Surface energetics,dispersion, and nanotribomechanical behavior of POSS/PP hybrid nanocomposites

Hybrid organic–inorganic polymer nanocomposites incorporating polyhedral oligomeric silsesquioxane (POSS) nanoparticles are of increasing interest for high performance materials applications. Octaisobutyl POSS/polypropylene nanocomposites were prepared at varying POSS concentrations via melt blending. The interplay of POSS molecular geometry, composition, and concentration in relation to the tribological, nanomechanical, surface energy, and bulk properties of the nanocomposites were investigated. Ultra‐low friction and enhanced hardness, modulus, and hydrophobicity were observed for the nanocomposite surfaces, with minimal changes in the bulk thermomechanical properties. Parallel AFM, SEM, TEM, and spectroscopic analyses demonstrated significant differences in POSS distribution and aggregation in the surface and the bulk, with preferential segregation of POSS to the surface. Additionally, contact angle studies reveal significant reduction in surface energy and increase in hysteresis with incorporation of POSS nanoparticles. The differences in bulk and surface properties are largely explained by the gradient concentration of POSS in the polymer matrix, driven by POSS/POSS and POSS/polymer interactions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2441–2455, 2007     

Synthesis and properties of Fe0.83V1.17O4

Thermal properties of the organic–inorganic bicontinuous nanocomposites prepared via in situ two-stage polymerization of various silanes, epoxy, and amine monomers are investigated, and the impact of filler content and its organic compatibility on thermal stability of these nanocomposites is studied. Two series of epoxy–silica nanocomposites, namely, EpSi-A and EpSi-B containing 0–20 wt% silica, are synthesized. An epoxy–silane coupling agent is employed to improve the organic compatibility of silica in EpSi–B nanocomposites. The composites synthesized via two-stage polymerization are characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry (DSC), and thermogravimetric (TG) analysis. DSC and TG/differential thermogravimetric results reveal substantially high glass transition (T _g) and excellent thermal stability of the bicontinuous nanocomposites as compared with pristine epoxy polymer. Both T _g and thermal properties, however, considerably vary depending on the organic compatibility of the nanocomposites. Significantly higher decomposition temperatures are recorded in case of EpSi-B nanocomposites owing to the chemical links between the epoxy and silica phases. Kinetic studies also show relatively higher activation energies of pyrolysis for EpSi-B nanocomposites.     

Preparation and properties of propylene/POSS copolymer with rac-Et(Ind)2ZrCl2 catalyst

An organic-inorganic hybrid copolymer was prepared by using a C₂ symmetric ansa-metallocene catalyst in conjunction with modified methylaluminoxane (MMAO). Two kinds of monovinyl substituted polyhedral oligomeric silsesquioxane (POSS) monomers were used to copolymerize with propylene. A special experiment was carried out in order to confirm the purification of the copolymerization products. The unreacted monomer was completely removed by washing with an n-hexane/ethanol mixture. Thermal properties of the propylene/POSS copolymers exhibited improved thermal stability with higher degradation temperature and char yields, demonstrating that the inclusion of inorganic POSS nanoparticles made the organic polymer matrix more thermally robust.     

Synthesis and characterization of novel PDMS nanocomposites using POSS derivatives as cross‐linking filler

We report the synthesis and characterization of novel elastomeric nanocomposites containing polyhedral oligomeric silsesquioxanes (POSS) as both the cross‐linker and filler within a polydimethylsiloxane (PDMS) polymer matrix. These polymer composites were prepared through the reaction of octasilane‐POSS (OS‐POSS) with vinyl‐terminated PDMS chains using hydrosilylation chemistry. In addition, larger super‐POSS cross‐linkers, consisting of two pendant hepta(isobutyl)POSS molecules attached to a central octasilane‐POSS core, were also used in the fabrication of the PDMS composites. The chemical incorporation of these POSS cross‐linkers into the PDMS network was verified by solid‐state ¹H magic angle spinning NMR. Based on dynamic mechanical analysis, the PDMS nanocomposites prepared with the octafunctional OS‐POSS cross‐linker exhibited enhanced mechanical properties relative to polymer systems prepared with the tetrafunctional TDSS cross‐linker at equivalent loading levels. The observed improvements in mechanical properties can be attributed to the increased dimensionality of the POSS cross‐linker. The PDMS elastomers synthesized from the larger super‐POSS molecule showed improved mechanical properties relative to both the TDSS and OS‐POSS composites due to the increased volume‐fraction of POSS filler in the polymer matrix. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2589–2596, 2009     

Click assembly of dye-functionalized octasilsesquioxanes for highly efficient and photostable photonic systems

New hybrid organic–inorganic dyes based on an azide‐functionalized cubic octasilsesquioxane (POSS) as the inorganic part and a 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BDP) chromophore as the organic component have been synthesized by copper(I)‐catalyzed 1,3‐dipolar cycloaddition of azides to alkynes. We have studied the effects of the linkage group of BDP to the POSS unit and the degree of functionalization of this inorganic core on the ensuing optical properties by comparison with model dyes. The high fluorescence of the BDP dye is preserved in spite of the linked chain at its meso position, even after attaching one BDP moiety to the POSS core. The laser action of the new dyes has been analyzed under transversal pumping at 532 nm in both the liquid phase and when incorporated into solid polymeric matrices. The monosubstituted new hybrid dye exhibits high lasing efficiency of up to 56 % with high photostability, with its laser output remaining at the initial value after 4×10⁵ pump pulses in the same position of the sample at a repetition rate of 30 Hz. However, functionalization of the POSS core with eight fluorophores leads to dye aggregation, as quantum mechanical simulation has revealed, worsening the optical properties and extinguishing the laser action. The new hybrid systems based on dye‐linked POSS nanoparticles open up the possibility of using these new photonic materials as alternative sources for optoelectronic devices, competing with dendronized or grafted polymers.     

Organic–inorganic hybrid diblock copolymer composed of poly (ε‐caprolactone) and poly(MA POSS): Synthesis and its nanocomposites with epoxy resin

Organic–inorganic hybrid diblock copolymers composed of poly(ε‐caprolactone) and poly(MA POSS) [PCL‐b‐P(MA POSS)] were synthesized via reversible addition‐fragmentation chain transfer polymerization of 3‐methacryloxypropylheptaphenyl polyhedral oligomeric silsesquioxane (MA POSS) with dithiobenzoate‐terminated poly(ε‐caprolactone) as the macromolecular chain transfer agent. The dithiobenzoate‐terminated poly(ε‐caprolactone) (PCL‐CTA) was synthesized via the atom transfer radical reaction of 2‐bromopropionyl‐terminated PCL with bis(thiobenzoyl)disulfide in the presence of the complex of copper (I) bromide with N,N,N′,N″,N″‐pentamethyldiethylenetriamine. The results of molecular weights and polydispersity indicate that the polymerizations were in a controlled fashion. The organic–inorganic diblock copolymer was incorporated into epoxy to afford the organic–inorganic nanocomposites. The nanostructures of the organic–inorganic composites were investigated by means of transmission electron microscopy and dynamic mechanical thermal analysis. Thermogravimetric analysis shows that the organic–inorganic nanocomposites displayed the increased yields of degradation residues compared to the control epoxy. In the organic–inorganic nanocomposites, the inorganic block [viz., P(MA POSS)] had a tendency to enrich at the surface of the materials and the dewettability of surface for the organic–inorganic nanocomposites were improved in terms of the measurement of surface contact angles. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Preparation,Tg improvement,and thermal stability enhancement mechanism of soluble poly(methyl methacrylate) nanocomposites by incorporating octavinyl polyhedral oligomeric silsesquioxanes

The soluble poly(methyl methacrylate‐co‐octavinyl‐polyhedral oligomeric silsesquioxane) (PMMA–POSS) hybrid nanocomposites with improved T_g and high thermal stability were synthesized by common free radical polymerization and characterized using FTIR, high‐resolution ¹H NMR, ²⁹Si NMR, GPC, DSC, and TGA. The POSS contents in the nanocomposites were determined based on FTIR spectrum, revealing that it can be effectively adjusted by varying the feed ratio of POSS in the hybrid composites. On the basis of the ¹H NMR analysis, the number of the reacted vinyl groups on each POSS molecules was determined to be about 6–8. The DSC and TGA measurements indicated that the hybrid nanocomposites had higher T_g and better thermal properties than the pure PMMA homopolymer. The T_g increase mechanism was investigated using FTIR, displaying that the dipole–dipole interaction between PMMA and POSS also plays very important role to the T_g improvement besides the molecular motion hindrance from the hybrid structure. The thermal stability enhances with increase of POSS content, which is mainly attributed to the incorporation of nanoscale inorganic POSS uniformly dispersed at molecular level. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5308–5317, 2007     

A kinetic study of the thermal and thermal oxidative degradations of new bridged POSS/PS nanocomposites

The thermal degradation of a series of three novel bridged polyhedral oligomeric silsesquioxanes (POSS)/polystyrene (PS) nanocomposites, at different POSS content (3%, 5% and 10%), was studied in both inert (flowing nitrogen) and oxidative (static air) atmospheres, in order to investigate the effects of this new dumbbell-shaped structure on the filler–polymer interaction and then on the thermal stability of the obtained materials. Nanocomposites were synthesized by in situ polymerization of styrene in the presence of POSS which has not polymerizable groups, aiming to obtain well dispersed POSS/PS systems. The actual filler concentration in the obtained nanocomposites was checked by ¹H NMR spectroscopy. Scanning electron microscopy (SEM) and FTIR spectroscopy evidenced the presence of filler–polymer interactions. Degradations were carried out into a thermobalance, in the scanning mode, at various heating rates, and the characteristic parameters of thermal stability, namely temperature at 5% mass loss (T₅%) and the activation energy (E_a) of degradation, of the various nanocomposites were determined. The results were discussed and interpreted.     

Functional inorganic nanofillers for transparent polymers

The integration of inorganic nanoparticles into polymers has been used for the functionalization of polymer materials with great success. Whereas in traditional polymer composites, micron sized particles or agglomerates typically cause significant light scattering hampering optical applications, in nanocomposites the particle dimensions are small enough for the production of highly transparent composites. A challenge for the generation of such materials is to develop an integrated synthesis strategy adapting particle generation, surface modification and integration inside the polymer. Surface grafting using polymerizable surfactants or capping agents allows for linking the particles to the polymer. Novel techniques such as in situ polymerization and in situ particle processing are beneficial to avoid aggregation of inorganic particles inside the polymer matrix. The functions associated with inorganic fillers are widespread. Layered silicates and related materials are nowadays commercially available for improving mechanical and barrier properties in packaging. With the availability of highly transparent materials, the focus has shifted towards optical functions such as luminescence and UV-protection in transparent polymers. IR-active fillers are used in laser-holography for transparent poly(methyl methacrylate) (PMMA) nanocomposites. Refractive index modulation and ultrahigh refractive index films were developed based on inorganic materials such as PbS. The integration of magnetic nanoparticles has a great potential for applications such as electromagnetic interference shielding and magneto-optical storage.This tutorial review will summarize functions associated with the integration of inorganic nanofillers in polymers with a focus on optical properties.     

Recent Advances in Polyurethane/POSS Hybrids for Biomedical Applications

Advanced organic-inorganic materials-composites, nanocomposites, and hybrids with various compositions offer unique properties required for biomedical applications. One of the most promising inorganic (nano)additives are polyhedral oligomeric silsesquioxanes (POSS); their biocompatibility, non-toxicity, and phase separation ability that modifies the material porosity are fundamental properties required in modern biomedical applications. When incorporated, chemically or physically, into polyurethane matrices, they substantially change polymer properties, including mechanical properties, surface characteristics, and bioactivity. Hence, this review is dedicated to POSS-PU composites that have recently been developed for applications in the biomedical field. First, different modes of POSS incorporation into PU structure have been presented, then recent developments of PU/POSS hybrids as bio-active composites for scaffolds, cardiovascular stents, valves, and membranes, as well as in bio-imaging and cancer treatment, have been described. Finally, characterization and methods of modification routes of polyurethane-based materials with silsesquioxanes were presented.     

Hybrid inorganic/organic crosslinked resins containing polyhedral oligomeric silsesquioxanes

The incorporation of both monofunctional and multifunctional polyhedral oligomeric silsesquioxane (POSS) derivatives into crosslinked resins has been conducted as a route to synthesize hybrid organic/inorganic nanocomposites. The central cores of POSS molecules contain an inorganic cage with (SiO_1.5)_n stoichiometry where n=8,10 and 12. Each Si atom is capped with one H or R function giving an organic outer shell surrounding the nanometer-sized inorganic inner cage. By including polymerizable functions on the R groups, a hybrid organic/inorganic macromer is obtained which can be copolymerized with organic monomers to create thermoplastic or thermoset systems. We have focused on incorporating POSS derivatives into crosslinking resins of the following types: (1) dicyclopentadiene (2) epoxies (3) vinyl esters (4) styrene-DVB (5) MMA/1,4-butane dimethacrylate (6) phenolics and (7) cyanate esters. One goal has been to determine if molecular dispersion of the POSS macromers has been achieved or if various degrees of aggregation occur during crosslinked resin formation. As network formation proceeds, a kinetic race between POSS molecular incorporation into the network versus phase separation into POSS-rich regions (which then polymerize) occurs. Ultimately, we hope to determine the effects of such microstructural features on properties. Combustion of these hybrids creates a SiO₂-like surface layer that retards flame spread. Dynamic mechanical properties have been studied.     

Combustion and thermal properties of epoxy/phenyltrisilanol polyhedral oligomeric silsesquioxane nanocomposites

Organic–inorganic hybrid composites of epoxy and phenyltrisilanol polyhedral oligomeric silsesquioxane (Ph₇Si₇O₉(OH)₃, POSS-triol) were prepared via in situ polymerization of epoxy monomers. The nanocomposites of epoxy with POSS-triol can be prepared in the presence of metal complex latent catalyst, aluminum triacetylacetonate ([Al]) for the reaction between POSS-triol and diglycidyl ether of bisphenol A (DGEBA). The dispersion morphology of organic–inorganic hybrid was characterized by scanning electronic microscopy (SEM). The thermostability of composites was evaluated by thermal gravimetric (TG) analysis. The flammability was evaluated by cone calorimeter test. The presence of [Al] latent catalyst leads to a decrease in combustion rate with respect to epoxy and epoxy/POSS composites as well as reduction in smoke, CO and CO₂ production rate. The effect of [Al] is to reduce the size of spherical POSS particles from 3–5 μm in epoxy/POSS to 0.5 μm in epoxy/POSS[Al]. Furthermore, POSS with smaller size may form compact and continue char layer on the surface of composites more efficiently.     

A design of shape memory networks of poly(ε‐caprolactone)s via POSS‐POSS interactions

In this contribution, we reported a design of shape memory networks of poly(ε‐caprolactone)s (PCLs) via POSS‐POSS interactions. First, a series of novel organic‐inorganic PCL stars with polyhedral oligomeric silsesquioxane (POSS) termini were synthesized via the combination of ring‐opening polymerization of ε‐caprolactone and the copper (I)‐catalyzed cycloaddition of alkynyl with azido groups. It was found that the organic‐inorganic PCL stars significantly displayed shape memory properties with about 100% of recovery. The morphological observation showed that in the organic‐inorganic PCL stars, the POSS cages at the ends of PCL chains were self‐organized into the spherical POSS microdomains with the size of 10 to 20 nm in diameter. The POSS microdomains behaved as the netpoints, resulting in the formation of physically crosslinked networks. The novel physically crosslinked networks endowed the organic‐inorganic nanocomposites with shape memory properties.     

八苯基笼型倍半硅氧烷的官能化及其在高分子纳米复合材料中的应用

笼型倍半硅氧烷（POSS）是具有独特分子结构的有机硅化合物,无机硅氧骨架核心为其提供良好的硬度和热稳定性,外围有机基团可增强与聚合物基体间的相容性,以它为前驱体可以制备分子级分散的有机／无机纳米高分子杂化材料。近年来,全芳香结构的八苯基笼型倍半硅氧烷因其高的耐热性和官能化方法的多样性尤其得到关注。本文重点综述了八苯基笼...     

倍半硅氧烷改性环氧树脂的研究进展

倍半硅氧烷是近年发展起来的一种分子水平的有机无机杂化材料。文章介绍了倍半硅氧烷的结构、合成以及笼型倍半硅氧烷（POSS）基高分子复合材料的结构及合成方法。倍半硅氧烷改性聚合物可以提高聚合物的热性能、阻燃性能和物理机械性能等。文章综述了倍半硅氧烷改性环氧树脂的研究进展。     

Morphology and thermal properties of polyhedral oligomeric silsesquioxane/polybutadiene nanocomposites prepared by anionic polymerization

The morphology and thermal properties of Allylisobutyl Polyhedral Oligomeric Silsesquioxane (POSS)/Polybutadiene (PB) nanocomposites prepared through anionic polymerization technique were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results of XRD, SEM and TEM showed that the aggregation of POSS in PB matrix occurred obviously, forming crystalline domains and the size of POSS particles increased with increasing POSS content. The DSC and TGA results indicated that the glass transition temperature (T _g) of the nanocomposites was significantly increased and the maximum degradation temperature (T _dmax) of nanocomposites was slightly increased compared with pure PB, implying an increase in thermal stability.     

多面体笼型倍半硅氧烷纳米杂化低介电材料的研究

多面体笼型倍半硅氧烷( POSS)是由O-Si-O链接的纳米大小的笼型无机芯[(SiO1.5)n]和外围有机取代基团（活性或惰性）组成,这种独特的结构为杂化功能材料的制备提供了重要的平台与基础。本文从低介电材料结构对性能的影响,以及低介电性能的形成机理,综述了当前低介电材料制备方法,尤其是多面体笼型倍半硅氧烷( POSS)在低介电材料控制制备的研究进展,为该领域新材料设计提供借鉴。     

Synthesis and self‐assembly of tadpole‐shaped organic/inorganic hybrid poly(N‐isopropylacrylamide) containing polyhedral oligomeric silsesquioxane via RAFT polymerization

Aminopropylisobutyl polyhedral oligomeric silsesquioxane (POSS) was used to prepare a POSS‐containing reversible addition‐fragmentation transfer (RAFT) agent. The POSS‐containing RAFT agent was used in the RAFT polymerization of N‐isopropylacrylamide (NIPAM) to produce tadpole‐shaped organic/inorganic hybrid Poly(N‐isopropylacrylamide) (PNIPAM). The results show that the POSS‐containing RAFT agent was an effective chain transfer agent in the RAFT polymerization of NIPAM, and the polymerization kinetics were found to be pseudo‐first‐order behavior. The thermal properties of the organic/inorganic hybrid PNIPAM were also characterized by differential scanning calorimetry. The glass transition temperature (T_g) of the tadpole‐shaped inorganic/organic hybrid PNIPAM was enhanced by POSS molecule. The self‐assembly behavior of the tadpole‐shaped inorganic/organic hybrid PNIPAM was investigated by atomic force microscopy and dynamic light scattering. The results show the core‐shell nanostructured micelles with a uniform diameter. The diameter of the micelle increases with the molecular weight of the hybrid PNIPAM. Surprisingly, the micelle of the tadpole‐shaped inorganic/organic hybrid PNIPAM with low molecular weight has a much bigger and more compact core than that with high molecular weight. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7049–7061, 2008     

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     

高折射率聚合物-无机纳米光学杂化材料的设计与制备及其应用

传统的高折射率聚合物光学材料,可以通过向聚合物中引入一些芳香环,含硫基团以及除氟以外的其他卤素原子来提高聚合物光学材料的折射率,但是就目前的研究现状来看,这类纯聚合物光学材料的折射率一般都低于1.8.而将具有高折射率的无机纳米粒子引入到聚合物中,所制备的聚合物-无机纳米光学材料的折射率能够达到1.8以上.而且这类高折射率聚合物-无机纳米光学杂化材料同时具有高分子光学材料和无机材料的双重优点,具有广泛的应用前景.鉴于当前高折射率聚合物-无机纳米光学杂化材料发展之迅速和其研究与开发的重要性,并结合目前国内外的研究现状,本文就高折射率聚合物-无机纳米光学杂化材料的设计、制备方法及其相关应用做一个比较系统的介绍,同时对这类材料在未来研究中所应注意的问题也提出了相应的看法.