Absence Of Solvent Research Articles

A Tailorable Family of Elastomeric‐to‐Rigid, 3D Printable, Interbonding Polymer Networks

AbstractSoft materials with widely tailorable mechanical properties throughout the material's volume can shape the future of soft robotics and wearable electronics, impacting both consumer and defense sectors. Herein, a platform of 3D printable soft polymer networks with unprecedented tunability of stiffness of nearly three orders of magnitude (MPa to GPa) and an inherent capability to interbond is reported. The materials are based on dynamic covalent polymer networks with variable density of crosslinkers attached to prepolymer backbones via a temperature‐reversible Diels–Alder (DA) reaction. Inherent flexibility of the prepolymer chains and controllable crosslinking density enable 3D printed networks with glass transition temperatures ranging from just a few degrees to several tens of degrees Celsius. Materials with an elastomeric network demonstrate a fast and spontaneous self‐healing behavior at room temperature both in air and under water—a behavior difficult to achieve with other crosslinked materials. Reversible dissociation of DA networks at temperatures exceeding ≈120 °C allows for reprintability, while control of the stereochemistry of DA attachments enables reprogrammable shape memory behavior. The introduced platform addresses current major challenges including control of polymer interbonding, enhanced mechanical performance of printed parts, and reprocessability of 3D‐printed crosslinked materials in the absence of solvent.

Practical Solvent‐Free Microwave‐Assisted Hydroboration of Alkynes

A simple and rapid protocol for the anti‐Markovnikov hydroboration of alkynes assisted by microwave irradiation has been developed. Pinacolborane smoothly reacts with terminal alkynes to obtain (E)‐alkenyl boronates in good yields and short reactions times in the absence of solvent. Further transformations on the carbon‐boron bond of the adducts can be sequentially achieved without the need of purifying the alkenyl boronates.

Matter-wave interference and deflection of tripeptides decorated with fluorinated alkyl chains.

Studies of neutral biomolecules in the gas phase allow for the study of molecular properties in the absence of solvent and charge effects, thus complementing spectroscopic and analytical methods in solution or in ion traps. Some properties, such as the static electronic susceptibility, are best accessed in experiments that act on the motion of the neutral molecules in an electric field. Here, we screen seven peptides for their thermal stability and electron impact ionizability. We identify two tripeptides as sufficiently volatile and thermostable to be evaporated and interfered in the long‐baseline universal matter‐wave interferometer. Monitoring the deflection of the interferometric molecular nanopattern in a tailored external electric field allows us to measure the static molecular susceptibility of Ala–Trp–Ala and Ala–Ala–Trp bearing fluorinated alkyl chains at C‐ and N‐termini. The respective values are 4πε0×330±150Å3 and 4πε0×270±80Å3.

Synthesis of Copper Sulfide Nanoparticles by Thermal Decomposition Approach and Morphology Dependent Peroxidase-Like Activity.

Copper sulfide nanoparticles have been employed as artificial mimics for peroxidase-like activity. In the present study, copper sulfide nanoparticles with four different morphologies have been synthesized by thermal decomposition of cyclo-tri-μ-thioacetamide-tris(chlorocopper(I)) complex ([Cu₃TAA₃Cl₃]) at 200 °C in different solvents such as diphenyl ether, ethylene glycol, 1-octadecene and also without any solvent. Hierarchical copper sulfide nanostructures are formed when the complex is decomposed in the absence of solvent, in diphenyl ether, and 1-octadecene while in the case of ethylene glycol, randomly agglomerated nanoparticles are formed. The precursor complex ([Cu₃TAA₃Cl₃]) as well as copper sulfide nanoparticles were characterized using an array of techniques and after characterization, the peroxidase-like activity of copper sulfide nanoparticles was investigated.Morphologically different copper sulfide nanoparticles possess different exposed facets and due to this, the peroxidase-like activity was different among different morphologies.

Optimization of the endodontic retreatment

Aim. Optimization of an endodontic retreatment by performing the following tasks, including the selection of an optimal and safe solvent.Materials and methods. In order to choose the most suitable solvent for the problem, an experiment was conducted with clove, mint, eucalyptus, orange, and grapefruit oils. The surface tension coefficient was measured by the Rebinder apparatus. In order to justify the choice of an effective essential oil, as well as the dissolving ability and the absence of solvent and debris after irrigation with sodium hypochlorite in the root canal, a tube-shaped electron scanning microscopy was performed.Results. Grapefruit oil has the most dissolving activity (p < 0.05). In addition to the solubility of the filler and siller, grapefruit essential oil is able to dissolve the smear layer.Conclusion. Optimization of the endodontic retreatment with root canals previously filled with gutta-percha, is possible using essential oils, however, a grapefruit oil is the most effective.

Solvent-Free Synthesis of Nano Zirconium Phenylphosphonates with Molten Phenylphosphonic Acid.

Nanosized α-zirconium phenylphosphonate particles were successfully prepared by the reaction between different zirconium sources and molten phenylphosphonic acid in the absence of solvent. The resultant nanoplates exhibit particle sizes in the range of 15 to 30 nm. The use of a topotactic anion exchange method starting from α-zirconium phosphate instead resulted in the generation of 15 to 180 nm plates, while also resulting in nanoparticles with a higher degree of crystallinity. The topotactic anion exchange of the phosphate groups by phenylphosphonate groups could be performed to completion when performed in molten phenylphosphonic acid. Characterization of both the final products as well as the individual steps in the anion exchange were performed by powder XRD, fast neutron activation analysis, TGA, FTIR spectroscopy, TEM, solid-state NMR and XPS.

Introduction of a new catalyst containing an ionic liquid bridge on nanoporous Na+- montmorillonite for the synthesis of hexahydroquinolines and 1,8-dioxo-decahydroacridines via Hantzsch condensation

A new nanoporous catalyst formulated as Na+-MMT-[bip]-NH2+ HSO4− is prepared via modification of Na+-MMT with bis-3-(trimethoxysilylpropyl)-amine and then addition of sulfuric acid. In continue the prepared reagent is identified with different methods including Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), energy dispersive spectrometer (EDS) and CHN elemental analysis. After identification the catalytic efficiency of this reagent is tested in the synthesis of hexahydroquinolines and 1,8-dioxo-decahydroacridines via Hantzsch condensations. All reactions are performed under mild conditions in the absence of solvent in high yields in short reaction times. The catalyst is also reusable for several times in both of the studied reactions.

A multifaceted biomimetic interface to improve the longevity of orthopedic implants

The rise of additive manufacturing has provided a paradigm shift in the fabrication of precise, patient-specific implants that replicate the physical properties of native bone. However, eliciting an optimal biological response from such materials for rapid bone integration remains a challenge. Here we propose for the first time a one-step ion-assisted plasma polymerization process to create bio-functional 3D printed titanium (Ti) implants that offer rapid bone integration. Using selective laser melting, porous Ti implants with enhanced bone-mimicking mechanical properties were fabricated. The implants were functionalized uniformly with a highly reactive, radical-rich polymeric coating generated using a unique combination of plasma polymerization and plasma immersion ion implantation. We demonstrated the performance of such activated Ti implants with a focus on the coating's homogeneity, stability, and biological functionality. It was shown that the optimized coating was highly robust and possessed superb physico-chemical stability in a corrosive physiological solution. The plasma activated coating was cytocompatible and non-immunogenic; and through its high reactivity, it allowed for easy, one-step covalent immobilization of functional biomolecules in the absence of solvents or chemicals. The activated Ti implants bio-functionalized with bone morphogenetic protein 2 (BMP-2) showed a reduced protein desorption and a more sustained osteoblast response both in vitro and in vivo compared to implants modified through conventional physisorption of BMP-2. The versatile new approach presented here will enable the development of bio-functionalized additively manufactured implants that are patient-specific and offer improved integration with host tissue. Statement of SignificanceAdditive manufacturing has revolutionized the fabrication of patient-specific orthopedic implants. Although such 3D printed implants can show desirable mechanical and mass transport properties, they often require surface bio-functionalities to enable control over the biological response. Surface covalent immobilization of bioactive molecules is a viable approach to achieve this. Here we report the development of additively manufactured titanium implants that precisely replicate the physical properties of native bone and are bio-functionalized in a simple, reagent-free step. Our results show that covalent attachment of bone-related growth factors through ion-assisted plasma polymerized interlayers circumvents their desorption in physiological solution and significantly improves the bone induction by the implants both in vitro and in vivo.

Synthesis and characterization of Fe3O4@SiO2@(CH2)3NH(CH2)2O2P(OH)2 and its catalytic application in the synthesis of benzo-[h]quinoline-4-carboxylic acids via a cooperative anomeric based oxidation mechanism

In this study, Fe3O4@SiO2@(CH2)3NH(CH2)2O2P(OH)2 as a new and recoverable nanocatalyst with magnetic properties was synthesized. The characterization of the novel nanocatalyst confirmed by thermo gravimetric analysis/ differential thermal analysis (TGA/DTA), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM) equipped by energy dispersive spectroscopy (EDS), elemental mapping analysis, Fourier transform infrared (FT-IR) spectroscopy and vibrating sample magnetometer (VSM). The impact of Fe3O4@SiO2@(CH2)3NH(CH2)2O2P(OH)2 was carefully considered in the synthesis of benzo-[h]quinoline-4-carboxylic acids via a three component reaction of aryl aldehydes, naphtylamine, and pyrovic acid in the absence of solvent. The suggested mechanism proposed an anomeric based oxidation route for final step of the described synthesis. The described catalyst was recycled and reused without any remarkable decrease in the yield and the reaction time after six runs.

Vat photopolymerization of liquid, biodegradable PLGA-based oligomers as tissue scaffolds

Additive manufacturing (AM) of tissue scaffolds provides medical professionals and patients with personalized treatment options, which align with patients’ specific physiology and provide a more efficient and precise manufacturing process. Vat photopolymerization (VP) AM affords biocompatible, degradable, and high-resolution scaffolds capable of achieving specific pore sizes necessary for tissue regeneration. Earlier biodegradable, photoactive polymers for the VP platform usually require dissolution in a solvent or water, which often results in anisotropic shrinkage upon drying and inconsistencies in the final part geometry. This work describes a photoactive oligomeric precursor that eliminates the requirement for water or solvent during VP. Poly(lactide-co-glycolide) (PLGA) diacrylates with low number-average molecular weights (< 1400 g mol−1) provided liquid, viscous precursors. Upon crosslinking, the networks exhibited mechanical strength and low cytotoxicity, which are prerequisites for soft tissue scaffolds. Systematically varying the ratios of lactide to glycolide provided a range of degradation rates from 4 to 12 wks. Tailored degradation rates will enable use in different anatomical environments. Cytotoxicity and cell attachment studies revealed crosslinked films that promoted cell growth and proliferation. This manuscript describes an expanded polymer toolbox for AM of tissue scaffolds with precise resolution in the absence of solvents.

Polycarbosilane-Grafted Nanoparticles: Free-Flowing Hairy Nanoparticle Liquids That Convert to Ceramic

Here, we report a new class of hybrid nanoparticles (NPs) that are self-supporting and display viscous flow behavior in the absence of solvent, yet convert to a purely inorganic material on heating...

Aerobic synthesis of N-sulfonylamidines mediated by N-heterocyclic carbene copper(I) catalysts.

A new catalytic strategy for the one-pot synthesis of N-sulfonylamidines is described. The cationic copper(I) complexes were found to be highly active and efficient under mild conditions in air and in the absence of solvent. A copper acetylide is proposed as key intermediate in this transformation.

Ultrafast Intersystem Crossing in Isolated Ag29(BDT)123- Probed by Time-Resolved Pump-Probe Photoelectron Spectroscopy.

The photophysics of the isolated trianion Ag29(BDT)123- (BDT = benzenedithiolate), a ligand-protected cluster comprising BDT-based ligands, terminating a shell of silver thiolates and a core of silver atoms, was studied in the gas phase by femtosecond time-resolved, pump-probe photoelectron spectroscopy. UV excitation at 490 nm populates one or more singlet excited states with significant charge transfer (CT) character in which electron density is shifted from shell to core. These CT states relax on an average time scale of several hundred femtoseconds by charge recombination to yield either the vibrationally excited singlet ground state (internal conversion) or a long-lived triplet (intersystem crossing). Our study is the first ultrafast spectroscopic probe of a ligand-protected coinage metal cluster in isolation. In the future, it will be interesting to study how cluster size, overall charge state, or heteroatom doping can be used to tune the corresponding relaxation dynamics in the absence of solvent.

Facile and solvent-free synthesis of a novel bio-based hyperbranched polyester with excellent low-temperature flexibility and thermal stability

In this work, a novel biobased hyperbranched polyester (HBPE) with excellent low-temperature flexibility (low Tg) and thermal stability, was prepared from the self-polycondensation of AB2 monomer based on methyl ricinoleate (MR), a commercially available derivative from castor oil. The AB2 monomer was facilely synthesized by UV-initiated thiol-ene addition between MR and 2-mercaptoethanol in the absence of solvents. The reaction parameters were systematically optimized, and the highest yield up to 98 % was achieved with almost complete conversion of double bond within 2 h. A series of HBPEs were then obtained via bulk polymerization of the AB2 monomer under different conditions. Among the four transesterification catalysts investigated, Ti(OBu)4 was demonstrated to be the most efficient one due to the higher polymerization efficiency and molecular weight (Mn = 13,000∼17,000 g/mol) of as-obtained HBPEs. And the degree of branching (DB) was estimated to be in the range of 0.30∼0.42. Notably, the HBPEs with dangling chains exhibited a low glass transition temperature (Tg) of ―42.8∼―59.2 °C, indicative of excellent low-temperature flexibility. TGA results indicated that the onset thermal degradation temperature under nitrogen exceeded 310 °C for all the HBPEs. In comparison to the polyrincinoleate as a linear polyester analogue, the HBPE behaved like Newtonian fluid behaviors with lower complex viscosities.

Isoniazid-functionalized Fe3O4 Magnetic Nanoparticles as a Green and Efficient Catalyst for the Synthesis of 3, 4-dihydropyrimidin-2(1H)-ones and their Sulfur Derivatives.

A wide variety of dihydropyrimidins (DHPMs) exhibit pharmacological and biological activities. Herein, an efficient one-pot synthesis of some 3, 4-dihydropyrimidin-2(1H)-one derivatives is reported using Fe3O4 @SiO2-Pr-INH. Recently, several catalysts have been used to improve the Biginellis-reaction. However, some of these catalysts have imperfections. Herein, a convenient method for the synthesis of 3, 4-dihydropyrimidin- 2(1H)-ones and their sulfur derivatives using Fe3O4 @SiO2-Pr-INH is reported. Firstly, the catalyst was synthesized through a simple four-step method. The Fe3O4 MNPs were synthesized using the chemical co-precipitation method, coated with a layer of silica using TEOS, and then functionalized with CPTMS. Subsequently, a nucleophilic substitution of Cl by isoniazid resulted in the formation of the magnetic Fe3O4@SiO2-Pr-INH. After the preparation and characterization of Fe3O4@SiO2-Pr-INH, its catalytic activity was studied in the synthesis of 3, 4-dihydropyrimidin-2(1H)-one derivatives. Following the optimization of the reaction conditions, several 3, 4-dihydropyrimidin-2(1H)-one derivatives were synthesized by the reaction of ethyl acetoacetate or acetylacetone, thiourea or urea and aromatic aldehydes at 80 °C under solvent-free conditions. Isoniazid-functionalized Fe3O4 magnetic nanoparticles (Fe3O4@SiO2-Pr-INH) were prepared using Fe3O4 with silica layer and their surface was modified with isoniazid. They were characterized successfully by infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy and were used for the synthesis of some 3, 4-dihydropyrimidin-2(1H)-one derivatives as catalysts. Aromatic aldehydes with electron-donating or electron-withdrawing groups afforded 3, 4- dihydropyrimidin-2(1H)-ones and their sulfur derivatives in good to excellent yields in short reaction times. Isoniazid-functionalized Fe3O4 magnetic nanoparticles (Fe3O4@SiO2-Pr-INH) were used as an efficient catalyst for Biginelli-type synthesis of 3, 4-dihydropyrimidin-2(1H)-ones and 3, 4-dihydropyrimidin- 2(1H)-thiones in good to excellent yields and short reaction times. It is noteworthy that this method has several advantages such as simple experimental procedures, the absence of solvent, environmentally benign process, stability and reusability of the catalyst.

New efficient tetraphenyl silylated poly(azomethine)s based on “pincer-like” bis(imino)pyridine iron(III) complexes as heterogeneous catalysts for CO2 conversion

Aromatic poly(azomethine)s containing simultaneously for the first time both tetraphenyl silane moeties and “pincers” of bis(imino)pyridine were prepared, to provide these polymers with a robust structure and ability to anchor metals. The polymers were prepared from difunctional monomers which provide an special conformation yielding moderate surface areas (up to 60 m2/g). The insolubility and further incorporation of iron to these polymers have generated a new set of heterogeneous catalysts with high metal content, high thermal stability and with excellent catalytic performance in the cycloaddition of CO2 to epoxides to form cyclic carbonates. Very small amounts of catalysts work efficiently, in the absence of solvent, at moderate CO2 pressures (3 bar) showing very high yields of epoxide conversion (up to 95%), 100% of selectivity to the corresponding cyclic carbonate in all cases and high turn-over numbers (up to 7000) being reused at least five times with no apparent loss in catalytic activity. The new catalysts are more efficient than a similar catalyst previously reported for this conversion and work in milder conditions.

Highly selective Co3O4/silica-alumina catalytic system for deoxygenation of triglyceride-based feedstock

The catalytic deoxygenation of biomass to produce renewable carbon energy addresses major concerns of limited energy sources. In particular, the second-generation biodiesel by selective deoxygenation possesses a higher cetane number, lower cloud point, and higher oxidation stability compared to the fatty acid ester-based biodiesel, and therefore, can be fed directly to the current diesel engines. In present work, we address the significant concerns of cost-effectiveness, high hydrodeoxygenation (HDO) selectivity, modest hydrogen environments, and solvent-free condition using high surface area silica-alumina-supported cobalt oxide nanoparticles as a catalyst to produce fuel-grade hydrocarbons from fatty acid-based feeds that are palm oil and jatropha oil. The catalytic performance is tested for methyl stearate to achieve the best conversion efficiency with remarkable deoxygenation selectivity. The HDO selectivity was as high as 87% at 250 °C and 30 bar H2 pressure, whereas moderate HDO selectivity with relatively higher cracking was observed at 300 °C and 2 bar H2 pressure. Remarkably, the HDO selectivity was comparable in the absence of solvent. The catalyst is recyclable with low metal leaching during the deoxygenation. The use of non-noble metal catalysts under solvent-free conditions offers facile production of fuel-grade hydrocarbons.

Enzymatic synthesis of benzyl benzoate using different acyl donors: Comparison of solvent-free reaction techniques

In this study, benzyl benzoate was successfully synthesized via enzymatic acylation using three immobilized enzymes as biocatalysts. Different acyl donors (benzoic acid and benzoic anhydride), operation regimes (batch, fed-batch), mixing modes (conventional mechanical stirring and ultrasound), process parameters (temperature, substrate molar ratio of acyl donor to acyl acceptor), presence or absence of solvents, enzyme amount and type were evaluated. Benzoic acid is a solid that is difficult to solubilize and, thus, was not efficient as acyl donor for the synthesis of benzyl benzoate. On the other hand, benzoic anhydride was very effective for the acylation of benzyl benzoate, and the presence of an excess of benzyl alcohol was essential to ensure the solute-solvent intermolecular attractions and good substrate solubilization, allowing the ester synthesis to be performed in the absence of organic solvents. The ultrasound was effective in increasing increase the initial reaction rate and the final conversion (88 %). However, the Lipozyme TL-IM and RM-IM supports were damaged, and the reuse was unfeasible. The batch and fed-batch approaches in conventional stirring ensured high conversions of 92 and 90 %, respectively, for batch (anhydride: alcohol 1:6) and fed-batch (1:3) using the Lipozyme TL-IM as biocatalyst. The controlled addition of the anhydride (fed-batch) allowed the reduction of alcohol molar ratio but decreased the reaction rates, and the maximum conversions were reached only after 24 h, while the batch approach had 92 % of conversion after 6 h. The yield of benzyl benzoate was high at 6 wt.% of enzyme, low temperature (50 °C), and simple reactor operation (batch). Results show the feasibility of the synthesis of benzyl benzoate via acylation using a green process that may be an alternative route to the chemical synthesis.

The use of a microchannel reactor for optimizing the production of 1-alkyl-3-methylimidazolium chlorides

The possibility to use microchannel flow reactors for obtaining kinetic and technological parameters of the synthesis of 1-butyl-3-methylimidazolium chloride (BMIMCl) ionic liquid was demonstrated for the reaction of 1-methylimidazole (MIm) with 1-chlorobutane in the absence of solvents. BMIMCl was produced with high selectivity and specific output in a microchannel flow reactor at temperatures 120–180 °C and contact times 2-45 min at a pressure of 20 bar. The positive result is obtained due to the laminar profile of the flow and a uniform distribution of the reagents’ concentration over the microchannel cross-section. Investigation of the process kinetics in a microchannel flow reactor made it possible to reveal that the reaction moves to the diffusion resistance mode at a temperature above 150 °C. The kinetic data obtained for the BMIMCl synthesis were used to develop methods for the production of 1-ethyl-3-methylimidazolium and 1-hexyl-3-methylimidazolium chlorides (EMIMCl and HMIMCl, respectively) under the conditions of a microchannel flow reactor. The approach suggested in this paper is of interest for the development of flow and batch setups for a small-tonnage production of dialkylimidazolium, ammonium and pyridinium salts by quaternization of the corresponding alkyl chlorides and nitrogen-containing bases.

Phenylalanine-based ionic liquid crystals with water-induced phase transition behaviors

l-Phenylalanine (L-Phe) and d-phenylalanine (D-Phe) were chosen as chiral sources to interact with 1-tetradecyl-3-methylimidazolium hydroxide (C14mimOH). Two ionic liquid crystals (ILCs), [C14mim][L-Phe] and [C14mim][D-Phe], were prepared. Both of the two ILCs exhibit good thermostability and can self-assemble to a smectic A (SmA) mesophase in a pretty wide temperature window (from ~−20 °C to ~105 °C) in the absence of solvents. When water is introduced, the ILCs show rich lyotropic phase behaviors. With the increasing water content, the ILCs transformed from the SmA mesophase to a cubic Ia3d and then to a Im3m mesophase, eventually producing precipitates composed of numerous flat fibers. The rheological properties including mechanical strength and viscosity of the ILCs exhibited temperature- and water content-dependent changes. The ILCs inherited the chirality of the amino acids well. This work proposes a simple one-step self-assembly method to construct natural biomolecule-based chiral materials, providing potential applications in chiral amplification and selectors of chiral extraction or molecule detection.