC yield while maintaining or even increasing the specific surface area.     

Silicate-based polymer-nanocomposite membranes for polymer electrolyte membrane fuel cells

Proton-exchange membrane fuel cells have emerged as a promising emission free technology to fulfill the existing power requirements of the 21st century. Nafion^® is the most widely accepted and commercialized membrane to date and possesses excellent electrochemical properties below 80 °C, under highly humidified conditions. However, a decrease in the proton conductivity of Nafion^® above 80 °C and lower humidity along with high membrane cost has prompted the development of new membranes and techniques. Addition of inorganic fillers, especially silicate-based nanomaterials, to the polymer membrane was utilized to partially overcome the aforementioned limitations. This is because of the lower cost, easy availability, high hydrophilicity and higher thermal stability of the inorganic silicates. Addition of silicates to the polymer membrane has also improved the mechanical, thermal and barrier properties, along with water uptake of the composite membranes, resulting in superior performance at higher temperature compared to that of the virgin membrane. However, the degrees of dispersion and interaction between the organic polymer and inorganic silicates play vital roles in improving the key properties of the membranes. Hence, different techniques and solvent media were used to improve the degrees of nanofiller dispersion and the physico-chemical properties of the membranes. This review focuses mainly on the techniques of silicate-based nanocomposite fabrication and the resulting impact on the membrane properties.