Octaaminophenyl Polyhedral Oligomeric Silsesquioxane Research Articles

Precisely Designed Morphology and Surface Chemical Structure of Fe-N-C Electrocatalysts for Enhanced Oxygen Reaction Reduction Activity.

Fe-N-C materials have been regarded as one of the potential candidates to replace traditional noble-metal-based electrocatalysts for the oxygen reduction reaction (ORR). It is believed that the structure of carbon support in Fe-N-C materials plays an essential role in highly efficient ORR. However, precisely designing the morphology and surface chemical structure of carbon support remains a challenge. Herein, we present a novel synthetic strategy for the preparation of porous carbon spheres (PCSs) with high specific surface area, well-defined pore structure, tunable morphology and controllable heteroatom doping. The synthesis involves Schiff-based polymerization utilizing octaaminophenyl polyhedral oligomeric silsesquioxane (POSS-NH2) and heteroatom-containing aldehydes, followed by pyrolysis and HF etching. The well-defined pore structure of PCS can provide the confinement field for ferroin and transform into Fe-N-C sites after carbonization. The tunable morphology of PCS can be easily achieved by changing the solvents. The surface chemical structure of PCS can be tailored by utilizing different heteroatom-containing aldehydes. After optimizing the structure of PCS, Fe-N-C loading on N,S-codoped porous carbon sphere (NSPCS-Fe) displays outstanding ORR activity in alkaline solution. This work paves a new path for fabrication of Fe-N-C materials with the desired morphology and well-designed surface chemical structure, demonstrating significant potential for energy-related applications.

Thermal, mechanical, and tribological properties of epoxy polymer/EPU blends reinforced by low concentration of octaaminophenyl POSS

AbstractEpoxy matrix nanocomposites were prepared by diglycidyl ether of bisphenol A (DGEBA) modified with epoxide polyurethane (EPU) containing oxazone‐group and reinforced by low concentrations of octaaminophenyl polyhedral oligomeric silsesquioxane (OAPOSS). The thermal, mechanical, and thermomechanical properties of as‐prepared hybrid nanocomposites were studied. The results demonstrate that the thermal stability, tensile strength, glass transition temperature, and storage modulus of epoxy polymer/EPU blends are all significantly improved with OAPOSS as an reinforcement. The inclusion of EPU in the epoxy polymer helps improve the toughness of the matrix, providing higher impact strength, and higher elongation at break. Tribological testing shows that the wear rate of the hybrid nanocomposite is reduced by more than 80% at 0.1 wt% OAPOSS compared with pure epoxy‐EPU, while the friction coefficient is nearly unchanged. SEM‐EDS analysis of worn scar indicates that the wear mechanism of OAPOSS incorporated hybrid composites is the coexistence of abrasive wear and adhesive wear. The improved properties are due to the uniform dispersion of OAPOSS in the epoxy‐EPU matrix and network formation by cross‐linking and chemical bonds from OAPOSS reacted with epoxy‐EPU matrix.

The interfacial structure and dynamics in a polymer nanocomposite containing small attractive nanoparticles: a full atomistic molecular dynamics simulation study.

We study the interfacial structure and dynamics of a polymer nanocomposite (PNC) composed of octaaminophenyl polyhedral oligomeric silsesquioxane (OAPS) and poly(2-vinylpyridine) (P2VP) by performing full atomistic molecular dynamics simulations. There are eight aminophenyl groups grafted on the surface of the OAPS particle and the particle has a size comparable to the Kuhn segment of P2VP. These aminophenyl groups can form hydrogen bonds (HBs) with pyridine rings from surrounding P2VP chains. We found that OAPS can form ∼2 HBs on average with surrounding polymer chains. The effect of the HBs is investigated in detail by either switching on or off these HBs in our simulation. By analyzing the interfacial static packing structure and dynamic properties, we demonstrate that the system has an ∼1 nm interface width, similar to the OAPS particle size. We also found that HBs can prevent the further penetration of polymers into the inner zone (grafting layer) of the OAPS, and therefore keep the P2VP chains in the outer layer (>1 nm), remaining bulk-like, which is well consistent with experimental results. In addition, we found that NP diffusion is coupled to the absorbed polymer chains, which also dramatically slows down the diffusion of polymer segments in return. The core-shell model in which the NP and absorbed polymers diffuse as a single object is validated here at the full atomistic level. These results provide atomistic insights into the unique structure and dynamics in the small attractive NP-polymer interfacial region. We hope these results will be helpful for the understanding of peculiar phenomena in attractive polymer nanocomposites containing small NPs.

Synthesis, characterization, and properties of novel UV-resistant poly(urethane-imide)/POSS nanocomposite

In this study, a series of hybrid nanocomposites composed of poly(urethane-imide) (PUI), fluoroethylene vinyl ether copolymers, and octa-aminophenyl polyhedral oligomeric silsesquioxane (POSS) were successfully prepared. Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), contact angle analysis, thermogravimetric analysis (TGA), and dynamic mechanical analysis were used to characterize the hybrid nanocomposites, which were found to have excellent thermostability, mechanical strength, and ultraviolet (UV) resistance. The SEM results showed that POSS nanoparticles, at low content level, could disperse homogeneously in the PUI matrix. The TGA results confirmed that the thermostability of the hybrid nanocomposites was significantly improved by the addition of POSS. Moreover, the UV-resistant property of the nanocomposites was evaluated based on the change in mechanical property and weight loss caused by the UV radiation. POSS (5 wt%) achieved the highest efficiency in enhancing the UV resistance of the nanocomposites. After UV radiation, the tensile modulus of the nanocomposite without POSS decreased to 187 MPa, and the mass loss was 7.26%. In contrast, the tensile modulus of the nanocomposite containing 5 wt% POSS increased from 412 MPa to 444 MPa, and the mass loss was only 3.76%.

Directly grafting octa(aminophenyl) polyhedral oligomeric silsesquioxane onto carbon fibers for superior interfacial strength and hydrothermal aging resistance of silicone resin composites

Introducing nano-scale reinforcements into carbon fiber (CF)-matrix interface is a useful method to enhance interfacial strength of composites. In this work, we demonstrated a facile and high efficient strategy of preparing octa(aminophenyl) polyhedral oligomeric silsesquioxane (OapPOSS)/CF hierarchical reinforcements (CF-g-POSS) by directly grafting OapPOSS on CFs by covalent bonding. OapPOSS distributed on fiber surfaces uniformly, and enhanced surface polarity as well as roughness significantly. CF-g-POSS exhibited a low contact angle and high surface free energy, which helped to change the wettability between CF and the matrix. Simultaneous enhancements of interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of CF-g-POSS/methylphenylsilicone resin (MPSR) composites were achieved, increasing 47.83% in IFSS and 59.04% in ILSS compared to those of untreated composites. These enhancements could be attributed to OapPOSS interface with providing sufficient covalent bonding and strong mechanical interlocking. Additionally, anti-hydrothermal aging behaviors were also increased obviously owing to the introduction of SiOSi bonds at the interface.

Enhancing the dyeability of poly(lactic acid) fiber with natural dyes of alizarin, lawsone, and indigo

To dye poly(lactic acid) (PLA) fiber with natural dyes has gained importance in recent years due to the production of the fully eco-friendly textile products. In this study, pure and modified PLA fibers with two different POSS nanoparticles, namely N-phenyl aminopropyl POSS (AP-POSS) and octa (aminophenyl) polyhedral oligomeric silsesquioxane (OAPPOSS), are dyed with three different natural dyes including alizarin, lawsone and indigo. The effects of the dyeing conditions including dyeing temperature and time, POSS nanoparticle concentration, natural dye types and concentrations are investigated on the dyeability properties of the PLA fiber samples. The wash and light fastness of the fiber samples are also investigated. According to the dyeability results, it is concluded that POSS nanoparticles are effective for increasing the dyeability of the PLA fiber with all natural dyes used in this study. As the added amount of the POSS nanoparticle increases, the dyeability of the PLA fiber increases. When the performances of the POSS nanoparticles are compared, it is seen that OAP-POSS is more effective than the AP-POSS nanoparticle.

Improving the dyeability of poly (lactic acid) fiber using octa (aminophenyl) POSS nanoparticle during melt spinning

Disperse dye structure affects the dyeability of poly (lactic acid) (PLA) fiber due to the low dyeing temperature and the short dyeing time. Thus, the dye uptake value of PLA fiber is low for some disperse dyes and needs to be improved. In this study, the dyeability of PLA fiber is improved with the addition of synthesized octa (aminophenyl) polyhedral oligomeric silsesquioxane (OAP-POSS) nanoparticle during the melt spinning process. The effects of dyeing conditions including dyeing temperature and time, OAP-POSS concentration, disperse dye types, and concentrations are investigated on the dyeability properties of PLA fiber samples. The tensile, thermal, and morphological properties of the fiber samples are also characterized by tensile testing, differential scanning calorimetry, scanning electron microscopy, and transmission electron microscopy. It is concluded that the percent crystallinity and the tensile strength of pure PLA fiber decrease as the added amount of OAP-POSS increases. According to the dyeing results, OAP-POSS, which behaves as a good sorbent for the disperse dyes used in this study, greatly improves the dyeability of PLA fiber, especially for disperse dyes with low dye uptake values.

Porous POSS-PANI nanofibre from interfacial polymerization and hydrothermal approach

Nowadays, novel applications for polyaniline (PANI) make new demands on its morphology controlling, and designing novel PANI or PANI composite polymeric materials has been more and more attractive. In this work, octaaminophenyl polyhedral oligomeric silsesquioxane (POSS) was employed to prepare nanostructured PANI composites via controlled fabrication. By interfacial copolymerization, fibrous nanostructure was obtained. The size and morphology of this structure was adjusted by changing POSS to OAPS ratio: the size increased from about 20 to 200 nm when the molar ratio of POSS in the composites increased from 0.5 to 2.0 mol %. More importantly, further hydrothermal treatment for the samples with higher POSS concentration resulted in mesoporous structure on a more microscopic scale, which helps to improve the thermal stability. In the total synthesis, POSS played an important role in the morphology controlling of the composites.

Preparation and properties of polyhedral oligomeric silsesquioxane/epoxy hybrid resins

Octaaminophenyl polyhedral oligomeric silsesquioxane (OAPS) was synthesized using three-step method and used to modify o-cresol-novolac epoxy resin (ECN) for printed circuit board. The influence of OAPS on the reactivity and the final properties of the hybrid networks were evaluated. The intercrosslinking reaction between ECN and OAPS was confirmed by Fourier transform infrared spectra. The ECN/OAPS hybrids have better impact strength, higher electrical resistivity and thermal stability, lower water absorption than the unmodified ECN. The volume resistivity and surface resistivity of the hybrids increase by an order of magnitude or more compared to the neat epoxy. The thermal stability of the hybrids improves by the incorporation of OAPS; the initial decomposition temperature and char yield show an increasing tendency up to 4 wt% loading of OAPS. The hybrids exhibit higher storage modulus and glass transition temperature (Tg) than the neat epoxy. The Tg of the hybrids greatly improves up to 153.3°C at 3 wt% content, much higher than 119.4°C of the neat epoxy. POLYM. COMPOS., 34:1753–1760, 2013. © 2013 Society of Plastics Engineers

Cure Kinetics and Thermal Properties of Octa(aminophenyl)-POSS/Bromobisphenol A Epoxy Resin Nanocomposites

The tetrabromobisphenol A epoxy resin (TBBPAER) was synthesized and Octa(aminophenyl) polyhedral oligomeric silsesquioxane (OAP-POSS) was used as a curing reagent of TBBPAER. The cure kinetics, the glass transition temperature, and the flame resistance of OAP-POSS/TBBPAER nanocomposites were investigated. The results show that the curing reaction could be described by the autocatalytic Šesták-Berggren (S-B) model. The average activation energy E a is 129.59 KJ/mol, the maximal mechanical loss temperature (T p) is 166°C, when the molar ratio (N s) of amino group to epoxy group is 0.5. The oxygen index for fire resistance is 46 ∼ 49 for different amounts of OAP-POSS.

Preparation and Thermal Properties of Boron-Containing o-Cresol-Formaldehyde Resin/Octa(aminophenyl)-POSS Nanocomposites

The boron-containing o-cresol-formaldehyde resin (BoCFR) and octa(aminophenyl) polyhedral oligomeric silsesquioxane (OAP-POSS) were synthesized, and the BoCFR/OAP-POSS nanocomposite prepared via an in-situ method. The curing process of the resin was characterized by Fourier transform infrared (FTIR). The thermal properties and dynamic mechanical properties of the nanocomposites were investigated. The results show that the maximal mechanical loss temperature (Tp) increased with increasing OAP-POSS content. When the content of OAP-POSS was 10 wt% the Tp was over 200°C, 27°C higher than the pure BoCFR. The BoCFR/OAP-POSS nanocomposite had better thermal stablitity than the pure BoCFR. The residual weight of the o-cresol-formaldehyde resin was only 6.13 wt% at 600°C. But the residual weight of the pure BoCFR was 55.73 wt% at 600°C, and the residual weights of the BoCFR nanocomposites were all higher than pure BoCFR. The residual weight of the BoCFR nanocomposite was 63.2 wt% at 600°C and 21.83 wt% at 900°C when the OAP-POSS content was 10 wt%. The weight loss of BoCFR/OAP-POSS nanocomposite can be divided primarily into two temperature stages, from 430°C to 550°C and from 550°C to 900°C. The main thermal degradation reaction follows first order kinetics.

Epoxy hybrid composites cured with octaaminophenyl polyhedral oligomeric silsesquioxane

AbstractPolyhedral oligomeric silsesquioxane‐containing hybrids of epoxy resins are prepared via the cocuring reaction between octaaminophenyl polyhedral oligomeric silsesquioxane (OAPS) and brominated epoxy resin (EP). The gel time, dispersion, thermal properties, mechanical properties, water absorption, and dielectric properties of the OAPS/EP composites are studied. The gel time of the 1 wt % OAPS composites is significantly higher compared with that of the epoxy resin control. Wide angle X‐ray diffraction and scanning electron microscopy show that, at the molecular level, the appropriate amount of POSS cages was dispersed in the epoxy matrix because the POSS monomer participated in the crosslinking reaction. The thermal and mechanical properties of the composites are enhanced as 1 wt % OAPS was added to the epoxy system. The water absorption of the 1 wt % OAPS composite significantly declines. The dielectric constant of the 1 wt % OAPS composite is 0.5 less than that of the epoxy resin control in the range of 100 Hz–40 MHz. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Thermal and dynamic mechanical properties of epoxy resin/poly(urethane‐imide)/polyhedral oligomeric silsesquioxane nanocomposites

AbstractLinear isocyanate‐terminated poly(urethane‐imide) (PUI) with combination of the advantages of polyurethane and polyimide was directly synthesized by the reaction between polyurethane prepolymer and pyromellitic dianhydride (PMDA). Then octaaminophenyl polyhedral oligomeric silsesquioxane (OapPOSS) and PUI were incorporated into the epoxy resin (EP) to prepare a series of EP/PUI/POSS organic–inorganic nanocomposites for the purpose of simultaneously improving the heat resistance and toughness of the epoxy resin. Their thermal degradation behavior, dynamic mechanical properties, and morphology were studied with thermal gravimetric analysis (TGA), dynamic mechanical analysis (DMA), and transmission electron microscope (TEM). The results showed that the thermal stability and mechanical modulus was greatly improved with the addition of PUI and POSS. Moreover, the EP/PUI/POSS nanocomposites had lower glass transition temperatures. The TEM results revealed that POSS molecules could self assemble into strip domain which could switch to uniform dispersion with increasing the content of POSS. All the results could be ascribed to synergistic effect of PUI and POSS on the epoxy resin matrix. Copyright © 2010 John Wiley & Sons, Ltd.

Polyhedral Oligomeric Silsesquioxane (POSS) Nanoscale Reinforcement of Thermosetting Resin from Benzoxazine and Bisoxazoline

AbstractSummary: The reaction between octaaminophenyl polyhedral oligomeric silsesquioxane (OAPS) and 2,2′‐(1,3‐phenylene)‐bis(4,5‐dihydro‐oxazoles) (PBO) over different temperature ranges was confirmed by FT‐IR spectroscopy. The OAPS was used to modify benzoxazine (BZ) in the presence of PBO. The novel polybenzoxazine (PBZ)‐PBO/OAPS hybrid nanocomposite was prepared by solvent methods. Dynamic mechanical analyses indicated that the nanocomposites exhibited much higher Tg values than the pristine PBZ and PBZ‐PBO resin, and the storage modulus of the nanocomposites was maintained at higher temperatures, although only a small amount of OAPS was incorporated into the systems. Dynamic thermogravimetric analysis showed that the thermal stability of the hybrid was also improved by the inclusion of OAPS.DMA of PBZ (a), PBZ‐PBO (b), and PBZ‐PBO/OAPS nanocomposites (c–e).magnified imageDMA of PBZ (a), PBZ‐PBO (b), and PBZ‐PBO/OAPS nanocomposites (c–e).

Epoxy Resin Containing Octamaleimidophenyl Polyhedral Oligomeric Silsesquioxane

AbstractSummary: Octamaleimidophenyl polyhedral oligomeric silsesquioxane (OmipPOSS) was synthesized via the imidization reaction between octaaminophenyl polyhedral oligomeric silsesquioxane (OapPOSS) and maleic anhydride, and it was characterized by means of Fourier transform infrared (FTIR) and NMR spectroscopies. OmipPOSS was further employed to prepare epoxy hybrids. The thermosetting hybrids containing OmipPOSS up to 10 wt.‐% were obtained via in situ polymerization of diglycidyl ether of bisphenol A (DGEBA) and 4,4′‐diaminodiphenylmethane (DDM) in the presence of OmipPOSS. High‐resolution transmission electronic microscopy (TEM) indicates that the nanometer‐scaled dispersion of POSS molecules was obtained, suggesting that the nanocomposites were successfully prepared. The results of DSC showed that the glass transition temperatures (Tg's) of the POSS‐containing nanocomposites are dependent on the content of POSS in the nanocomposites. When the contents of POSS are less than 5 wt.‐%, the nanocomposites displayed the enhanced glass transition temperatures (Tg's) in comparison with control epoxy. Thermogravimetric analysis (TGA) showed that all the nanocomposites containing POSS displayed improved char yield, suggesting the flame retardance of the materials is improved. magnified image

Polyurethane Networks Nanoreinforced by Polyhedral Oligomeric Silsesquioxane

AbstractSummary: Octaaminophenyl polyhedral oligomeric silsesquioxane (OapPOSS) was used as a crosslinking agent together with 4,4′‐methylenebis‐(2‐chloroaniline) to prepare polyurethane networks containing POSS. Fourier transform infrared spectroscopy (FT‐IR), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) were employed to characterize the POSS‐reinforced polyurethane. The POSS‐containing PU networks displayed enhanced glass transition temperatures (Tgs) and the storage moduli of the networks of the glassy state and rubber plateaus were also observed to be significantly higher than that of the control polyurethane although only a small amount of POSS was incorporated into the systems. The results can be ascribed to the significant nanoscale reinforcement effect of POSS cages on the polyurethane matrix. TGA results showed the thermal stability was also improved with incorporation of POSS into the system.Dynamic mechanical spectra of PU and PU nanocomposites containing POSS.imageDynamic mechanical spectra of PU and PU nanocomposites containing POSS.

A Novel Photocrosslinkable Polyhedral Oligomeric Silsesquioxane and Its Nanocomposites with Poly(vinyl cinnamate)

A novel photosensitive octacinnamamidophenyl polyhedral oligomeric silsesquioxane (OcapPOSS) was synthesized via the reaction between cinnamoyl chloride and octaaminophenyl polyhedral oligomeric silsesquioxane (OapPOSS). The photosensitive OapPOSS was characterized by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), and ultraviolet (UV)-visible spectroscopy. The full miscibility of OcapPOSS with the photosensitive polymer poly(vinyl cinnamate) (PVCIN) allows one to prepare the PVCIN−OcapPOSS hybrid nanocomposites. By initiating in situ UV photocrosslinking reaction of PVCIN in the presence of the photosensitive OcapPOSS, the PVCIN−POSS nanocomposites were obtained with the content of POSS up to 40 wt %. In terms of the result of FTIR spectroscopy, it is noted that the photocrosslinking rates of the PVCIN/POSS hybrids were slightly lower than those of the precursors, which could be ascribed to the nanoreinforcement of POSS cages on the polymer matrix. The inclusion of POSS cages could restrict the mobility of PVCIN macromolecular chains and thus hinder the formation of tetrabutane rings. The differential scanning calorimetric (DSC) results showed that the glass transition temperatures (Tgs) of the nanocomposites were significantly higher than that of the control PVCIN. Thermogravimetric analysis (TGA) showed that all the PVCIN nanocomposites containing POSS displayed the improved thermal stability. The high char yields of PVCIN nanocomposites also suggest improved flame retardence. It is plausible to propose that the improvement in weight retention is ascribed to the POSS constituent, which participated in the formation of the homogeneous hybrid network.