Silicon‐based mercaptans: High‐performance monomers for thiol‐ene photopolymerization

Ester‐free silane and siloxane‐based thiol monomers were successfully synthesized and evaluated for application in thiol‐ene resins. Polymerization reaction rates, conversion, network properties as well as degradation experiments of those thiol monomers in combination with triallyl‐1,3,5‐triazine‐2,4,6(1H,3H,5H)‐trione (TATT) as ene component were performed and compared with formulations containing the commercially available mercaptopropionic ester‐based thiol pentaerythritol tetra‐3‐mercaptopropionate. Kinetic analysis revealed appropriate reaction rates and conversions reaching 90% and higher. Importantly, storage stability tests of those formulations clearly indicate the superiority of the synthesized mercaptans compared with pentaerythritol tetra‐3‐mercaptopropionate/TATT resins. Moreover, photocured samples containing silane‐based mercaptans provide higher glass transition temperatures and withstand water storage without a significant loss in their network properties. This behavior together with the observed excellent degradation resistance of photocured silane‐based thiol/TATT formulations make these multifunctional mercaptans interesting candidates for high‐performance applications, such as dental restoratives and automotive resins. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 418–424     

Analysis the microscopic solid‐based wear process in the chemical mechanical planarization

Chemical mechanical planarization (CMP), being the important technique of realizing the surface planarization, has already been widely applied in the microelectronic and computer industry. The abrasive size employed in the CMP, far less than that employed in the conventional grinding and material removal during CMP, is on the order of atoms or clusters of atoms and molecules. Classical continuum mechanics cannot give a reasonable explanation about the phenomenon in the CMP. Large‐scale classical molecular dynamics simulation of tribology interaction among nanoparticles and materials surface has been carried out to investigate the physical essence of surface planarization. The results show that simultaneous impact of several abrasive particles or the repeated impact of abrasive particles leads to material failure. For individual asperity contact in the CMP, non‐obvious Archard adhesive wear or abrasive wear is observed. The contact area is not entirely dependent upon the external pressure but also closely related to the relative position because of lateral motion between the particles and the substrate. The results also justify that no single wear mechanism dominates all operating conditions; different wear mechanisms operate with their relative importance changing as the sliding conditions change. As the slurry particles slide relative to the wafer surface, the atomic groups experience three stages, namely, interlock, elastic–plastic deformation and finally slip process; the surface planarization is mainly accomplished in the last two stages. Copyright © 2011 John Wiley & Sons, Ltd.     

Experimental method for wear assessment of sealing elastomers

Elastomeric dynamic seals are components to prevent or to limit lubricant leakage in machinery. Nevertheless, they wear away under certain working conditions. Mostly, wear exists by starvation of lubricant film (two-body abrasion) and interaction with hard debris (three-body abrasion). This work aims to propose a suitable test methodology toward determining two-body and three-body abrasive wear rates of elastomers by using a TE66 Micro-Scale Abrasion Tester. In the tests, sections of silicone rubber were used. The experiments were divided in two parts. Firstly, dry runs were carried out replicating the two–body abrasion mechanism. Secondly, trials were run using two different media (contaminated oil and slurry) to reproduce three-body abrasive wear. Large viscoelastic deformations were generated in the samples and then they were considered for the wear estimation. In conclusion, the method shows advantages which make it suitable as an alternative test to obtain the wear behavior of sealing elastomers.     

Comparative study of the effects of nano‐sized and micro‐sized CF and PTFE on the thermal and tribological properties of PEEK composites

The tribological characteristics of PEEK composites fretting against GCr 15 steel were investigated by a SRV‐IV oscillating reciprocating ball‐on‐disk tribometer. In order to clarify the effect of type and size of fillers on the properties of PEEK composites, nano‐sized and micro‐sized CF and PTFE fillers were added to the PEEK matrix. The thermal conductivity, hardness, and fretting wear properties of PEEK composites reinforced by CF or PTFE were comparatively studied. The results showed that the type and size of the fillers have an important effect on both the friction coefficient and wear rate, by affecting their thermal conductivity, hardness, as well as the surface areas of their transfer films. In comparison, the effect on improving the tribological properties of micro‐sized CF was superior to that of nano‐sized CF, while the effect of nano‐sized PTFE was superior to that of micro‐sized PTFE. Considering the acceptable friction coefficient and wear rate of the composite under the fretting wear test, it seemed that 4% nCF, 20% mCF, 2% nPTFE and 10% mPTFE were desired additive proportions. And it also can be found that during the fretting wear test, the abrasive and adhesive wear resulted in accumulative debris at the contacting surface. The transfer films made of debris were formed on the counterfaces.     

Study on mono-dispersed nano-size silica by surface modification for underfill applications

In order to improve the rheological behavior of the nanosilica composite no-flow underfill, filler surface treatment using silane coupling agents was investigated to reduce the filler-filler interaction and to achieve the mono-dispersity of the nanosilica in the underfill resin. The experimental conditions of the surface treatment were investigated in a design of experiment (DOE) in terms of the pre-treatment methods, coupling agent types, concentrations, and treatment durations. The particle dispersion after treatment was evaluated by the laser particle analyzer and the transmission electron microscopy (TEM). A mono-dispersed nanosilica solution in the polar medium was achieved using optimal experimental condition. The surface chemistry of the nanosilica was studied using Fourier transformed infrared spectroscopy (FTIR). The wettability of underfill resin and water on the silane treated glass slides was studied using a goniometer. Based on the investigations, the silane-treated nanosilica fillers were incorporated into an underfill resin to formulate a nanocomposite no-flow underfill. It was found that the proper filler treatment could significantly reduce the viscosity of the nanocomposite.     

Comparative study of microstructure and tribological behavior of TiC/a‐C:H and a‐C:H coatings in a sand‐dust environment

TiC/a‐C:H and a‐C:H nanocomposite coatings were prepared on AISI 440C steel substrates using magnetron sputtering process. A comparative study was made on their composition and microstructure by Raman spectroscopy and high‐resolution transmission electron microscopy (HRTEM). The tribological properties of two types of carbon‐based coatings were investigated by pin‐on‐disc tribometer under the sand‐dust conditions concerning the influence of applied load, amount of sand and sand particle sizes. The results show that these carbon‐based coatings exhibited high tribological performance with low friction coefficient and wear rate under the sand‐dust environments. However, the TiC/a‐C:H coatings exhibit relatively higher fluctuant friction coefficient as well as higher wear rate in comparison with the a‐C:H coatings under sand‐dust environments. The formation of nanocrystalline hard TiC phase distributed in amorphous carbon matrix decreased the residual stress but significantly increased the hardness and Young's modulus of TiC/a‐C:H coatings, and consequently caused a relatively higher abrasive and fatigue wear loss under the sand‐dust conditions. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis of polyether‐based polyurethane‐silica nanocomposites with high elongation property

The NCO‐terminated prepolymers, prepared by reacting a mixture of poly(tetramethylene glycol) and fumed nanosilica with 4,4′‐diphenylmethane diisocyanate, were chain‐extended with 1,4‐ butanediol to yield polyurethane‐silica nanocomposites. The nanosilica particles were well dispersed in the polyurethane matrix up to 3 wt%. The polyurethane chains in the interfaces were covalently linked to the nanosilica surfaces through urethane bonds. Introduction of the nanosilica into the polyurethane enhanced both tensile strength and elongation of the resulting nanocomposite films. Especially, the elongation at break of the nanocomposite films containing 1 wt% nanosilica was 3.5 times greater than that of the pure polyurethane films. Copyright © 2005 John Wiley & Sons, Ltd.     

Graphite Micropowder Modified with 4‐Amino‐2,6‐diphenylphenol Supported on Basal Plane Pyrolytic Graphite Electrodes: Micro Sensing Platforms for the Indirect Electrochemical Detection of Δ9‐Tetrahydrocannabinol in Saliva

Graphite micropowder has been modified with 4‐amino‐2,6‐diphenylphenol immobilized onto a basal plane pyrolytic graphite electrode and explored for the indirect electrochemical sensing of Δ⁹‐tetrahydrocannabinol in artificial saliva. The protocol is based on the electrochemical formation of quinoneimine which specifically reacts with Δ⁹‐tetrahydrocannabinol resulting in the loss of the quinoneimine which can be monitored via voltammetry. It is demonstrated that Δ⁹‐tetrahydrocannabinol can be detected in artificial saliva over the micromolar range. Such a protocol may find application in screening for drug abuse.     

Determination of strobilurin fungicides in cotton seed by combination of acetonitrile extraction and dispersive liquid−liquid microextraction coupled with gas chromatography

The simultaneous determination of four strobilurin fungicides (picoxystrobin, kresoxim‐methyl, trifloxystrobin, and azoxystrobin) in cotton seed by combining acetonitrile extraction and dispersive liquid?liquid microextraction was developed prior to GC with electron capture detection. Several factors, including the type and volume of the extraction and dispersive solvents, extraction condition and time, and salt addition, were optimized. The analytes were extracted with acetonitrile from cotton seed and the clean‐up was carried out by primary secondary amine. Afterwards, 60 μL of n‐hexane/toluene (1:1, v/v) with a lower density than water was mixed with 1 mL of the acetonitrile extract, then the mixture was injected into 7 mL of distilled water. A 0.1 mL pipette was used to collect a few microliters of n‐hexane/toluene from the top of the aqueous solution. The enrichment factors of the analytes ranged from 36 to 67. The LODs were in the range of 0.1 × 10^?3?2 × 10^?3 mg/kg. The relative recoveries varied from 87.7 to 95.2% with RSDs of 4.1?8.5% for the four fungicides. The good performance of the method, compared with the conventional pretreatments, has demonstrated it is suitable for determining low concentrations of strobilurin fungicide residues in cotton seed.     

UV‐cured polyester‐acrylate nanocomposite films with silane‐grafted silica nanoparticles

UV‐curing technique was employed in this study to prepare polyester‐acrylate nanocomposite films with silane‐grafted silica nanoparticles. Methacryloxypropyl trimethoxysilane was grafted to the surfaces of silica nanoparticles to improve dispersion of silica nanoparticles as well as interfacial adhesion between the resin matrix and silica nanoparticles. The silane‐grafting was confirmed by nuclear magnetic resonance and infrared spectroscopy. The effects of the silane‐grafting on the mechanical and optical properties as well as UV‐curing behavior of the nanocomposite films were investigated. The tensile strength, transmittance, UV‐curing rate, and final chemical conversion of the nanocomposite films were increased by use of the grafted silica nanoparticles as compared to the use of neat silica nanoparticles. Copyright © 2011 John Wiley & Sons, Ltd.     

Effects of UV irradiation on tribological properties of nano‐TiO2 thin films

One‐layer and two‐layer nano‐TiO₂ thin films were prepared on the surface of common glass by sol–gel processing. Water contact angle, surface morphology, tribological properties of the films before and after ultraviolet (UV) irradiation were investigated using DSA100 drop shape analyzer, scanning probe microscopy (SPM), SEM and universal micro‐materials tester (second generation) (UMT‐2MT) friction and wear tester, respectively. The stored films markedly resumed their hydrophilicity after UV irradiation. But UV irradiation worsened tribological properties of the films. After the film was irradiated by UV, the friction coefficient between the film and GCr15 steel ball increased about 10–50% and its wear life shortened about 20–90%. Abrasive wear, brittle break and adherence wear are the failure mechanisms of nano‐TiO₂ thin films. It was believed that UV irradiation increased surface energy of the film and then aggravated adherence wear of the film at initial stage of friction process leading to severe brittle fracture and abrasive wear. Copyright © 2009 John Wiley & Sons, Ltd.     

Facile preparation of superhydrophobic and oleophobic surfaces via the combination of Cu(0)‐mediated reversible‐deactivation radical polymerization and click chemistry

The fabrication of novel hydrophobic, superhydrophobic, and oleophobic surfaces on glass using nanosilica particles modified with polymer brushes prepared via surface initiated Cu(0)‐mediated reversible‐deactivation radical polymerization was demonstrated. Monomers including n‐butyl acrylate, 2,2,2‐trifluoroethyl methacrylate, and 1,1,1,3,3,3‐hexafluoroisopropyl acrylate were used to synthesize a series of nanosilica–polymer organic/inorganic hybrid materials. Products were analyzed using infrared spectroscopy, thermogravimetric analysis, scanning and transmission electron microscopy. The coated nanosilica showed core–shell structures that contains polymer brushes up to 67 wt %. The application of these particles for modifying surface wettability was examined by covalently attaching them to glass via a recently developed one‐pot “grafting to” methodology using “thio‐bromo click” chemistry. Atomic force microscopy topographic images show up to 25 times increase in roughness of the coated glass compared to blank glass sample. Contact angle measurements showed that nanosilica coated with PBA and PTFEM produced hydrophobic glass surfaces, while a superhydrophobic and oleophobic surface was generated using nanosilica functionalized with PHFIPA. This novel methodology can produce superhydrophobic and oleophobic surfaces in an easy and fast way without the need for tedious and time‐consuming processes, such as layer‐by‐layer deposition, high temperature calcination, and fluorinated oil infusion. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018     

Free‐radical‐promoted cationic photopolymerization under visible light in aerated media: New and highly efficient silane‐containing initiating systems

New systems for the visible‐light‐induced polymerization of cationic resins working through a free‐radical‐promoted process are presented. They are based on a photoinitiator (camphorquinone, isopropylthioxanthone, Eosin), a silane, and a diphenyl iodonium salt, the new compound being the silane. The overall efficiency is strongly affected by the silane structure. The rates of polymerization and final percent conversion are noticeably higher than those obtained in the presence of already studied reference systems. Moreover, contrary to previously investigated free‐radical‐promoted cationic polymerizations, oxygen does not inhibit the process and an unusual enhancement of the polymerization kinetics is found in aerated conditions: such an observation seems to have never been reported so far. The excited state processes and the role of oxygen as revealed by laser flash photolysis are discussed. The particular behavior of the silyl radicals is outlined. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2008–2014, 2008     

Biohydrogen Production from Mushroom Cultivation Waste by Anaerobic Solid‐state Fermentation

Mushroom cultivation waste (MCW) is a polypropylene bag stuffed with wood flour and nutrients for growing mushroom, which is a feasible feedstock for anaerobic biohydrogen production owing to its abundant availability, high organic and nutrient content. This study optimized the seed inoculum from various waste sludges (sewage sludge, cow dung and pig slurry), nutrient addition and operation conditions (moisture content and MCW powder particle size) for maximal biohydrogen production by solid‐state fermentation (SSF). SSF batch test was operated at a MCW 3 g total volatile solid (TVS)/L, temperature 55 °C and rotation speed of 15 rpm with a vertical rotative shaker. The peak hydrogen production performance of hydrogen production rate (HPR) 9.50 mol H₂/kg‐d and hydrogen yield (HY) 0.29 mmol H₂/g TVS) are obtained using sewage sludge 2 seed inoculum, nutrients addition, moisture content 70 % and particle size of 1.190～0.590 mm. The results show that the MCW has the potential for hydrogen production by anaerobic mixed microflora using solid‐state fermentation. The bioenergy of 1842 kWh while using SSF to conver MCW to produce biohydrogen and it could reduce CO₂ emission of 114–178 kg per year comparing using fossil fuel such as coal, fuel oil and natural gas.     

Formation of an in situ nanosilica nanomatrix via graft copolymerization of vinyltriethoxysilane onto natural rubber

Natural rubber (NR) with an in situ nanosilica nanomatrix was characterized in present work. The in situ nanosilica nanomatrix was prepared via graft copolymerization of a silane monomer, vinyltriethoxysilane (VTES), onto deproteinized NR (DPNR) in latex stage using tetrapentamine (TEPA)/tert‐butylhydroperoxide (TBHPO) as initiators. VTES conversion of more than 80% was obtained, and it depended on VTES concentration. The graft copolymer structure was characterized by Fourier transform infrared (FT‐IR), solution‐state proton nuclear magnetic resonance (¹H‐NMR), and solid‐state ²⁹Si‐NMR spectroscopy. FT‐IR analysis of the graft copolymer confirmed the formation of in situ silica particles, while solution‐state ¹H‐NMR and solid‐state ²⁹Si‐NMR revealed the partial hydrolysis of the ethoxy groups and polycondensation of the silanol groups. The formation of nanosilica particles enhanced thermal and mechanical properties of the graft copolymer. Morphology observations of the in situ nanosilica nanomatrix through scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that the spherical nanosilica particles form a nanomatrix surrounding NR particle. The formation of the nanomatrix was proved to enhance mechanical properties for NR materials.     

A Microwave‐assisted Headspace Solid‐phase Microextraction for Rapid Determination of Synthetic Polycyclic and Nitro‐aromatic Musks in Fish Samples

Rapid solvent‐free microwave‐assisted headspace solid‐phase microextraction (MA‐HS‐SPME) coupled with gas chromatography‐mass spectrometry (GC‐MS) was developed to determine synthetic polycyclic and nitro‐aromatic musks in fish samples. Four commonly used synthetic musks, galaxolide (HHCB), tonalide (AHTN), musk xylene (MX) and musk ketone (MK) were employed in the method development and validation. The parameters (microwave irradiation time, irradiation power, amount of water addition, pH value and addition of NaCl) affecting the extraction efficiency of analytes from fish slurry were systematically investigated and optimized. The best extraction conditions were achieved when the fish sample 2‐g mixed with 4‐mL methanol and 15‐mL deionized water (containing 4 g of NaCl, pH 2.0 in a 40‐mL sample‐vial) was microwave irradiated at 80 watt for 5 min. The limits of quantification (LOQ) were 0.4 to 1.2 ng/g in 2‐g of wet tissue. The precision for these analytes, as indicated by relative standard deviations, were less than 9% for both intra‐ and inter‐day analysis. Accuracy, expressed as the mean extraction recovery, was between 80 to 92%. A standard addition method was used to quantitate these four synthetic musks, and the total concentrations ranged from 2.1 to 23.1 ng/g in various fish samples.     

Evaluation of solid‐phase extraction procedures for the quantitation of venlafaxine in human saliva by high‐performance liquid chromatography

In recent years, the use of human saliva for diagnostic purposes has evoked great interest. Thus, the aim of this study was to choose the optimal solid‐phase extraction cartridges and extraction solvents for the quantitation of venlafaxine in saliva. Blank saliva samples spiked with venlafaxine concentrations between 25 and 750 ng/mL were analyzed using five solid‐phase extraction columns (C18, C8, Strata‐X, Strata‐X‐C, and Strata‐X‐AW), washing solvents (deionized water, phosphate buffer at pH 5.5, and their mixtures with methanol), and elution solvents (methanol, acetonitrile, and their mixtures with 25% ammonia). A high‐performance liquid chromatography system was used to quantify venlafaxine in saliva. The results of this study revealed that nine of 25 procedures enabled quantitation of venlafaxine in the tested concentration range. The procedure that used a C18 cartridge, a mixture of methanol and deionized water as the washing solvent, and methanol as the elution solvent was the most effective and allowed quantitation of all venlafaxine concentrations with an acceptable recovery. In contrast, the Strata‐X‐C cartridge could not detect venlafaxine at the lowest concentration (25 ng/mL). The data acquired from the high‐performance liquid chromatography system were confirmed by a multivariate data analysis.     

Surface and interface characterization of polyester‐based polyurethane/nano‐silica composites

Polyester‐based polyurethane/nanosilica composites were prepared via in situ polymerization and investigated by contact angle measurement, transmission electron microscopy (TEM), atomic force microscopy (AFM) and peel testing in an Instron testing machine. The contact angle and surface free energy results show that nanosilica tended to enrich at the interface between nanocomposite polymers and the substrates, TEM indicated that nanosilica particles were evenly dispersed in the bulk and AFM demonstrated that nanoparticles were located at both the surfaces and interfaces of nanocomposite polymers and that the roughness of both the surfaces and interfaces had a decreasing tendency as the nanosilica content increased, as did the adhesion strength between the nanocomposite polymers and substrates. Copyright © 2003 John Wiley & Sons, Ltd.     

Molecular mobility of free‐radical‐functionalized carbon‐nanotube/siloxane/poly(urea urethane) nanocomposites

Multiwalled carbon nanotubes (MWNTs) were functionalized by a free‐radical reaction of vinyltriethoxysilane and were blended with poly(urea urethane) (PUU) containing poly(dimethylsiloxane) as a soft segment. PUU was end‐capped with aminopropyltriethoxysilane (A‐silane) or phenyltriethoxysilane (P‐silane).A‐silane‐end‐capped PUU was covalently bonded to functionalized MWNTs, whereas P‐silane‐end‐capped PUU was noncovalently bonded to pristine MWNTs by a π–π interaction. Fourier transform infrared, Raman spectra, and thermogravimetric analysis confirmed the functionalization of MWNTs. The results showed that the optimal reaction time of the functionalization of MWNT was 8 h, and the organic content of the modified carbon nanotubes reached 35.22%. Solid‐state nuclear magnetic resonance and dynamic mechanical analysis were used to investigate the molecular structure and molecular mobility of the carbon‐nanotube/PUU nanocomposites. A‐silane PUU covalently bonded to MWNTs showed a considerable reduction in the molecular motion of the soft segment, which led to the glass‐transition temperature decreasing from ?117 to ?127 °C as MWNTs were incorporated. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6084–6094, 2005     

Investigating retention characteristics of a mixed‐mode stationary phase and the enhancement of monolith selectivity for high‐performance liquid chromatography

The synthesis and chromatographic behavior of an analytical size mixed‐mode bonded silica monolith was investigated. The monolith was functionalized by an in situ modification process of a bare silica rod with chloro(3‐cyanopropyl)dimethyl silane and chlorodimethyl propyl phenyl silane solutions. These ligands were selected in order to combine both resonance and nonresonance π‐type bonding within a single separation environment. Selectivity studies were undertaken using n‐alkyl benzenes and polycyclic aromatic hydrocarbons in aqueous methanol and acetonitrile mobile phases to assess the methylene and aromatic selectivities of the column. The results fit with the linear solvent strength theory suggesting excellent selectivity of the column was achieved. Comparison studies were performed on monolithic columns that were functionalized separately with cyano and phenyl ligands, suggesting highly conjugated molecules were able to successfully exploit both of the π‐type selectivities afforded by the two different ligands on the mixed‐mode column.