Epoxy/silsesquioxane organic–inorganic hybrids: Sol–gel synthesis of inorganic precursors containing amino and phenyl groups

The synthesis of silsesquioxane oligomers containing amino and phenyl groups by sol–gel process and the formation of an organic–inorganic hybrid, by the reaction of amino groups of the silsesquioxane precursor with epoxy rings of diglycidyl ether of bisphenol A, have been investigated. Acid catalysis proved to be more efficient than basic catalysis for the condensation reaction between 3‐aminopropyltriethoxysilane (APES) and phenyltriethoxysilane (PETS) in ethanol. Liquid state ²⁹Si nuclear magnetic resonance (²⁹Si NMR) analysis indicated that T³ structures are the major phase forming the network structure. Infrared spectroscopy analyses confirmed the formation of the epoxy/silsesquioxane hybrid and showed that a high degree of cure was achieved. A distinct behavior of the glass transition temperature (T_g) between the hybrids cured at different time intervals after the chemical modification was observed, and the most significant value was an increase of 13°C in T_g obtained with the hybrid produced with silsesquioxane oligomers synthesized by sol–gel for 18 h. From thermogravimetric analyses (TGAs), it was observed an increase on the residual masses for the hybrids and a decrease in their degradation rates, suggesting an improvement of thermal stability. These results indicate the formation of a new organic–inorganic hybrid material with potential applications for high performance coatings and structural components. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Thermal conductivity and thermal properties of POSS/polytriazole organic–inorganic hybrid material

To decrease the thermal conductivity of polytriazole‐based fiber reinforced composites, an organic–inorganic POSS/polytriazole hybrid resin was obtained. The influences of various proportions of POSS on thermal conductivity and the thermal properties of hybrid materials were emphatically investigated. The results show that POSS incorporation resulted in not only decreased thermal conductivity but also increased T_g and thermal decomposition temperature. The enhancement was ascribed to the nanoscale effect of POSS structure and the fact that the POSS framework has a high heat resistance property. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41967.     

Bioactive and degradable organic–inorganic hybrids

CaO–SiO₂–poly(vinyl alcohol) (PVAL) and CaO–P₂O₅–SiO₂–PVAL organic–inorganic hybrids were obtained as monoliths and characterized before and after be soaked in a solution mimicking human plasma. The hybrids were obtained by adding PVAL (0.9, 1.8 and 3.6 wt.%) to three CaO–(P₂O₅)–SiO₂ gel glasses with 25 mol% of CaO and 0, 2.5 and 5 mol%, respectively of P₂O₅. The influence of PVAL and P₂O₅ on the monoliths obtaining and on their textural properties and in vitro behavior was analyzed. Additions of PVAL favored the synthesis of cracked-free monoliths able to be coated with bone-like apatite after be soaked in Kokubo's simulated body fluid (SBF), i.e. to present in vitro bioactivity. Increasing P₂O₅ contents made the hybrids syntheses difficult and decreased their in vitro bioactivity. In addition, the in vitro degradation of hybrids increased with the increasing of PVAL and P₂O₅. Thus, hybrids with the highest amounts of both components showed so high degradation in SBF that the apatite layer formation was impeded. Organic–inorganic hybrids in these systems could be clinically used as bone defect fillers in non load bearing applications or as matrices in controlled release systems.     

New polyimide–silica organic–inorganic hybrids

A series of polyimide–silica hybrid films with silica contents up to 30 wt % were successfully prepared by the sol‐gel reaction of tetraethoxysiliane in the presence of poly(amic acid) containing pendent hydroxyl groups. The films were yellow and transparent when the silica content was less than 11 wt %. The chemical structure of the films was characterized by Fourier transform infrared spectroscopy, and the morphology of the films was investigated by scanning electronic microscopy and atomic force microscopy. Thermogravimetric analysis, differential scanning calorimetry, and stress–strain tests were used to measure the performance of the films. The results indicate that the glass‐transition temperatures and decomposition temperatures of the hybrid films increased with increasing silica content, whereas the tensile strength had a maximum with the variety of silica contents. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2210–2214, 2003     

Glass‐polymer melt hybrids. I: Viscoelastic properties of novel affordable organic‐inorganic polymer hybrids

A novel class of organic‐inorganic polymer hybrids was developed by melt‐blending up to 50 (v/v) % [about 83 (w/w) %] tin‐based polyphosphate glass (Pglass) and low‐density polyethylene (LDPE) in conventional plastics processing equipment. The liquid‐ and solid‐state rheology of the polymer hybrids was studied under oscillatory shear flow and deformation to understand the behavior of these materials and to accelerate efforts to melt process the Pglass with organic polymers. All the materials were found to be linearly viscoelastic in the range of temperature and frequencies examined and their viscoelastic functions increased with increasing Pglass concentration. The Pglass significantly enhanced the shear‐thinning characteristics of the Pglass‐LDPE hybrid, indicating the presence of nonlinear chemical and physical interactions between the hybrid components. Morphological examination of the materials by scanning electron microscopy revealed interesting evolution of microstructure of the Pglass phase from droplets (or round beads) to elongated and interpenetrating network structures as the glass concentration was increased in the Pglass‐LDPE hybrids. Melt viscosities of the materials were well described by a simple power‐law equation and a Maxwellian (Hookean) model with three relaxation times. Time‐temperature superpositioning (TTS) of the complex viscosity versus frequency data was excellent at 170°C < T < 220°C and the temperature dependencies of the shift factors conformed excellently well to predictions from an Arrhenius‐type relation, enabling calculation of the flow‐activation energies (25–285 kj/mol) for the materials. The beneficial function of the Pglass in the hybrid system was significantly enhanced by pre‐treating the glass with coupling agents prior to incorporating them into the Pglass‐LDPE hybrids.     

Morphologies and mechanical properties of organic–inorganic multilayered composites

Organic–inorganic composites have received increasing attention because such composites exhibit improved optical, electrical, thermal, and mechanical behaviors by combining properties of both organic polymers and inorganic compounds. However, tensile strength is enhanced generally at the cost of decreasing ductility, which is not suitable for biomedical applications where tissue‐like elasticity is required. In this study, multilayered poly(vinyl alcohol) (PVA)/silica composites were synthesized, which achieved a significant enhancement in tensile strength and ductility. The chemical structure, thermal stability, and fracture morphologies of multilayered films were investigated to analyze the reinforcement mechanism. The results showed that extensive plastic tearing took place in monolayered composites with low‐silica contents and in all multilayered ones, whereas the monolayered composites with high‐silica contents were dominated by brittle fracture. For layered composite with 30 wt% silica in the second layer, the elongation at break is 237.8%, which is 3.21 times that of monolayered 30% SiO₂/PVA 74.0%. Also its tensile strength is 37.8 MPa, which is 1.52 times that of monolayered 30% SiO₂/PVA 24.8 MPa. These improved mechanical properties broaden its potential application, especially the applications of PVA in medical materials, which are intensely discussed as biomaterials. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Epoxy‐functionalized polyhedral oligomeric silsesquioxane/cyanate ester resin organic–inorganic hybrids with enhanced mechanical and thermal properties

A series of cyanate ester resin (CE) based organic–inorganic hybrids containing different contents (0, 5, 10, 15 and 20 wt%) of epoxy‐functionalized polyhedral oligomeric silsesquioxane (POSS‐Ep) were prepared by casting and curing. The hybrid resin systems were studied by the gel time test to evaluate the effect of POSS‐Ep on the curing reactivity of CE. The impact and flexural strengths of the hybrids were investigated. The micromorphological, dynamic mechanical and thermal properties of the hybrids were studied by SEM, dynamic mechanical analysis (DMA) and TGA, respectively. Results showed that POSS‐Ep prolonged the gel time of CE. CE10 containing 10 wt% POSS‐Ep displayed not only the optimum impact strength but the optimum flexural strength. SEM results revealed that the improvement of mechanical properties was attributed to the large amount of tough whirls and fiber‐like pull‐outs observed on the fracture surfaces of CE10. DMA results indicated that POSS‐CE tended to decrease E′ of the hybrids in the glassy state but to increase E′ of the hybrids in the rubbery state. TGA results showed that CE10 also possesses the best thermal stability. The initial temperature of decomposition (T_i) of CE10 is 426 °C, 44 °C higher than that of pristine CE. © 2013 Society of Chemical Industry     

Novel organic–inorganic hybrid coatings prepared by the sol–gel process: corrosion and mechanical properties

(Hyperbranched polyurethane‐urea)/[(3‐aminopropyl)triethoxysilane]‐ZnO (HBPUU‐APTES‐ZnO) hybrid coatings were synthesized using an inexpensive mixing technique by varying the APTES‐modified ZnO concentration. The mechanical and surface properties of the hybrid coating films were studied and compared with unmodified and modified ZnO. The corrosion, solvent and abrasion resistance show significant enhancement in HBPUU‐APTES‐ZnO hybrids and their properties are increased with increasing APTES‐ZnO concentration. This hybrid coating has opened up an opportunity for automotive topcoat application. Copyright © 2012 Society of Chemical Industry     

Methyl silsesquioxane/cyanate ester resin organic–inorganic hybrids with low dielectric constant

A kind of nonfunctional oligomeric silsesquioxane (SSQ), methyl silsesquioxane (Me‐SSQ), was used to modify cyanate ester (CE) resin in this article. First, Me‐SSQ was synthesized by the hydrolysis and condensation of methyltriethoxysilane. Then, a series of Me‐SSQ/CE hybrids containing 0, 1, 5, 10, and 20 wt % of Me‐SSQ were prepared. The effect of Me‐SSQ content on the reactivity, mechanical, dielectric, thermal, and hot/wet properties of materials was investigated. Fourier transform infrared spectroscopy was used to study the reactivity of hybrid CE resin systems, indicating that the addition of Me‐SSQ does not show significant effect on the conversion of CE. Mechanical and dielectric properties of the Me‐SSQ/CE hybrid materials were also studied. Impact strength of the Me‐SSQ/CE hybrids reaches its maximum value when Me‐SSQ content is 5 wt %. However, the flexural strength reaches the maximum value when Me‐SSQ content is 1 wt %. The Me‐SSQ/CE hybrid containing 20 wt % of Me‐SSQ shows a dielectric constant of 2.78, that is, much lower than the pure CE resin. At the same time, the dielectric loss of the Me‐SSQ/CE hybrids was slightly increased (tan δ < 0.006). Therefore, Me‐SSQ/CE hybrid is a promising candidate for high‐performance printed circuit board matrix materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Electrical behavior of PET films coated with nanostructured organic–inorganic hybrids

Hybrid coatings, based on poly(ethylene oxide) (PEO) or polycaprolactone (PCL) and silica (SiO₂), at different organic–inorganic compositions have been used to coat PET films employed in the electric industry to produce capacitors. The overall electrical behavior of the coated films has been investigated. The electrical strength of the coated films increases up to 10–15% of the uncoated ones regardless of polymer type (PEO/PCL) and amount of inorganic phase, as far as the thickness of the coating is below 5 μm. A systematic increase of surface electrical conductivity is found in all coated samples which however still behave as insulators. Permittivity and loss factor also increase particularly at low frequencies (< 10 Hz) on account of the presence of ions deriving from the sol–gel process and on the presence of interfacial polarization probably related to the coatings nanostructurated morphology which leads to phase separation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4870–4877, 2006     

Synthesis,Morphology and Viscoelastic Properties of Epoxy/Polyhedral Oligomeric Silsesquioxane (POSS) and Epoxy/Cyanate Ester/POSS Nanocomposites

TriSilanolPhenyl-polyhedral oligomeric silsesquioxane (POSS-1) (C₄₂H₃₈O₁₂Si₇), 1–15 wt%, was incorporated into aliphatic epoxy resin (Clearstrem Products, Inc.) with aliphatic diamine curing agents and cured. This epoxy resin was also blended with an equal weight (50/50 w/w) of aromatic cyanate ester resin, Lonza’s PT-15, and 1–15 wt% of POSS-1 and cured. These composites were characterized by FT-IR, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (X-EDS), dynamic mechanical thermal analysis (DMTA) and three-point bending flexural tests. XRD and X-EDS measurements were consistant with partial molecular dispersion of the POSS units in the continuous matrix phase, together with POSS aggregates. TEM and SEM show that POSS-1-enriched nanoparticles are present in the matrix resins of both the epoxy/POSS and epoxy/cyanate ester/POSS-1 composites. The storage bending moduli, E′, in the rubbery region and the glass transition temperatures, T_g, of epoxy and epoxy/cyanate ester 1-5% POSS-1 composites are higher than those of the reference resins. Small amounts (≤5 wt%) of POSS-1 improved E′ and T_g of both systems and raised flexural strengths and moduli.     

Dynamic rheological behavior and mechanical properties of PVC/CPE/MAP–POSS nanocomposites

Poly(vinyl chloride)/chlorinated polyethylene (PVC/CPE)/methylacryloylpropyl‐containing polyhedral oligomeric silsesquioxane (MAP–POSS) nanocomposites are prepared. The plastic behavior and dynamic rheological behavior of PVC/CPE/MAP–POSS are investigated. The influences of composition on dynamic storage modulus G′, loss modulus G″, and complex viscosity η* of PVC/CPE/MAP–POSS melts are discussed. The dynamic mechanical properties, mechanical properties, and morphology are determined. The results show that both plastic time and balance torque of the nanocomposites decrease, but the G′, G″, and η* all increase with increasing MAP–POSS content. The maximum value of the dynamic mechanical loss tan δ decreases and elasticity increases when MAP–POSS is added. The impact strength of the nanocomposites increases with increasing MAP–POSS content and has the best value at 10% content of MAP–POSS, which is 5.38 kJ/m² higher than that of the blend without MAP–POSS. The MAP–POSS can be used as an efficient process aid and impact aid for the PVC/CPE blend. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and properties of PMMA‐ZrO2 organic–inorganic hybrid films

In this work we report the synthesis process and properties of PMMA‐ZrO₂ organic–inorganic hybrid films. The hybrid films were deposited by a modified sol‐gel process using zirconium propoxide (ZP) as the inorganic (zirconia) source, methyl methacrylate (MMA) as the organic source, and 3‐trimetoxy‐silyl‐propyl‐methacrylate (TMSPM) as the coupling agent between organic and inorganic phases. The films were deposited by dip coating on glass slide substrates from a hybrid precursor solution containing the three precursors with molar ratio 1 : 0.25 : 0.25 for ZP, TMSPM, and MMA, respectively. After deposition, the hybrid thin films were heat‐treated at 100°C for 24 h. The macroscopic characteristics of the hybrid films such as high homogeneity and high optical transparence evidenced the formation of a cross‐linked, interpenetrated organic–inorganic network. The deposited PMMA‐ZrO₂ hybrid films were homogeneous, highly transparent and very well adhered to substrates. Fourier Transform Infra‐Red measurements of the hybrid films display absorption bands of chemical groups associated with both PMMA and ZrO₂ phases. The amounts of organic and inorganic phases in the hybrid films were determined from thermogravimetric measurements. The surface morphology and homogeneity of the hybrid films at microscopic level were analyzed by scanning electron microscopy and atomic force microscopy images. From the analysis of optical transmission and reflection spectra, the optical constants (refraction index and extinction coefficient) of the hybrid films were determined, employing a physical model to simulate the hybrid optical layers. The refraction index of the hybrid films at 532 nm was 1.56. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42738.     

Synthesis and characterization of organic–inorganic hybrids based on epoxy resin and 3‐glycidyloxypropyltrimethoxysilane

Organic–inorganic hybrid materials based on diglycidyl ether of bisphenol A (DGEBA) and 3‐glycidyloxypropyltrimethoxysilane (GLYMO) were prepared, using a poly(oxypropylene) diamine Jeffamine D230 as a curing agent. Materials were studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), infrared spectroscopy, swelling in tetrahydrofurane (THF), and Soxhlet extraction in THF. A dependence of the final conversion of epoxy groups and the final degree of organic phase crosslinking on inorganic phase content was found. The inorganic phase presents a steric hindrance to full crosslinking of epoxy groups. It also immobilizes the organic chains and improves the temperature stability of hybrid materials. Products of GLYMO hydrolysis together with unreacted organic molecules lower the glass transition temperature of hybrid materials. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 498–505, 2004     

Creep and recovery behavior of novel organic‐inorganic polymer hybrids

A novel class of organic‐inorganic polymer hybrids were developed by meltblending up to 50 (v/v) % [about 83 (w/w) %] tin‐based polyphosphate glass (Pglass) and low‐density polyethylene (LDPE) in conventional plastics processing equipment. The creep and recovery behavior of these polymer hybrids at 30°C were studied to understand the effect of the Pglass on the creep resistance of the LDPE. The results suggest that the Pglass acts as a reinforcement and an increase in the Pglass loading leads to significantly lower creep strains. This creep resistance is further enhanced by pretreating the Pglass with coupling agents prior to incorporating them into the Pglass‐LDPE hybrids. The experimental creep compliance of these materials conformed excellently with empirical power‐law equation and a modified Burger's model, suggesting that the materials are linearly viscoelastic under the test conditions.     

Nanocomposite coatings via simultaneous organic–inorganic photo‐induced polymerization: synthesis,structural investigation and mechanical characterization

Hybrid sol–gel films were prepared via a simultaneous organic‐inorganic UV‐curing process using a diaryliodonium salt as a superacid photogenerator. In this single‐step procedure, an epoxy functionalized reactive resin mixed with a variable amount of either of two epoxy trialkoxysilane precursors was UV‐irradiated, causing both the initiation of epoxy ring‐opening copolymerization and the catalysis of trialkoxysilyl sol–gel reactions. The concomitant photo‐induced sol–gel process was found to have a significant effect on the two related propagation mechanisms in competition for the oxirane ring‐opening—the active chain‐end and the activated monomer mechanisms—as proved by a systematic examination of the hybrid material microstructure through ²⁹Si and ¹³C solid‐state NMR spectroscopy. The effect of the oxo‐silica network generation on the epoxy reaction kinetics was also evaluated using real‐time Fourier transform infrared spectroscopy upon varying the epoxysilane structure and its concentration. Thermal and dynamic mechanical analyses were systematically performed on these hybrids, by studying thoroughly their structure–property interdependence. Other mechanical characterizations through tribological and scratch tests suggested that the present photopolymer–silica hybrid material provides a powerful tool to tailor mechanical property profiles. Copyright © 2010 Society of Chemical Industry     

Polyimide/POSS nanocomposites: interfacial interaction, thermal properties and mechanical properties

A series of functional polyhedral oligomer silsesquioxnae (POSS)/polyimide (PI) nanocomposites were prepared using a two-step approach, first, the octa(aminophenyl)silsesquioxane (OAPS)/NMP solution was mixed with polyamic acid (PAA) solution prepared by reacting 4,4′-diaminodiphenylmethane and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride in NMP, and second, the polycondensation solution was treated by thermal imidization. The well-defined ‘hard particles’ (POSS) and the strong covalent bonds between the PI and the ‘hard particles’ lead to a significant improvement in the thermal mechanical properties of the resulting nanocomposites. The glass transition temperature dramatically increases while the coefficient of thermal expansion (CTE) decreases, owing to the significant increase of the cross-linking density in the PI-POSS nanocomposites. The thermal stability and mechanical property of the nanocomposites were also improved.     

Rubber-elasticity of hybrid organic–inorganic composites evaluated using dynamic mechanical spectroscopy and equilibrium swelling

Estimations of the average molar mass between crosslinks for sol-gel-derived poly(tetramethylene oxide) (PTMO)–polysilicate hybrid composites have been made using both dynamic tensile modulus and equilibrium swelling techniques. Modulus-based calculations have been performed using storage modulus values obtained from dynamic mechanical spectroscopy at frequencies ranging from 0.1 to 10 Hz. The analysis revealed that gels containing either 4 or 19% polysilicate (by volume) had an average molar mass between crosslinks significantly less than that predicted by a PTMO and SiO₂ rule of mixtures. Thus, the analysis indicates that there is extensive restriction of PTMO chain mobility in these gels. Aging of the 19% polysilicate-loaded gels in a basic ethylamine and water solution for 25 h, which has previously been shown to enhance phase separation without loss of optical transparency, results in increasing average chain length. To verify this approach, the values obtained using the dynamic mechanical spectroscopy-based technique were compared with those calculated using the Flory-Rehner equation. Somewhat surprisingly, the analyses by both techniques were in excellent agreement, thereby suggesting that, in the absence of chemical change, elementary rubber elasticity theory is a good tool for investigating the phase interactions in these seemingly nonideal hybrid composites. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 947–957, 1998     

Preparation and mechanical properties of polystyrene–clay hybrids

Polystyrene–clay hybrids (PSCHs) were prepared by melt blending a styrene vinyloxazoline copolymer with organophilic clay. In the PSCHs, the silicate layers of the clay were delaminated and dispersed homogeneously to the nanometer level. The moduli of the PSCHs were higher than that of the PS copolymer. For example, the tensile modulus of the PSCH with 5 wt % clay was 1.4 times higher compared to that of the PS copolymer. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3359–3364, 1999     

Formation of macroporous organic‐inorganic polymer hybrids using tea extract

Macroporous organic–inorganic polymer hybrids were prepared from poly(vinyl pyrrolidone), and inorganic alkoxides. To a reaction mixture of poly(vinyl pyrrolidone) and tetramethoxysilane, extract from tea leafs and HCl aqueous solution in methanol were added. The resulting mixture was constantly stirred at room temperature for 1 h and heated at 60°C for two weeks. Consequently, the corresponding polymer hybrid became a macroporous material having a pore size from 3.26 to 20.86 μm. We succeeded in finding that the pruned tea leafs were able to utilize the synthesis of novel macroporous materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011