含多面低聚倍半硅氧烷新型杂化聚合物的合成

基于多面低聚倍半硅氧烷（POSS）的杂化聚合物是近年发展起来的一类新型有机/无机杂化材料，性能独特，应用前景广阔。本文综述了含POSS新型杂化聚合物的合成研究进展，涉及自由基溶液聚合、可控活性聚合、开环易位聚合、缩聚和配位聚合。     

Reactivity differences between molecular and surface silanols in the preparation of homogeneous and heterogeneous olefin metathesis catalysts

The reaction of Mo(N)(CH₂tBu)₃ (1) and SiO_2-(700) generates (SiO)Mo(NH)(CHtBu)(CH₂tBu) (2) when performed in C₆H₆ (material [1/SiO_2-(700)]_C6H6). The grafting occurs presumably by protonation of the nitrido ligand to form an intermediate (SiO)Mo(NH)(CH₂tBu)₃ (3), a pentacoordinated complex, which decomposes into 2 and 2,2-dimethylpropane. While [1/SiO_2-(700)]_C6H6 is highly active in olefin metathesis, [1/SiO_2-(700)]_CH2Cl2 and [1/SiO_2-(700)]_THF are poorly active or inactive catalysts respectively. In contrast, when Mo(N)(CH₂tBu)₃ reacts with a molecular silanol derivative, a soluble model of the surface of SiO_2-(700), it yields a very stable complex, (c-C₅H₉)₇Si₇O₁₂SiO-Mo(NH)(CH₂tBu)₃ (3m), which does not spontaneously generate 2,2-dimethylpropane and an alkylidene complex in contrast to the surface complex. Moreover, 3m does not catalyse olefin metathesis at room temperature as it does not already contain the initiating carbene ligand, and it is necessary to heat up the reaction mixture to 110 °C to obtain low catalytic activity. Nevertheless, the complex 3m generates well-defined metallocarbenes when heated in the presence of PMe₃: (c-C₅H₉)₇Si₇O₁₂SiO-Mo(N)(CHtBu)(P(CH₃)₃)₂ (4m) as a 10:1 mixture of its syn and anti rotamers with the loss of 2 equiv. of 2,2-dimethylpropane.     

Synthesis of functionalized polyhedral oligomeric silsesquioxane (POSS) macromers by microwave assisted 1,3-dipolar cycloaddition

In this paper we report the first synthesis of isoxazolidine and isoxazoline-POSS macromers by 1,3-dipolar cycloaddition reactions of vinyl- and styryl-POSS with N-methyl-C-ethoxycarbonylnitrone and ethoxycarbonyl nitrile oxide, promoted by microwave irradiation. The nature of the resulting cycloadducts has been determined by NOE experiments and supported by computational studies at PM3 and DFT B3LYP/6-31G* levels.     

Formation of a crosslinked POSS network by an unusual hydrosilylation: Thermo‐oxidative stabilization of the α‐cristobalite phase in its amorphous regions

A semicrystalline inorganic–organic hybrid crosslinked network containing polyhedral oligomeric silsesquioxane (POSS) cores was constructed by the unusual hydrosilylation of the terminal vinyl groups of an internal acetylene‐containing silane linker by a POSS monomer. Products from the thermal treatments of this network in either argon or air at 250, 550, and 1000 °C, respectively, were characterized by Fourier transform infrared, Solid‐state ¹³C and ²⁹Si magic angle spinning NMR, X‐ray diffraction and XPS analyses. The highly symmetrically functionalized POSS silica clusters, in the fluorite silica phase, in the network were found to remain unchanged on thermal treatment possibly due to the shielding of the silica core by the functionalities and a cancellation of thermal stresses on the silica core. Stabilization of the metastable α‐cristobalite phase, which is typically formed on cooling by a β‐ to α‐transition of the β‐cristobalite phase formed above 1400 °C, was observed in the amorphous regions in the network sample treated only to 1000 °C in air. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Physically cross‐linked networks of POSS‐capped poly(acrylate amide)s: Synthesis,morphologies, and shape memory behavior

In this work, we synthesized a novel organic–inorganic semitelechelic polymer from polyhedral oligomeric silsesquioxane (POSS) and poly(acrylate amide) (PAA) via reversible addition‐fragmentation chain transfer (RAFT) polymerization. The organic–inorganic semitelechelic polymers have been characterized by means of nuclear magnetic resonance spectroscopy, thermal gravimetric analysis, and dynamic mechanical thermal analysis. It was found that capping POSS groups to the single ends of PAA chains caused a series of significant changes in the morphologies and thermomechanical properties of the polymer. The organic–inorganic semitelechelics were microphase‐separated; the POSS microdomains were formed via the POSS–POSS interactions. In a selective solvent (e.g., methanol), the organic–inorganic semitelechelics can be self‐assembled into the micelle‐like nanoobjects. Compared to plain PAA, the POSS‐capped PAAs significantly displayed improved surface hydrophobicity as evidenced by the measurements of static contact angles and surface atomic force microscopy. More importantly, the organic–inorganic semitelechelics displayed typical shape memory properties, which was in marked contrast to plain PAA. The shape memory behavior is attributable to the formation of the physically cross‐linked networks from the combination of the POSS–POSS interactions with the intermolecular hydrogen‐bonding interactions in the organic–inorganic semitelechelics. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 587–600     

Modification of polyhedral oligomeric silsesquioxane derivatives with heck reaction as possible new bio-hybrid materials

Abstract

The regioselective synthesis of Polyhedral oligomeric silsesquioxane (POSS)-based norbornyl imide derivatives through palladium catalyzed Heck coupling reaction was reported on an effective synthetic method to organic–inorganic bio-hybrids serving as advanced materials. The reaction of POSS-based imide derivatives with various aryl iodides catalyzed by palladium acetate in the presence of triethyl amine, as the base, in DMF afforded the products in moderate yields. All new POSS derivatives were structurally characterized by FTIR, ¹H, ¹³C NMR, HRMS and GC/MS analyses.     

Morphology studies and ac electrical property of low density polyethylene/octavinyl polyhedral oligomeric silsesquioxane composite dielectrics

This paper presents the results of morphological and ac electrical investigations on low density polyethylene (LDPE) composites with octavinyl polyhedral oligomeric silsesquioxane (POSS). It has been shown that at low loadings, the frequency dependence of dielectric constant and dielectric loss for the LDPE/POSS composites showed unusual behaviors when compared with conventional (micro-sized particulates) composites. The ac breakdown strength was measured and statistical analysis was applied to the results to determine the effects of POSS loadings on the dielectric strength of LDPE. The morphological characterization showed that the presence of POSS additives apparently altered the supermolecular structure of LDPE and resulted in more homogeneous morphology when compared with the neat LDPE. The structure-property relationship was discussed and it was concluded that the final dielectric properties of the composites were determined not only by the incorporation of POSS additives but also by the supermolecular structure of LDPE. Rheological analyses of LDPE/POSS composite were also performed and the results showed that the octavinyl-POSS had good compatibility with LDPE.     

Structure and properties of low-dielectric-constant poly(acetoxystyrene-co- octavinyl-polyhedral oligomeric silsesquioxane) hybrid nanocomposite

<正>Low-dielectric-constant poly(acetoxystyrenezhi-co-octavinyl-polyhedral oligomeric silsesquioxane)(PAS-POSS) organicinorganic hybrid nanocomposite was successfully synthesized via one-step free radical polymerization and characterized by FTIR,high-resolution ~1H NMR,~(29)Si NMR,DSC,TGA,AFM,spectroscopic elhpsometry and dielectric constants measurements. The results show T_g and T_(dec) were elevated dramatically due to the incorporation of inorganic POSS cores.Spectroscopic ellipsometry and dielectric constants measurement display the incorporation of POSS into PAS homopolymer can apparently reduce the dielectric constant of materials due to the increase of relative porosity of the hybrid nanocomposites.     

Polymerization and nanocomposites properties of multifunctional methylmethacrylate POSS

Thermally induced polymerization of multifunctional methylmethacrylate POSS (MMA‐POSS) was studied in this work for preparation of polymer/POSS nanocomposites. The polymerization of MMA‐POSS could be promoted with benzoyl peroxide (BPO). Self‐assembly of POSS into a layer‐by‐layer structure in the MMA‐POSS polymer (TP‐MMA‐POSS) is observed with a transmission electron microscopy. An ultra‐low‐k value of about 1.85 is measured with TP‐MMA‐POSS. In addition, polyimide‐POSS nanocomposites are also prepared. These nanocomposites demonstrate good homogeneity and enhanced mechanical properties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5157–5166, 2008     

Star polymers with POSS via azide–alkyne click reaction

Azidopropyl‐heptaisobutyl‐substituted polyhedral oligomeric silsesquioxane (POSS‐N₃) was reacted with 1,1,1‐tris[4‐(2‐propynyloxy)phenyl]‐ethane ( 1 ) and poly(ethylene glycol) (PEG)‐b‐poly(methyl methacrylate) (PMMA) copolymer with alkyne at its center (PEG‐PMMA‐alkyne) affording the first time synthesis of 3‐arm star POSS and PEG‐PMMA‐POSS 3‐miktoarm star terpolymer, respectively, in the presence of CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as catalyst and N,N‐dimethylformamide/tetrahydrofuran as solvent at room temperature. The precursors and the target star polymers were characterized comprehensively by ¹H NMR, GPC, and DSC. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5947–5953, 2009