Induction heating for surface triggering styrene polymerization on titanium modified with ATRP initiator

Titanium and its alloys present high interests for technological applications due to their high corrosion resistance, mechanical properties and biocompatibility. In combination with these remarkable characteristics, some Ti applications require specific surface properties that can be imparted with suitable surface functionalizations of the TiO(2) oxide layer. The present work aims to study the surface-initiated ATR polymerization of styrene on titanium substrates, using grafted 11-(2-bromoisobutyrate)-undecyl-1-phosphonic acid as initiator and to compare the impact of two different heating ways on the efficiency of this polymerization: induction vs. conventional heating. The ability of the initiator to bind titanium substrates and act as an initiator for ATRP of styrene is investigated: both heating conditions led to the polymerization of styrene on modified titanium substrates. However, induction heating appeared to be much more efficient than conventional heating, leading to the formation of a thicker, much denser polystyrene layer than conventional heating after only 1h of polymerization.     

Ruthenium(II)-catalysed cycloisomerisation of 1,6-dienes by focused microwave dielectric heating: improved rates and selectivities leading to exo-methylenecyclopentanes

We herein report the effect of microwave dielectric heating in the Ru-catalysed cycloisomerisation of 1,6-dienes. Substantially improved reaction rates are attained for a series of 1,6-diene substrates, with equivalent or higher isomeric purity than conventional thermal heating.     

Effect of microwave heating on Ullmann-type heterocycle-aryl ether synthesis using chloro-heterocycles

Ullmann ether synthesis was conducted on a variety of chloro-heterocycles with different phenols using optimized conditions involving copper powder and cesium carbonate. On many substrates, microwave heating afforded higher yields in significantly shorter reaction times compared to conventional heating conditions. These findings provide a facile method for aryl ether synthesis from chloropyridines, chloroquinolines, and chlorobenzothiazoles.     

Microwave processing of TiO2 blocking layers for dye-sensitized solar cells

The microwave heat treatment of blocking layers for dye-sensitized solar cells has been investigated. It has been found that the solar cell efficiencies achieved with microwave heating were considerably higher than those achieved with conventional heating at low temperatures (100°C). This was attributed to microwave heating providing better sintering of the blocking layer and better interfacial contact between the substrate and the TiO₂ layers. These results are promising with regard to the application of microwave heating to the production of dye-sensitized solar cells on flexible polymer substrates.     

Synthesis and optical properties of V2O5 nanorods

A two-step method was proposed in synthesizing V2O5 nanorods on planar substrates, i.e., depositing a V2O3 thin film at approximately 220 degrees C (by heating a pure sheet of vanadium in a rough vacuum) and then heating it in air at approximately 400 degrees C. The V2O5 nanorods produced by this technique are single crystalline and could emit intense visible light at room temperature, possibly due to some defects such as oxygen vacancies which got involved during growth. This study provides a simple and low-substrate-temperature route in fabricating V2O5 nanorods on planar substrates, which might be also applicable to other metal oxides.     

Influences of Heating Condition and Substrate-Surface Roughness on the Characteristics of Sol-Gel-Derived Hydroxyapatite Coatings

A prepared transparent HA solution was coated on Ti6Al4V substrates by a spin-coating technique. The crystallization of the sol-gel-derived HA coated on the metallic substrates could be done at relatively low firing temperatures (as low as 600°C). The characteristics of the HA-coated layer were dependent on the surface roughness of substrates and heating conditions such as firing temperature, holding time, heating rate, and atmosphere. The heat treatment at a slow heating rate (<2°C/min.) and a long heating time (>10 hrs) at 600°C in air produced the uniform surface and improved the crystallinity. The HA layer coated on 20 m grit-blasted substates was more uniform and had fever cracks after firing, compared with that coated on 100 m grit-blasted rougher substrates.     

Rapid bonding of Pyrex glass microchips

A newly developed vacuum hot press system has been specially designed for the thermal bonding of glass substrates in the fabrication process of Pyrex glass microchemical chips. This system includes a vacuum chamber equipped with a high-pressure piston cylinder and carbon plate heaters. A temperature of up to 900 degrees C and a force of as much as 9800 N could be applied to the substrates in a vacuum atmosphere. The Pyrex substrates bonded with this system under different temperatures, pressures, and heating times were evaluated by tensile strength tests, by measurements of thickness, and by observations of the cross-sectional shapes of the microchannels. The optimal bonding conditions of the Pyrex glass substrates were 570 degrees C for 10 min under 4.7 N/mm(2) of applied pressure. Whereas more than 16 h is required for thermal bonding with a conventional furnace, the new system could complete the whole bonding processes within just 79 min, including heating and cooling periods. Such improvements should considerably enhance the production rate of Pyrex glass microchemical chips. Whereas flat and dust-free surfaces are required for conventional thermal bonding, especially without long and repeated heating periods, our hot press system could press a fine dust into glass substrates so that even the areas around the dust were bonded. Using this capability, we were able to successfully integrate Pt/Ti thin film electrodes into a Pyrex glass microchip.     

Evaporative characteristics of sessile nanofluid droplet on micro‐structured heated surface

Micro‐structure patterned substrates attract our attention due to the special and programmable wettabilities. The interaction between the liquid and micro/nano structures gives rise to controllable spreading and thus evaporation. For exploration of the application versatility, the introduction of nanoparticles in liquid droplet results in interaction among particles, liquid and microstructures. In addition, temperature of the substrates strongly affects the spreading of the contact line and the evaporative property. The evaporation of sessile droplets of nanofluids on a micro‐grooved solid surface is investigated in terms of liquid and surface properties. The patterned nickel surface used in the experiments is designed and fabricated with circular and rectangular shaped pillars whose size ratios between interval and pillars is fixed at 5. The behavior is firstly compared between nanofluid and pure liquid on substrates at room temperature. For pure water droplet, the drying time is relatively longer due to the receding of contact line which slows down the liquid evaporation. Higher concentrations of nanoparticles tend to increase the total evaporation time. With varying concentrations of graphite at nano scale from 0.02% to 0.18% with an interval at 0.04% in water droplets and the heating temperature from 22 to 85°C, the wetting and evaporation of the sessile droplets are systematically studied with discussion on the impact parameters and the resulted liquid dynamics as well as the stain. The interaction among the phases together with the heating strongly affects the internal circulation inside the droplet, the evaporative rate and the pattern of particles deposition.     

A dismantlable photoadhesion system fabricated by an anionic UV curing of epoxy resins with a base amplifier having a disulfide bond

A base amplifier (BA) that autocatalytically generates a diamine having a disulfide bond has been developed. Diamines generated from this BA are integrated into cross‐linked networks of epoxy resins that also have disulfide bonds. Anionic UV curing is performed using a photobase generator, the BA and the epoxy resins, and cured films are obtained after UV irradiation and subsequent heating at 160 °C. Furthermore, this curing system is applied successfully to adhesion of two stainless substrates, which is cancelled with gentle heating and a shear force. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 237–241     

Optical and Electrical Properties of Ferroelectric SBN Thin Films Prepared by Sol-Gel Process

Strontium barium niobate thin films were prepared by sol-gel method on various substrates using an improved process, two-step heating process. The two-step heating process applies an additive heat-treatment before crystallization for enhancement of the densification and the nucleation of films. Also, highly c-axis oriented SBN thin films with various compositions were obtained on MgO(100) and Pt(100)/MgO(100) substrates. Their optical and electrical properties such as optical propagation loss, refractive index, P-E hysteresis, and dielectric constant, were characterized as a function of the film composition.     

Resistance changes due to thermal coalescence in colloidal au/organic linker molecule multilayer films

A decrease in the resistance of colloidal Au multilayer films was observed upon heating. These multilayer Au films were fabricated by a layer-by-layer approach, using Au colloids and a bifunctional linker molecule, 1,6 hexanedithiol (HD) on polymer substrates. The resistance of the film prior to heating was 1 MOmega. The films were heated at three different temperatures, 120, 160, and 180 degrees C. After heating for 12 h, the resistance decreased by 6 orders of magnitude to about 50 Omega. This decrease in resistance was faster at higher temperatures. X-ray photoelectron spectroscopy (XPS) of the unheated films revealed two S 2p peaks corresponding to the Au-S thiolate peak and an oxidized S peak. Upon heating, the relative intensity of the oxidized S peak increased and that of the Au-S peak decreased, indicating an oxidation and desorption of the linker molecules. Scanning electron microscope (SEM) images of the heated films depict coalescence of the spherical Au particles into irregular shapes. The resistance decrease is believed to be due to the desorption of the linker molecule and subsequent coalescence of the Au particles. This method paves a way for controlling the resistance of electrodes on flexible polymer substrates.     

Synthesis of single-crystalline anatase nanorods and nanoflakes on transparent conducting substrates

Single-crystalline anatase nanorods and nanoflakes were grown on transparent conducting fluorine-doped tin oxide (FTO) substrates through hydrolysis of titanium tetrachloride (TiCl(4)) followed by heating to 450 °C.     

Microwave-accelerated cross-metathesis reactions of N-allyl amino acid substrates

Microwave heating has been utilised for the cross-metathesis reaction of N-allyl amino acid substrates to generate olefin homodimers. Remarkable acceleration of the cross-metathesis reaction (minutes compared to hours) over conventional reflux heating was observed. In addition, improved reaction yields and similar E/Z ratios for the cross-metathesis products were achieved.     

Synthesis of highly substituted indolines and indoles via intramolecular [4 + 2] cycloaddition of ynamides and conjugated enynes

Ynamides react with conjugated enynes in intramolecular [4 + 2] cycloadditions to afford substituted indolines that undergo oxidation with o-chloranil to furnish the corresponding indoles. The cycloaddition substrates are easily assembled from derivatives of 3-butynylamine by Sonogashira coupling with alkenyl halides followed by copper-catalyzed N-alkynylation with acetylenic bromides. Diynamides participate as particularly reactive 2pi components in the cycloaddition, providing access to indolines with carbon substituents at the C-7 position. Enynamides serve as 4pi components in a complementary version of the cycloaddition strategy which provides access to indoles and indolines substituted with carbon substituents at C-4. These enyne cycloadditions take place upon heating the substrates at 110-210 degrees C in toluene or 2,2,2-trifluoroethanol and in some cases can be achieved at 0 degrees C to room temperature in the presence of Lewis acids such as Me2AlCl.     

Biaryl and Aryl Ketone Synthesis via Pd‐Catalyzed Decarboxylative Coupling of Carboxylate Salts with Aryl Triflates

A bimetallic catalyst system has been developed that for the first time allows the decarboxylative cross‐coupling of aryl and acyl carboxylates with aryl triflates. In contrast to aryl halides, these electrophiles give rise to non‐coordinating anions as byproducts, which do not interfere with the decarboxylation step that leads to the generation of the carbon nucleophilic cross‐coupling partner. As a result, the scope of carboxylate substrates usable in this transformation was extended from ortho‐substituted or otherwise activated derivatives to a broad range of ortho‐, meta‐, and para‐substituted aromatic carboxylates. Two alternative protocols have been optimized, one involving heating the substrates in the presence of Cu^I/1,10‐phenanthroline (10–15 mol %) and PdI₂/phosphine (2–3 mol %) in NMP for 1–24 h, the other involving Cu^I/1,10‐phenanthroline (6–15 mol %) and PdBr₂/Tol‐BINAP (2 mol %) in NMP using microwave heating for 5–10 min. While most products are accessible using standard heating, the use of microwave irradiation was found to be beneficial especially for the conversion of non‐activated carboxylates with functionalized aryl triflates. The synthetic utility of the transformation is demonstrated with 48 examples showing the scope and limitations of both protocols. In mechanistic studies, the special role of microwave irradiation is elucidated, and further perspectives of decarboxylative cross‐couplings are discussed.     

TLC plates as a convenient platform for solvent-free reactions

Solvent-free oxidative couplings of naphthols have been optimized by co-spotting catalysts and substrates directly on silica TLC plates and heating, followed by chromatography, staining, and qualitative visualization.     

Microwave-assisted synthesis and antimicrobial activity of novel spiro 1,3,4-thiadiazolines from isatin derivatives

This work describes the synthesis of spiro 1,3,4-thiadiazolines from isatin-β-thiosemicarbazone acetylation, using microwave irradiation as a source of heating the reaction medium. N-substituted isatin derivatives were used as substrates to obtain thiosemicarbazones by adding thiosemicarbazide to the isatin ketone carbonyl. The final synthetic step was the reaction of thiosemicarbazones with acetic anhydride under microwave irradiation to get the spiro compounds. Reaction times ranged from 6 to 18 minutes resulting in yields of up to 90%. Biological assays have shown promising antibacterial and antifungal activity, especially spiro thiadiazolines derived from allylated isatins. All the proposed molecules proved to be potential drug candidates based on the results of the in silico investigation, with satisfactory drug-likeness and drug-score, respecting Lipinski's rule. The use of the microwave reactor was efficient for the synthesis of thiosemicarbazones and spiro compounds, resulting in a significant reduction in reaction times with conventional heating. Taking into account the threat of antimicrobial resistance, this work presents a series of bioactive molecules that are easily obtained via microwave reaction.     

Controlled nucleation and growth of thin hydroxyapatite layers on titanium implants by using induction heating technique

This paper reports the results obtained by the development of a new wet method of hydroxyapatite (HA) thin layer deposition. The method is based on the localized precipitation of HA on metallic substrates activated by induction heating. The technique developed has been shown to allow for the complete coating of substrates with micrometric thin films of HA within a low processing time. The method has been successfully applied to coat Ti plaques and Ti-6A1-4V cylinders.     

Multicomponent synthesis of imidazo[1,2-a]pyridines using catalytic zinc chloride

The novel use of zinc chloride to catalyze the one-pot, three component synthesis of imidazo[1,2-a]pyridines from a range of substrates using either conventional heating or microwave irradiation is described. This methodology affords a number of imidazo[1,2-a]pyridines in reasonable yields and short reaction times without any significant optimization of the reaction conditions.     

Observations on the use of microwave irradiation in azaheterocycle synthesis

A comparison of conventional heating and microwave irradiation in the synthesis of azaheterocycles is discussed. Microwave irradiation was found to increase the yields of the desired products, shorten the reaction times, and extended this chemistry to recalcitrant amide substrates and weak nucleophiles.