Oligomeric Silsesquioxane Nanocomposites Research Articles

Study on different behaviour of poly(vinylidene fluoride)-polyhedral oligomeric silsesquioxane nanocomposites in mechanical properties and nano-tensile testing

Nanocomposites consisting of a poly(vinylidene fluoride) (PVDF) matrix and 0, 3, 5 and 8 wt-% fluoropropyl polyhedral oligomeric silsesquioxane (FP-POSS) were prepared using the solvent evaporation method. The mechanical properties of nanocomposites were investigated by universal mechanical testing and nano-tensile testing. The results derived from two different scales testing both indicated that a small addition of FP-POSS exhibited a positive reinforcement effect of mechanical properties. Meanwhile the reason of the different variation trend of mechanical properties derived from testing standards under different scales was analysed, and the specific role and multi-performance of POSS were estimated.

Influence of the functionality of polyhedral oligomeric silsesquioxane–POSS containing glycidyl groups on the dispersion and interaction with epoxy nanocomposites

For the polyhedral oligomeric silsesquioxane (POSS) nanocomposites with epoxy resins, the POSS functionality is an important issue since these compounds will be diluted in the resin that will later undergo a chemical reticulation process. In this study, mono, tri and octa‐functional POSS containing glycidyl groups were dispersed in an epoxy resin by applying ultrasound. Based on the results obtained from the transmission electron microscopy, POSS tended to form an ordered phase to minimize the interfacial tension; however, this form was influenced by its functionality. The use of mono‐functional POSS shows finer dispersion and promotes an increase in the resin glass transition temperature. However, the octa‐functional POSS leads to improvement in thermal stability as seen in the degradation analysis. These results showed that the equilibrium of the dispersed nanoparticle is more evident for lower functionalized particles since higher functionalized ones hinder diffusion movements which ultimately form an ordered and dispersed phase in the resin during reticulation. POLYM. COMPOS., 38:E229–E236, 2017. © 2016 Society of Plastics Engineers

Electrochemical synthesis of polypyrrole/polyhedral oligomeric silsesquioxane nanocomposite on copper for corrosion protection

Abstract Electrochemical synthesis of polypyrrole (PPy)/polyhedral oligomeric silsesquioxane (POSS) nanocomposite on copper is studied using cyclic voltammetry technique in aqueous sodium benzoate solution. The resulting PPy/Cu and PPy/POSS/Cu films were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analysis. The performance of PPy and PPy/POSS nanocomposite as protective coatings against corrosion of Cu in 3.5% NaCl solution is assessed by potentiodynamic polarization technique and electrochemical impedance spectroscopy (EIS). The corrosion potential for PPy/POSS/Cu is positively shifts by 0.071 V in comparison with uncoated copper. The corrosion current density is found to be 24.08, 7.23, and 2.101 μA/cm2 for uncoated Cu, PPy coated Cu and PPy/POSS coated Cu, respectively. The results showed that by adding the POSS nanostructures within PPy matrix, the current density of the monomer oxidation decreased, significantly. The EIS studies indicated that the charge transfer resistance increases with the presence of PPy/POSS and accordingly, protection of copper improved against corrosion action.

Phase structure and mechanical properties of disentangled ultra-high molecular weight polyethylene/polyhedral oligomeric silsesquioxane nanocomposites in a solid state

Ultra-high molecular weight polyethylene (UHMWPE)/disilanolisobutyl polyhedral oligomeric silsesquioxane (POSS) nanocomposites in a disentangled state were synthesized by in situ ethylene polymerization. This is the first report of a detailed study on the phase structure and mechanical properties of disentangled UHMWPE/ POSS nanocomposites in a solid state. The phase structure and chain dynamics of UHMWPE nanocomposites were characterized using wide-line proton NMR and 13C cross-polarization/magic-angle spinning (CP/MAS) solid-state nuclear magnetic resonance (NMR). The results showed that a strong interaction between the POSS and nascent UHMWPE matrix occurred in a solid state, especially in the intermediate and monoclinic crystalline phases. This strong interaction between POSS particles and UHMWPE chains may result in improved melt recovery properties. Mechanical testing indicated that the lowest friction coefficients and highest breaking strength were achieved when 1 wt% loading of POSS was incorporated. The influence of the microstructure on lubrication and mechanical properties was also studied.

The microstructure of polyamide 6 and polyamide 6/polyhedral oligomeric silsesquioxane nanocomposites synthesized by phase inversion procedure under electric field

Polyamide 6 (PA6) and PA6/octaammonium POSS (OA-POSS) nanocomposites were synthesized by phase inversion procedure assisted with external electric field and characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and water contact angle (CA) measurements. It is very interesting to find that external electric field has greatly different effects on the microstructure evolution behaviors of PA6 and PA6/OA-POSS nanocomposites. For pure PA6 samples, crystallization was retarded while hydrophilicity was enhanced with increasing the strength of applied electric field. However, for PA6/OA-POSS nanocomposites, both crystallinity and hydrophilicity keep stable with increased electric field strength. The migration behavior of OA-POSS molecules was hindered under electric field. The mechanism for the formation of PA6 and PA6/OA-POSS nanocomposites with the presence of external electric field is discussed.

Crystallization and mechanical properties of biodegradable poly(p-dioxanone)/octamethyl-polyhedral oligomeric silsesquioxanes nanocomposites via simple solution casting method

In this study, biodegradable poly(p-dioxanone) (PPDO)/octamethyl-polyhedral oligomeric silsesquioxanes (ome-POSS) nanocomposites were fabricated by the simple solution casting method with various ome-POSS loadings. Scanning electron microscopic observations indicate that ome-POSS is well dispersed in the PPDO matrix. Effect of ome-POSS on the isothermal melt crystallization and dynamic mechanical properties of PPDO in the nanocomposites were studied in detail. It shows that the overall crystallization rates are faster in the nanocomposites than in neat PPDO and increase with the increase in ome-POSS loadings; however, X-ray diffraction patterns, POM and the Avrami exponent suggest that the crystal structure and the crystallization mechanism do not change despite the presence of ome-POSS. The mechanical property of PPDO/ome-POSS nanocomposites was enhanced with respect to neat PPDO.

Solvothermal synthesis of hydrophobic chitin–polyhedral oligomeric silsesquioxane (POSS) nanocomposites

Chitinous scaffolds isolated from the skeleton of marine sponge Aplysina cauliformis were used as a template for the deposition of polyhedral oligomeric silsesquioxanes (POSS). These chitin–POSS based composites with hydrophobic properties were prepared for the first time using solvothermal synthesis (pH 3, temp 80°C), and were thoroughly characterized. The resulting material was studied using scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and thermogravimetry. A mechanism for the chitin-POSS interaction after exposure to these solvothermal conditions is proposed and discussed.

Hybrid cationic ring-opening polymerization of epoxy resin/glycidyloxypropyl-polyhedral oligomeric silsesquioxane nanocomposites and dynamic mechanical properties

Glycidyloxypropyl-polyhedral oligomeric silsesquioxanes (G-POSS) were prepared from 3-glycidyloxypropyl-trimethoxysilane (GTMS) by hydrolytic condensation. The hybrid cationic thermal polymerization of G-POSS with bisphenol A epoxy resin (E-51) using diphenyliodonium fluoride borate (DPI·BF4) as a cationic initiator and benzoyl peroxide (BPO) as a co-initiator was investigated by DSC and FTIR. The structure of G-POSS was characterized by liquid chromatography–mass spectrometry (LC/MSD), FTIR and NMR. The effect of BPO content on reaction system, the distribution of G-POSS in the curing system, curing reaction activation energy Ea and dynamic mechanical properties of the E51/G-POSS nanocomposites were characterized. The results showed that octa(3-glycidyloxypropyl)-POSS (G-POSS) had been synthesized and displayed uniform dispersion in E51/G-POSS curing system. The DPI·BF4, which was capable to initiate the thermal ring-opening curing of epoxy resin, showed an initial curing temperature of epoxy resin decreased by 54.7 °C when the added amount of BPO was 2 wt%. The reaction process was well accorded with Kissinger’s kinetics model, and the average curing reaction activation energy Ea was increased as the content of G-POSS increased. The Tg and storage modulus of the E-51/G-POSS nanocomposites reached its optimum when the content of G-POSS was 2 wt%. The Tg of nanocomposite was 8.3 °C higher than that of the pure epoxy resin. The Tg and storage modulus decreased with the further increasing of G-POSS content.

Molecular Dynamics Simulations and Hygrothermal Aging of Polyurea–POSS Nanocomposites

The long-term performance of any novel material in its working environment is an intriguing area of research. The combined effect of the moisture content (relative humidity) and temperature of the environment degrades the mechanical properties of polymer composites. In the first part of this manuscript, polyurea–polyhedral oligomeric silsesquioxane (POSS) nanocomposites are subjected to continuous hygrothermal cycling. The effects of prolonged hygrothermal aging on the mechanical performance of the composites are evaluated in terms of the change in tensile strength and elongation at failure. Aged composites are subjected to FTIR spectroscopy to study the chemical changes resulting from the hydrolysis of polyurea. In the second part, attempts are made to study the effect of the addition of POSS nanoreinforcement on the mechanical properties of the resulting composite materials using molecular dynamics (MD) simulations. Results obtained here show poor agreement between MD simulation results and results obtained using dynamic mechanical analysis studies. However, qualitatively, both simulation and experimental results exhibit similar effects due to addition of POSS nanoparticles on the mechanical properties of polyurea–POSS nanocomposites.

Synthesis, Characterization and Gas Transport Properties of Polyamide-Tethered Polyhedral Oligomeric Silsesquioxane (POSS) Nanocomposites

Polyamide-tethered polyhedral oligosilsesquioxane (POSS) nanocomposites (PAMIP) with well-defined architectures have been synthesized through Michael addition reaction between the maleimide-containing fluorinated new copolyamides (PAMI) with amino-functionalized POSS (POSS-NH2) nanofiller. The chemical structures of the polyamide–POSS nanocomposites were characterized by 1H NMR and Fourier transform infrared spectroscopy. The effects of POSS-NH2 on the morphology and properties of the PAMIP membranes were examined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction and transmission electron microscopy (TEM) analysis. POSS molecules tethered to polyamide form sphere shaped POSS aggregate cages (phase separated morphology) were confirmed by TEM analysis. All the PAMIP membranes showed very high permeability for different gases compared to PAMI membranes. The increase in permeability is accompanied by increase in diffusivity coefficient of the PAMIP membranes for d...

Synthesis, structure, and properties of high‐impact polystyrene/octavinyl polyhedral oligomeric silsesquioxane nanocomposites

The organic–inorganic hybrid nanocomposites from high‐impact polystyrene/octavinyl polyhedral oligomeric silsesquioxane (HIPS/POSS) containing various percentages of POSS were prepared by free radical polymerization and characterized by Fourier transform infrared spectroscopy (FTIR), 1H‐NMR, thermal gravity analysis (TGA), X‐ray diffraction (XRD), and transmission electron microscopy (TEM). The octavinyl POSS has formed covalent bond connected PS‐POSS hybrid with polystyrene. POSS can well disperse in the composites at the composition of 0.5 and 1 wt%. The mechanical properties and thermostability of HIPS/POSS nanocomposites were significantly improved. The tensile strength, the izod impact strength, and the elongation at break of the nanocomposite containing 1 wt% of POSS was increased, respectively, by 15.73%, 75.62%, and 72.71% in comparison with pristine HIPS. The thermal decomposition temperature of HIPS/POSS (1 wt% of POSS) was 33°C higher than that of pristine HIPS. The HIPS/POSS nanocomposites showed great potential for applications in many fields, such as electric appliance and automotive trim. POLYM. COMPOS. 37:1049–1055, 2016. © 2014 Society of Plastics Engineers

Thermal and dielectric properties of newly developed linear aliphatic-ether linked bismaleimide-polyhedral oligomeric silsesquioxane (POSS-AEBMI) nanocomposites

A new series of four different linear aliphatic ether linked aromatic bismaleimides (AEBMIs) were synthesized from the respective linear aliphatic ether-linked aromatic diamines and maleic anhydride. Further, the POSS-AEBMI nanocomposites were developed by Michael addition reaction of bismaleimide with varying mass percentages of octa(aminophenyl)silsesquioxane and were characterized by the fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. Data from thermal studies revealed that the POSS-reinforced AEBMI nanocomposites possesses higher glass transition temperature (Tg), thermal stability, limiting oxygen index, and lower dielectric constant when compare to that of neat AEBMI. X-ray diffraction and transmission electron microscopy analysis confirmed the molecular level dispersion of POSS in the AEBMI matrix.

Isothermal Cold Crystallization and Melting Behaviors of Poly(lactic acid)/Epoxy Vinyl Polyhedral Oligomeric Silsesquioxanes Nanocomposites

Poly(l-lactic acid) (PLA)/epoxy vinyl polyhedral oligomeric silsesquioxane (EP-POSS) nanocomposites were prepared via melt blending. The isothermal cold crystallization and melting behavors of pure PLA and its nanocomposites were investigated using differential scanning calorimetry (DSC). The crystal growth model of PLA was a mixture of two-dimensional discotic growth and three-dimensional spherulite growth, as evidenced by the values of the Avrami exponent ranging from 2.15 to 2.66. The crystallization rate displayed a great dependence on the EP-POSS loading level and crystallization temperature, and a transition from regime II to regime III was observed around 115°C. The values of fold surface free energy were calculated from the nucleation parameter which was determined by the Hoffman-Lauritzen equation. Polarizing microscope images (POM) indicated that EP-POSS promoted the nucleation of PLA.

Crystallization behavior of ultrahigh‐molecular‐weight polyethylene/polyhedral oligomeric silsesquioxane nanocomposites prepared by ethylene in situ polymerization

ABSTRACTA [3‐t‐Bu‐2‐OC6H3CHN(C6F5)]2TiCl2 catalyst (bis(phenoxyimine)titanium dichloride complex – FI catalyst) was immobilized on disilanolisobutyl polyhedral oligomeric silsesquioxane (OH‐POSS) to prepare ultrahigh molecular‐weight polyethylene (UHMWPE)/polyhedral oligomeric silsesquioxane (POSS) nanocomposites during ethylene in situ polymerization. The dispersion state of POSS in the UHMWPE matrix was characterized by X‐ray diffraction measurements and transmission electron microscopy. It was shown that the OH‐POSS achieved uniformed dispersion in the UHMWPE matrix, although its polarity was unmatched. The isothermal and nonisothermal crystallization behavior of the nanocomposites was investigated by means of differential scanning calorimetry. The crystallization rate of the nanocomposites was enhanced because of the incorporation of POSS during the isothermal crystallization. POSS acted as a nucleus for the initial nucleation and the subsequent growth of the crystallites. For nonisothermal studies, POSS showed an increase in the crystallinity. The crystallization rate of the nanocomposites decreased because the presence of POSS hindered the crystal growth. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40847.

Electrospinning of poly(lactic acid)/polyhedral oligomeric silsesquioxane nanocomposites and their potential in chondrogenic tissue regeneration

The study was conducted to evaluate the cytocompatibility and hydrolytic degradability of the new poly(lactic acid)/polyethylene glycol-polyhedral oligomeric silsesquioxane (peg-POSS/PLLA) nanocomposite as potential material for cartilage regeneration. PLLA scaffolds containing 0 to 5% of peg-POSS were fabricated by electrospinning. Human mesenchymal stem cells (hMSC’s) were cultured in vitro to evaluate the cytocompatibility of the new nanocomposite material. Hydrolytic degradation studies were also carried out to analyze the mass loss rate of the nanocomposites through time. The addition of the peg-POSS to the PLLA did not affect the processability of the nanocomposite by electrospinning. It was also observed that peg-POSS did not show any relevant change in fibers morphology, concluding that it was well dispersed. However, addition of peg-POSS caused noticeable decrease in mean fiber diameter, which made the specific surface area of the scaffold to rise. hMSC’s were able to attach, to proliferate, and to differentiate into chondrocytes in a similar way onto the different types of electrospun peg-POSS/PLLA and pure PLLA scaffolds, showing that the peg-POSS as nano-additive does not exhibit any cytotoxicity. The hydrolytic degradation rate of the material was lower when peg-POSS was added, showing a higher durability of the nanocomposites through time. Results demonstrate that the addition of peg-POSS to the PLLA scaffolds does not affect its cytocompatibility to obtain hyaline cartilage from hMSC’s.

Preparation of flexible PLA/PEG-POSS nanocomposites by melt blending and radiation crosslinking

In this study, poly(lactic acid) (PLA)/poly(ethylene glycol)-functionalized polyhedral oligomeric silsesquioxane (PEG-POSS) nanocomposites with or without triallyl isocyanurate (TAIC) were investigated by melt blending and electron beam irradiation to enhance the flexibility of PLA. Based on the results of the crosslinking degree measurements, the PLA/PEG-POSS nanocomposites were crosslinked by electron beam irradiation in the presence of triallyl isocyanurate (TAIC) and their crosslinking degree reached up to 80% based on the absorbed dose and their compositions. From the results of the FE-SEM and EDX Si-mapping, the crosslinked PLA/PEG-POSS nanocomposites were homogenous without a micro-phase separation or radiation-induced morphological change. Based on the results of the tensile test, the PLA/PEG-POSS nanocomposites containing 15wt% PEG-POSS exhibited the highest flexibility, and their tensile strength showed a maximum value of 44.5MPa after electron beam irradiation at an absorbed dose of 100kGy in the presence of TAIC, which is comparable to non-biodegradable polypropylene. The results of the dynamic mechanical analysis revealed that the crosslinked PLA/PEG-POSS nanocomposites exhibited a higher thermal resistance above their melting temperature in comparison to that of the neat PLA, although their glass transition temperature was lower than that of the neat PLA. The enzymatic biodegradation test revealed that the PLA/PEG-POSS nanocomposites were biodegradable even though their biodegradability was deteriorated in comparison to that of the neat PLA.

Hybrid organic–inorganic nanocomposite: Fluorinated poly-(2,5-thienylbenzobisoxazole)/POSS and its properties

This article reports the in situ preparation of fluorinated poly-(2,5-thienylbenzobisoxazole)/polyhedral oligomeric silsesquioxane (6FPBOT/POSS) nanocomposites and their chemical and physical properties. POSS participated in the polymerization reaction and thus led to the homogenous dispersion of POSS nanoparticles in the 6FPBOT matrix. The structures and morphology of the obtained nanocomposites were fully characterized by Fourier transform infrared spectroscopy, wide-angle X-ray scattering, thermogravimetric analysis, and transmission electron microscopy. The nanocomposites exhibited excellent thermal stability. The introduction of POSS evidently increased the mechanical properties (tensile strength and tensile modulus) of the nanocomposites and significantly enhanced the quantum yield of 6FPBOT by reducing the degree of interchain aggregation. The dielectric constants of the nanocomposites decreased with increasing POSS content. The dielectric constant of the materials decreased from 2.56 for the 6FPBOT to 2.11 for the 6FPBOT–POSS nanocomposite with 5% POSS.

Synthesis and characterization of UV-cured epoxy acrylate/POSS nanocomposites

In this study, epoxy acrylate (EA)/vinyl-polyhedral oligomeric silsesquioxane (POSS) nanocomposites were prepared through in situ polymerization and by UV-curing technique. The vinyl-POSS monomers were added to EA matrix by physically blending at loadings between 0wt.% and 15wt.%. The microstructure of the EA/vinyl-POSS composites was studied by X-ray diffraction (XRD) measurements, and the result indicated that the separate POSS domains were present in EA/POSS composites. Aggregates were observed in the nanocomposites by SEM and the EDS results indicated that there were vinyl-POSS molecules existing in the EA matrix. TEM images further proved there were both POSS aggregates and monomers dispersed in the EA matrix. The kinetics of the photopolymerization was investigated by real time FTIR spectroscopy. The DSC analysis showed that the increasing POSS content caused a decrease on the composite's glass transition temperature. TGA measures confirmed that the degradation mechanism of EA was not affected by POSS and the nanocomposites thermal stability was slightly improved with the increasing of POSS loadings. It can be seen that the degradation rate slowed down with the increasing of POSS content and the 50% mass loss temperature of EA/POSS hybrids all increased conspicuously relative to plain EA.

Non-isothermal crystallization kinetics of polypropylene/MAP-POSS nanocomposites

Non-isothermal crystallization kinetics of polypropylene (PP)/methylacryloypropy polyhedral oligomeric silsesquioxanes (MAP-POSS) nanocomposites (PP/MAP-POSS) were investigated by DSC at various cooling rates. Jeziorny and Mo method were used to study the non-isothermal crystallization kinetics. The results show that the Jeziorny and Mo method are all successful in describing the non-isothermal crystallization kinetics of PP/MAP-POSS nanocomposites. The MAP-POSS can act a role of heterogeneous nucleation and increase the crystallization rate constant Z c and decrease crystallization half time t 1/2, and the spherulite crystal size decreases, the inter-spherulitic action or crosslinking structure each other appear at the appropriate content. The DSC peak temperature T p increase about 5 °C, t 1/2 reduce 0.21 min at 6 % content of MAP-POSS and heating rate of 10 °C/min. The MAP-POSS can also increase the mechanical property of PP/MAP-POSS nanocomposites, the tensile strength and impact strength increase from 12.97 to 19.93 MPa and from 33.2 to 52.6 kJ/m2, respectively, at 4 % content of MAP-POSS. But the spherulitic crystal becomes larger and boundaries become clearer again; the macrophase separation will occur and mechanical properties decrease when more and more MAP-POSS was added. The nanocomposite has the best mechanical property at 4 % content of MAP-POSS.

Thermal and Mechanical Properties of Hydroxyl-Terminated Polybutadiene-Based Polyurethane/Polyhedral Oligomeric Silsesquioxane Nanocomposites Plasticized with DOA

Thermal and mechanical properties of PU/POSS nanocomposites plasticized with DOA were investigated. These hybrid materials were prepared using one-step method through the incorporation of flexible HTPB prepolymer, reactive or non-reactive POSS nanoparticle, and DOA plasticizer under IPDI curative system. The plasticizer added into PU/POSS composites decreased glass transition temperature, mechanical strength and modulus, while the change of thermal stability was modest. Thermal stability of these hybrid composites was found to depend preferably on characteristics of POSS molecules incorporated.