In situ polymerization of silicic acid in polyethylene–octene elastomer: Properties and characterization of the hybrid nanocomposites

Silicic acid produced from sodium metasilicate hydrate and metallocene polyethylene–octene elastomer (POE) were chosen as the ceramic precursor and the continuous phase, respectively, for preparation of new hybrids by an in situ sol–gel process. To obtain a better hybrid, the acrylic acid‐grafted polyethylene–octene elastomer (POE‐g‐AA) prepared in our laboratory and used as the continuous phase was also investigated. Characterizations of POE/SiO₂ and POE‐g‐AA/SiO₂ composites were performed by Fourier transform infrared spectroscopy, ²⁹Si solid‐state nuclear magnetic resonance (NMR) spectrometry, X‐ray diffractometry, differential scanning calorimetry, thermogravimetry analysis, and an Instron mechanical tester. The POE‐g‐AA/SiO₂ hybrid could give the positive effect on the properties of POE/SiO₂ hybrid because the carboxylic acid groups of acrylic acid should act as coordination sites for the silica phase to form chemical bonds. The result of ²⁹Si solid‐state NMR spectra showed that Si atom coordination around SiO₄ units is predominantly Q₃ and Q₄. Also, the POE‐g‐AA/SiO₂ hybrid with 15 wt % SiO₂ gave the maximum values of tensile strength and glass‐transition temperature because excess particles might cause the separation between the organic and inorganic phases when the silica content was beyond this point. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 351–359, 2003     

Organic–inorganic polymeric nanocomposites involving novel titanium tetraisopropylate in polyethylene–octene elastomer

The new nanocomposites, by means of an in situ sol–gel process consisting of metallocene polyethylene–octene elastomer (POE) and titanium tetraisopropylate (TTIP), were investigated. In addition, the acrylic acid grafted POE (POE‐g‐AA) was studied as an alternative to POE. Fourier transform infrared (FTIR) spectroscopy, a dynamic mechanical analyzer (DMA) spectrometer, an X‐ray diffractometer (XRD), differential scanning calorimetry (DSC), a thermogravimetric analyzer (TGA), an Instron mechanical tester, and a scanning electron microscope (SEM) were used to characterize and examine the samples. The results indicate that the POE‐g‐AA/TiO₂ hybrid could have a positive effect on the properties of the POE/TiO₂ hybrid because the carboxylic acid groups of acrylic acid should act as coordination sites for the titania phase to form a Ti? O? C chemical bond. The strength of interfacial bonding between the polymer chains and the ceramic phase depended on the amount of TiO₂, as shown by the change in glass‐transition temperature (T_g) with TiO₂ content. The result of mechanical and thermal tests showed that both the tensile strength and the T_g increased to a maximum value and then decreased with an increasing of TiO₂ because excess particles (e.g., greater than 10 wt % TiO₂) might cause separation or segregation between the organic and inorganic phases. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4272–4280, 2004     

Improving polyethylene–octene elastomer/chitosan by graftation of acrylic acid onto polyethylene–octene elastomer—mechanical properties and biodegradability examination and composites characterization

In this study, the properties of polyethylene–octene elastomer/chitosan (POE/chitosan) and acrylic acid (AA)‐grafted‐polyethylene–octene elastomer/chitosan (POE‐g‐AA/chitosan) were examined using various characterizing instruments. Mechanical and thermal properties of POE deteriorated noticeably when it was blended with chitosan, due to the unsatisfactory compatibility between the two phases. The greater compatibility of POE‐g‐AA with chitosan, due to the formation of ester carbonyl and imide groups, led to a much better dispersion and homogeneity of chitosan in the POE‐g‐AA matrix and consequently to noticeably better mechanical properties. Furthermore, with a lower melting point temperature, the POE‐g‐AA/chitosan blend was more easily processed than POE/chitosan. POE‐g‐AA/chitosan had a higher water resistance than POE/chitosan. Both blends suffered weight loss when buried in soil, especially at high levels of chitosan substitution, indicating that both were biodegradable. The mechanical properties of both blends, such as tensile strength and elongation at break, also deteriorated after being buried in soil. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3882–3891, 2003     

UV‐Irradiation Cured Organic‐inorganic Hybrid Nanocomposite Initiated by Ethoxysilane‐modified Multifunctional Polymeric Photoinitiator through Sol‐gel Process

The UV‐cured organic‐inorganic hybrid nanocomposite (nano‐Si‐m‐PI) was prepared through the photopolymerization of acrylic resin initiated by ethoxysilane‐modified multifunctional oligomeric photoinitiator (Si‐m‐PI). The esterification reaction of 2‐hydroxy‐4′‐(2‐hydroxyethoxy)‐2‐methylpropiophenone (Irgacure 2959) with thioglycolic acid, and the following addition reactions with dipentaerythritol hexaacrylate and then 3‐aminopropyltriethoxysilane were carried out for preparing the Si‐m‐PI. The Si‐m‐PI exhibits the similar UV absorption and molar extinction coefficient with Irgacure 2959. The photoinitiating activity study by photo‐DSC analysis showed that the Si‐m‐PI possesses high photopolymerization rate at the peak maximum (R_p^max) and final unsaturation conversion (P^f) in the cured hybrid films. From the scanning electron microscope (SEM) observation, the SiO₂ nanoparticles dispersed uniformly in the formed nano‐Si‐m‐PI, whereas the aggregation of nanoparticals occurred in nano‐Irg, which was prepared through the photopolymerization of acrylic resin initiated by Irgacure 2959. Moreover, compared with the UV‐cured pure polymer and nano‐Irg, the nano‐Si‐m‐PI showed remarkably enhanced thermal stability and mechanical properties.     

Fabrication and characterization of TiO<Subscript>2</Subscript>–SiO<Subscript>2</Subscript> composite nanoparticles and polyurethane/(TiO<Subscript>2</Subscript>–SiO<Subscript>2</Subscript>) nanocomposite films

TiO₂–SiO₂ composite nanoparticles were prepared by a sol–gel process. To obtain the assembly of TiO₂–SiO₂ composite nanoparticles, different molar ratios of Ti/Si were investigated. Polyurethane (PU)/(TiO₂–SiO₂) hybrid films were synthesized using the “grafting from” technique by incorporation of modified TiO₂–SiO₂ composite nanoparticles building blocks into PU matrix. Firstly, 3-aminopropyltriethysilane was employed to encapsulate TiO₂–SiO₂ composite nanoparticles’ surface. Secondly, the PU shell was tethered to the TiO₂–SiO₂ core surface via surface functionalized reaction. The particle size of TiO₂–SiO₂ composite sol was performed on dynamic light scattering, and the microstructure was characterized by X-ray diffraction and Fourier transform infrared. Thermogravimetric analysis and transmission electron microscopy (TEM) employed to study the hybrid films. The average particle size of the TiO₂–SiO₂ composite particles is about 38 nm when the molar ratio of Ti/Si reaches to1:1. The TEM image indicates that TiO₂–SiO₂ composite nanoparticles are well dispersed in the PU matrix.     

Chemical modification of metallocene‐based polyolefinic elastomers by acrylic acid and its influence on physico‐mechanical properties: Effect of reaction parameters,crystallinity and pendant chain length

In this investigation, solution grafting of acrylic acid (AA) in presence of benzoyl peroxide (BPO) was carried out onto metallocene‐based “poly(ethylene‐octene) elastomers” (POE) as well as “poly(ethylene‐butene) elastomers” (PBE), to impart polarity on the non‐polar rubbery matrix and also to study the effects of crystallinity and pendant chain length on the “grafting percentage” and “percent gel yield” at optimized conditions for all the POE and PBE systems. Reaction parameters were optimized on the basis of the relative proportions of graft and gel formations obtained through %weight gain, Fourier Transform infrared spectroscopy and elemental analysis. The effect of grafting at its maximum level on various physico‐mechanical properties was also thoroughly investigated by using X‐ray diffraction (XRD), differential scanning calorimetry (DSC), mechanical, dynamic mechanical (DMTA), and thermogravimetric analysis (TGA) and the properties were correlated with the structure of the modified polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5529–5540, 2007     

Preparation and electrochemical properties of graphene‐supported Si‐TiO2 nanospheres as anode material for Li‐ion batteries

Graphene‐supported Si‐TiO₂ (Si‐Ti‐GE) composites have been synthesized by a simple polymerization and sintering method. In the Si‐Ti‐GE composites, many small Si‐TiO₂ particles are scattered on the graphene sheet, which can mitigate the agglomeration of the material and further reduce the particle size. The initial discharge capacities of Si‐TiO₂, Si‐Ti‐GE‐1, Si‐Ti‐GE‐2, and Si‐Ti‐GE‐3 are 336.9, 337.2, 339.8, and 356.6 mAh g⁻¹ at the current density of 200 mA g⁻¹, respectively. The discharge rate capacities of TiO₂, Si‐TiO₂, and Si‐Ti‐GE‐3 composites retain 57.5%, 41.7%, and 82.1% at the current density from 100 to 400 mA g⁻¹, respectively. Therefore, the introduction of graphene not only could facilitate the Li⁺ diffusion and electron transport but also could make better electrical conductivity.     

Preparation of Cr‐doped TiO2/SiO2 Photocatalysts and their Photocatalytic Properties

Cr‐doped TiO₂/SiO₂ nanostructured materials were prepared employing a layer‐by‐layer assemblym technique. TiO₂ colloids were synthesized by a sol‐gel method using TiCl₄ as a precursor. The experimental results showed that sphere‐type TiO₂ particles on SiO₂ exhibited uniform shape and a narrow size distribution. The amount of Ti (wt %) increased as a function of the number of the coating layers. The coatingv layers was composed of anatase titania nanocrystals at 550 °C. The onset of band‐gap transition for Crdoped TiO₂/SiO₂ showed a red shift compared with that for the undoped TiO₂/SiO₂. And the photocatalytic activity of Cr‐doped TiO₂/SiO₂ was higher than that of undoped sample.     

Dispersion of TiO2 on high‐surface‐area mesoporous silica: functionalization with tungstophosphoric acid and application in solvent‐free,aerobic oxidation of n‐hexadecane

Imidazole type ionic liquid, 1‐hexadecyl‐3‐methylimidazolium chloride, was used to template the synthesis of high‐surface‐area mesoporous silica under acidic conditions and crystalline titanium dioxide (TiO₂) nanoparticles of anatase phase were inserted utilizing a solvent evaporation‐induced method. The surface area of more than 700 m² g^?1 was obtained after TiO₂ impregnation. Further, the polyoxometalate, 12‐tungstophosphoric acid (PW₁₂) was dispersed on the surface of TiO₂ to form PW₁₂–TiO₂–silica hybrid catalytic materials. The catalytic activity of this hybrid material was tested for solvent‐free, aerobic oxidation of n‐hexadecane. The experimental investigation shows that PW₁₂–TiO₂ nanocrystals did not block the pore channels and gave good conversion. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis and Structural Analysis of Au-Doped TiO2/SiO2 Mixed Oxide Films Prepared by Sol-Gel Process

The systematic modifications of silica matrix as a function of modified Ti-alkoxide contents (Au nanocrystals doped TiO₂/SiO₂ mixed oxide thin films) have been investigated by the sol-gel process. A structural analysis on the various steps of the hydrolysis-condensation process as well as solid powder is determined by IR, UV-Visible, and ²⁹Si NMR spectroscopy. ²⁹Si MAS spectra are characterized by broad lines for the three types of sites. Different distributions (Q ², Q ³, and Q ⁴ units) observed in the TiO₂/SiO₂ (1 : 3) sample. Proper control of the process condition, modifying the Ti alkoxide as a less reactive precursor, improves the increase the amount of Ti–O–Si bonding in the silica network of TiO₂/SiO₂ mixed oxide matrices and the distribution of metal oxides. This method can be used for the preparation of homogeneous metal and metal-metal alloy nanocrystals deposition from mixed oxide thin films.     

Non‐surfactant template‐directed synthesis of SiO2‐polyimide hybrid self‐standing films with ordered mesoporous structure

The silica‐PI hybrid self‐standing films with ordered mesoporous structure have been prepared by using dibenzoyl‐L ‐tartaric acid (L ‐DBTA) as non‐surfactant template under mild sol–gel route. Polyimide matrix was obtained from polyamic acid (PAA) via thermal imidization process and the template was removed in this process. The PI‐based hybrid film with 20 wt% SiO₂ obtained from DBTA presented the ordered mesoporous channels with average pore size of about 2.0 nm and BET surface area of 1167 m²/g. FTIR and SEM studies indicated that the hydrogen bond interaction between the carboxylic groups of DBTA and benzamide bonds of PAA made the PAA possibly participate in the assembly process of the aggregates of the non‐surfactant template molecules. The mechanical, thermal and some physical properties of these hybrid films materials were also characterized. Copyright © 2010 John Wiley & Sons, Ltd.     

Electrochemically reduced tungsten‐based active species as catalysts for cross‐metathesis reactions: cross‐metathesis of erucic acid with 2‐octene

The cross‐metathesis of erucic acid, (CH₃(CH₂)₇CH?CH(CH₂)₁₁COOH), with an excess of 2‐octene in the presence of an electrochemically produced tungsten‐based catalyst has been studied. Cross‐ and self‐hydrocarbon products, viz. 2‐undecene (C₁₁), 6‐dodecene (C₁₂) and 6‐pentadecene (C₁₅), were detected. The influence of several parameters, such as the 2‐octene/erucic acid and 2‐octene/catalyst ratios and the reaction time, on the yield of the cross‐metathesis product, 6‐pentadecene, was studied. The cross‐metathesis of functionalized olefins in the presence of an Al–e^?–WCl₆–CH₂Cl₂ system has not been reported in the literature so far. The cross‐metathesis products in the presence of this catalyst system can be obtained with high yield and high specificity. Copyright © 2004 John Wiley & Sons, Ltd.     

Polymerization of neat 2‐ethylhexyl acrylate induced by a pulsed electron beam

The bulk polymerization of 2‐ethylhexyl acrylate (2‐EHA), induced by a pulsed electron beam, was investigated with pulse radiolysis, gravimetry, and Fourier transform infrared spectroscopy. The roles of the dose rate, pulse frequency, and added acrylic acid (AA) in the polymerization of 2‐EHA were examined at ambient temperature. In the range of 12.6–71.2 Gy/pulse, the polymerization of 2‐EHA was dose‐rate‐dependent: at the same total dose, a lower dose rate yielded a higher conversion. Also, a lower pulse rate gave a higher conversion at the same total dose. The addition of up to 10 wt % AA showed no increase in the conversion of 2‐EHA at a low conversion (8 kGy), but at a higher conversion (16 kGy), a 20 wt % increase in the conversion of 2‐EHA was observed. The estimated values (1.6 ± 0.3) × 10^?3 (dm³ s)^3/2 mol^?1 s^?1/2 for k_p(G/2k_t)^1/2 and 2.6 ± 0.8 dm³ s J^?1 for 2k_tG (where k_p is the rate constant of propagation, k_t is the rate constant of bimolecular termination, and G is the yield of free radicals) were obtained at relatively low conversions. The reaction rate constant of the addition of 2‐EHA^· free radicals to the monomer was measured by pulse radiolysis and found to be 2.8 × 10² mol^?1 dm³ s^?1. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 196–203, 2003     

Sulfonation of metallocene‐based polyolefinic elastomers and its influence on physicomechanical properties: Effect of reaction parameters,styrene grafting,and pendant chain length

Direct sulfonation and styrene‐mediated sulfonation were carried out onto metallocene‐based poly(ethylene‐co‐octene) (POE) and poly(ethylene‐co‐butene) (PBE) elastomers to impart polarity on the completely nonpolar rubbery matrices and to prepare a new class of elastomer. The influence of styrene‐grafting and pendant chain length on the degree of sulfonation was also studied. The effects of sulfonation, styrene grafting and styrene‐mediated sulfonation at their optimized levels on various physicomechanical properties were thoroughly investigated, and the resultant properties were correlated with structures of the modified elastomers. Higher extent of sulfonic acid groups were introduced through direct sulfonation in comparison with the styrene‐mediated sulfonation, whereas better thermal and mechanical properties were obtained through styrene‐mediated sulfonation in comparison with the direct sulfonation process. PBE had shown higher degree of sulfonation and percentage grafting than POE. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 8023–8040, 2008     

Correlation of morphological parameters and mechanical performance of polyamide‐612/poly (ethylene–octene) elastomer blends

Blends of polyamide‐612 (PA‐612) and maleic anhydride grafted poly (ethylene–octene) elastomer (POE‐g‐MA) as an impact modifier have been prepared in the composition range of 0–35 wt. % of POE‐g‐MA and subsequently investigated for their structural, thermal, mechanical, dynamic mechanical properties and morphological attributes. X‐ray diffraction studies revealed a decrease in crystallinity whereas the thermal properties such as onset to degradation temperature and crystallization temperature remained broadly unaffected. Nearly three‐fold increase in the impact strength is registered accompanied by substantial increase in tensile failure strain, though tensile modulus (E) and tensile yield strength (σ _y) decreased with increase in impact modifier content. Dynamic mechanical analysis exhibited a singularity response in the loss factor in the temperature range of ~10°C–50°C. Micromechanical aspects were analyzed using conventional theoretical models for low strain mechanical response (E) such as rule of mixtures and foam model and for high strain mechanical response (σ _y) such as Nikolais–Narkis model and porosity model. Impact toughness and strain‐at‐break of the investigated composition were successfully correlated to the domain size (D_n) of the dispersed phase and their inter‐particle distances (τ). Scanning electron microscopy showed the coalescence of domains of the dispersed phase at higher POE content and thus reiterates the crucial role of inter‐particle distance in controlling the toughening mechanism of POE blended PA‐612. Copyright © 2013 John Wiley & Sons, Ltd.     

Photocurrent Enhancement of Dye‐Sensitized Solar Cells owing to Increased Dye‐Adsorption onto Silicon‐Nanoparticle‐Coated Titanium‐Dioxide Films

The inverse‐micellar preparation of Si nanoparticles (Nps) was improved by utilizing sodium naphthalide. The Si Nps were subsequently functionalized with 4‐vinylbenzoic acid for their attachment onto TiO₂ films of dye‐sensitized solar cells (DSSCs). The average diameter of the COOH‐functionalized Si (Si? COOH) Nps was 4.6(±1.7) nm. Depth profiling by secondary‐ion mass spectrometry revealed that the Si Nps were uniformly attached onto the TiO₂ films. The number of Ru^II dye molecules adsorbed onto a TiO₂ film that was treated with the Si? COOH Nps was 42 % higher than that on the untreated TiO₂ film. As a result, DSSCs that incorporated the Si? COOH Nps exhibited higher short‐circuit photocurrent density and an overall energy‐conversion efficiency than the untreated DSSCs by 22 % and 27 %, respectively. This enhanced performance, mostly owing to the intramolecular charge‐transfer to TiO₂ from the dye molecules that were anchored to the Si? COOH Nps, was confirmed by comparing the performance with two different Ru^II–bipyridine dyes (N719 and N749).     

Compositing Amorphous TiO2 with N‐Doped Carbon as High‐Rate Anode Materials for Lithium‐Ion Batteries

Compositing amorphous TiO₂ with nitrogen‐doped carbon through Ti? N bonding to form an amorphous TiO₂/N‐doped carbon hybrid (denoted a‐TiO₂/C? N) has been achieved by a two‐step hydrothermal–calcining method with hydrazine hydrate as an inhibitor and nitrogen source. The resultant a‐TiO₂/C? N hybrid has a surface area as high as 108 m² g^?1 and, when used as an anode material, exhibits a capacity as high as 290.0 mA h g^?1 at a current rate of 1 C and a reversible capacity over 156 mA h g^?1 at a current rate of 10 C after 100 cycles; these results are better than those found in most reports on crystalline TiO₂. This superior electrochemical performance could be ascribed to a combined effect of several factors, including the amorphous nature, porous structure, high surface area, and N‐doped carbon.     

Visible Light Photocatalytic Activity of Pt/N‐TiO2 towards Enhanced H2 Production from Water Splitting

Present work mainly focuses on experimental investigation to improvement of hydrogen production by water photoelectrolysis. An experimental facility was designed and constructed for visible light photocatalysis. A series of N‐TiO₂ photocatalysts impregnated with platinum on the surface of N‐TiO₂ were prepared. Hydrogen production upon irradiating aqueous Pt/N‐TiO₂ suspension with visible light was investigated. The shift in excitation wavelength of TiO₂ was 380 nm improved the yield of hydrogen production by N‐TiO₂ and Pt/N‐TiO₂. We used a 400 W mercury arc lamp combined with a 400 nm cutoff filter eliminating all the wavelengths under 400 nm. Pt/N‐TiO₂ material was characterized with TPR, reflective UV/Visible spectroscopy and TEM. The best hydrogen production rate obtained for this setup for N/Ti = 10, 0.05 wt% Pt/N‐TiO₂, through water splitting was about 772 μmolh^?1g^?1.     

Application of 1-(2-Pyridylazo)-2-naphthol Anchored SiO2 Nanoparticles for the Preconcentration of Trace Pb2+ from Different Water and Food Samples

SiO₂‐PAN nanoparticles has been synthesized by reacting silica nanoparticles with 3‐aminopropyltriethoxysilane, formaldehyde and 1‐(2‐pyridylazo)‐2‐naphthol and characterized by FT‐IR and SEM which were used as new sorbent for the preconcentration of trace amount of Pb²⁺ from various samples. Conditions of the analysis such as preconcentration factor, effect of pH, sample volume, shaking time, elution conditions and effects of interfering ions for the recovery of analyte were investigated. The adsorption capacity of the nanometer SiO₂‐PAN was found to be 168.34 μmol/g at optimum pH and the detection limit (3δ) was 0.63 µg/L. The extractant showed rapid kinetic sorption. The adsorption equilibrium of Pb²⁺ on the nanometer SiO₂‐PAN was achieved within 15 min. Adsorbed Pb²⁺ was easily eluted with 6 mL of 4 mol·L^?1 hydrochloric acid. The maximum preconcentration factor was 50. The method was applied to determine trace amounts of Pb²⁺ in different samples (water and food samples).     

Synthesis,characterization, and optimum reaction conditions of oligo‐2‐[(pyridine‐2‐yl‐methylene) amino] phenol

The reaction conditions of the oxidative polycondensation of 2‐[(pyridine‐2‐yl‐methylene) amino] phenol (2‐PMAP) with air O₂, H₂O₂, and NaOCl were studied in an aqueous alkaline medium between 60 and 90 °C. Oligo‐2‐[(pyridine‐2‐yl‐methylene) amino] phenol (O‐2‐PMAP) was characterized with ¹H NMR, Fourier transform infrared, ultraviolet–visible, size exclusion chromatography (SEC), and elemental analysis techniques. Moreover, solubility testing of the oligomer was performed in polar and nonpolar organic solvents. With the NaOCl, H₂O₂, and air O₂ oxidants, the conversions of 2‐PMAP into O‐2‐PMAP were 98, 87, and 62%, respectively, in an aqueous alkaline medium. According to SEC, the number‐average molecular weight, weight‐average molecular weight, and polydispersity index of O‐2‐PMAP were 2262 g mol^?1, 2809 g mol^?1, and 1.24 with NaOCl, 3045 g mol^?1, 3861 g mol^?1, and 1.27 with air O₂, and 1427 g mol^?1, 1648 g mol^?1, and 1.16 with air H₂O₂, respectively. Also, thermogravimetric analysis showed that O‐2‐PMAP was stable against thermooxidative decomposition. The weight loss of O‐2‐PMAP was 96.68% at 900 °C. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2717–2724, 2004