Solventless Synthesis Research Articles

Nanoparticles as curing and adhesive aid for biobased and petrobased polybenzoxazines

Alumina nanoparticles were incorporated in blends of benzoxazine monomers synthesized from bio- and petrobased phenols, cardanol and bisphenol A, respectively, by way of a one-pot solventless methodology. The structures of the monomers were characterized by proton (1H) nuclear magnetic resonance and Fourier transform infrared spectroscopy. Thermal characterization was performed using differential scanning calorimetry and thermogravimetry. The size of bare alumina nanoparticles and those in the polymer nanocomposite was analyzed by powder X-ray diffraction. Blending of alumina particles resulted in lowering of curing temperature of benzoxazine monomer. The effect of nanoparticle incorporation was reflected in the curing behavior and adhesive properties. The adhesive strength is found to be dependent on whether solution or solventless processing is used and on the weight percent of the nanoparticles in the monomer blend. The replacement of 75% bisphenol A content with cardanol in the benzoxazine resulted in a copolymer which showed a better or comparable adhesive strength. The adhesion was found to improve further with the incorporation of alumina nanoparticles. The lower viscosity of cardanol-based benzoxazine allowed both solventless synthesis and application of monomers, which is a way forward toward greener chemistry and low volatile organic compound processing strategies.

Catalytic performance of metal azolate frameworks in the solventless synthesis of cyclic carbonates from CO2 and epoxides

Two types of metal azolate frameworks (MAFs) with uncoordinated and coordinated nitrogen atoms composed of zinc coordinated with 3-amino-1,2,4-triazole and 3,5-dimethyl-1,2,4-triazole linkers denoted as MAF-66 and MAF-X5, respectively have been synthesized and characterized using various physicochemical techniques. The uncoordinated N donors present in the MAFs show high adsorption affinity for carbon dioxide. The synthesized MAFs showed promising catalytic activity towards the cycloaddition of carbon dioxide and epoxides under solvent-free conditions with excellent selectivity towards the desired five-membered cyclic carbonates. The importance of uncoordinated N donors and amine groups in the effective catalysis of the cycloaddition of CO2 and epoxides was investigated. Both catalysts were separable by simple filtration and reusable without any considerable loss in the initial activity. Various reaction parameters including temperature, reaction time, and CO2 pressure were studied. A possible reaction mechanism explaining the role of amine groups in the cycloaddition reaction was proposed based on literature and experimental inferences.

Solventless Synthesis of Poly(pyrazolyl)phenyl-methane Ligands and Thermal Transformation of Tris(3,5-dimethylpyrazol-1-yl)phenylmethane.

The solventless synthesis of tris(pyrazolyl)phenylmethane ligands of formula C6H5C(PzR2)3 (R = H, Me), starting from PhCCl3 and 3,5-dimethylpyrazole (PzMe2) or pyrazole (Pz) was performed. The sterically crowded C6H5C(PzMe2)3 is thermally transformed into the bis(pyrazolyl)(p-pyrazolyl)phenylmethane ligand PzMe2-C6H4CH(PzMe2)2. In this compound both PzMe2 rings are linked through the N-atom to the methine C-atom. At higher temperatures, the binding mode of PzMe2 changes from N1 to C4. All transformations occurred via quinonoid carbocation intermediates that undergo an aromatic electrophilic substitution on the 4-position of PzMe2. Reaction conditions were established to obtain five tris(pyrazolyl)phenylmethane ligands in moderate to good yields. 1H- and 13C-NMR spectroscopy and X-ray diffraction of single crystals support the proposed structures.

Cycloaddition of carbon dioxide with propylene oxide using zeolitic imidazolate framework ZIF-23 as a catalyst

Zeolitic imidazolate framework ZIF-23 was prepared and used as catalyst for the solventless synthesis of cyclic carbonate from CO2 and propylene oxide with or without TBAB co-catalyst. ZIF-23 catalysts were prepared by a solvothermal or microwave method and they were characterized by various physicochemical techniques such as XRD, FT-IR, BET, TGA, and FE-SEM. The effects of reaction parameters such as temperature, reaction time, CO2 pressure, and co-catalyst on the reactivity of catalyst were investigated. ZIF-23 was recyclable up to four times without any considerable loss of its initial activity. Reaction mechanism containing the role of ZIF-23 with TBAB co-catalyst was also proposed.

Solventless synthesis of AEL-type aluminophosphate molecular sieve from mechanochemically pretreated low-templated reactants

One of the main obstacles that hamper the application of zeolites is the high consumption of expensive structure-directing agent. Herein, we reported the mechanochemisty-mediated solventless synthesis of AlPO4-11 aluminophosphate molecular sieve with low dosage of diisopropylamine (DIPA) as the structure-directing agent. The influences of DIPA/Al2O3 ratio, fluoride ions, seed crystals and high-energy mechanochemical pretreatment on the synthesis of AEL-type zeolite were investigated in detail. Both DIPA and fluoride ions are indispensable for the successful synthesis of AEL phase. The resultant AEL molecular sieves were characterized by XRD, SEM, TG-DTA, CHN elements analysis, and N2 physisorption. The results indicate that the introduction of seed crystals cannot improve the phase purity and crystallinity of the resulting products. On the other hand, high-energy mechanochemical pretreatment not only can affect the morphology of AEL zeolite, but more importantly, can also reduce the consumption of structure-directing agent.

Facile room temperature solventless synthesis of high thermoelectric performance Ag2Se via a dissociative adsorption reaction

The facile room temperature yet solventless synthesis process, characterized by its simplicity, speed, low energy demand, low cost, opens a new avenue for the preparation of high quality silver chalcogenide samples.

Towards a global greener process: from solvent-less synthesis of molybdenum(vi) ONO Schiff base complexes to catalyzed olefin epoxidation under organic-solvent-free conditions

Schiff base ligands and corresponding molybdenum(vi) complexes, prepared using classical and/or mechanochemical methods, were active as epoxidation pre(catalysts).

Synthesis and evaluation of an efficient, durable, and environmentally friendly flame retardant for cotton

An efficient and durable formaldehyde-free flame retardant consisting of an ammonium salt of pentaerythritol tetraphosphoric acid (APTTP) was prepared by a solventless synthesis and characterized by Fourier-transform infrared (FT-IR) spectroscopy and nuclear magnetic resonance. The flame retardancy of the treated cotton fabric was enhanced, as assessed by limiting oxygen index (LOI), vertical flammability, and cone calorimetry measurements. The collected results demonstrated that cotton fabrics treated with APTTP exhibited high flame retardancy and excellent durability. Cotton fabric treated with a 140 g/L APTTP solution showed a LOI of 43.8%, and this value reduced to 26.9% after 50 laundering cycles. No after-flame and after-glow phenomena were presented during vertical flammability tests for all cotton fabrics treated with different concentrations of APTTP. Cone calorimetry results revealed a significant reduction in the intensity of the heat release rate and total heat release peaks. X-ray diffraction revealed that the crystalline particles of cotton fibers treated with APTTP were slightly affected compared with those of control sample. FT-IR spectroscopy results revealed that APTTP was grafted on the cotton fibers. Scanning electron microscopy showed that the surface of the treated cotton fibers remained smooth, while thermogravimetric analysis confirmed that the treated cotton fibers easily decomposed to form char. It was proposed that the flame retardant mechanism of APTTP occurred in the condensation phase.

Catalytic performance of zeolitic imidazolate framework ZIF-95 for the solventless synthesis of cyclic carbonates from CO2 and epoxides

The catalytic potential of a chloro-functionalized zeolitic imidazolate framework ZIF-95 was investigated for the solventless cycloaddition of carbon dioxide with epoxides. The reaction parameters were optimized and moderate set of reaction conditions (80°C and 1.2MPa CO2 pressure) were chosen for the detailed catalytic study. Eventhough ZIF-95 alone was catalytically active at higher temperatures, the addition of a co-catalyst was found beneficial to bring down the temperature required to achieve high conversions of the substrate. The synergistic effect of the catalyst and the co-catalyst was explored through the investigation of reaction mechanism. The scope of extending the catalysis for other epoxides was verified. The catalyst was successfully recovered and reused for cycloaddition up to 4 cycles.

Solventless synthesis of solketal with commercially available sulfonic acid based ion exchange resins and their catalytic performance

Abstract As a means to valorize glycerol, the synthesis of solketal through a ketalization reaction with acetone was performed. Mild solventless conditions were applied to test the activity of different commercially available sulfonic ion exchange resins that had already been used for other applications, namely: Amberlyst 35dry, Amberlyst 36dry, Purolite CT275DR, Purolite CT276 and Lewatit GF101. Thorough characterization of the resins is herein provided and discussed, including acidity, elemental analysis, thermogravimetric, 13C-NMR, surface area and pore size distribution measurements. Lewatit GF101 showed the best performance reaching a yield to solketal of 47% after 6 h of operation at 313 K using a molar excess of acetone to glycerol of 4.5 to 1, owing to a greater availability of active centers as well as the ease of access to them than in the rest of the resins. Additionally, reutilization with and without regeneration was performed in up to five cycles, showing that Purolite CT276 had the lowest relative drop of its maximum activity, despite being the least active in each of the cycles.

Solventless synthesis of m-LaVO4 photocatalyst for the degradation of methylene blue and textile effluent

Lanthanum vanadate (LaVO4) nanoplates with monoclinic (m) phase were synthesized by a facile solventless method. Lanthanum nitrate and ammonium metavanadate was used as precursors in this method. X-ray diffraction pattern reveals the monoclinic phase of LaVO4 (m-LaVO4). In addition, average grain size and lattice parameters were also calculated. Fourier transform infrared (FT-IR) analysis confirms the presence of La–O and V–O bonds in the sample. Optical property of m-LaVO4 nanoplates was estimated by DRS UV–visible and photoluminescence spectroscopy. HR-TEM (high resolution-transmission electron microscopy) analysis predicts the formation of LaVO4 nanoplates. Furthermore, m-LaVO4 nanoparticles were utilized as photocatalyst for the photodegradation of methylene blue (MB) dye under visible light illumination. m-LaVO4 photocatalyst showed substantial efficiency for the photodegradation of textile effluent (TE) within 120 min of visible light irradiation.

Solventless Synthesis of Quaterphenyls and Terphenyls from Chalcones and Allylsulfones under Phase Transfer Catalysis Conditions

Easily available chalcones and allyl sulfones along with cheap solid NaOH and polyethyleneglycol (PEG) 1000 have been used to directly generate the meta-terphenyl or quaterphenyl motifs under Phase Transfer Catalysis solventless conditions. The new approach provides an economic and environmentally friendly solution to removal of hazardous bases as well as organic solvents.

Solid-State Thermal Reaction of a Molecular Material and Solventless Synthesis of Iron Oxide

Solid-state thermal decomposition reaction of a molecular material $$\{\hbox {As}(\hbox {C}_{6}\hbox {H}_{5})_{4}[\hbox {Fe}^{\mathrm{II}}\hbox {Fe}^{\mathrm{III}} (\hbox {C}_{2}\hbox {O}_{4})_{3}]\}_{\mathrm{n}}$$ has been studied using non-isothermal thermogravimetry (TG) in an inert atmosphere. By analyzing the TG data collected at multiple heating rates in 300 K–1300 K range, the kinetic parameters (activation energy, most probable reaction mechanism function and frequency factor) are determined using different multi-heating rate analysis programs. Activation energy and the frequency factor are found to be strongly dependent on the extent of decomposition. The decomposed material has been characterized to be hematite using physical techniques (FT-IR and powder XRD). Particle morphology has been checked by TEM. A solid-state reaction pathway leading the molecular precursor to hematite has been proposed illustrating an example of solventless synthesis of iron oxides utilizing thermal decomposition as a technique using innocuous materials.

ChemInform Abstract: Silica‐Grafted Basic Amino Acids as Environmentally Benign Catalysts for the Solventless Synthesis of Cyclic Carbonates from Epoxides and CO2 under Metal‐Free and Halide‐Free Conditions.

AbstractSilica‐supported L‐histidine efficiently catalyzes the solvent‐free reaction of epoxides from styrene and terminal alkenes with carbon dioxide to the cyclic carbonates in high yields.

Solventless synthesis of a Schiff base that forms highly fluorescent organic nanoparticles exhibiting aggregation-induced emission in aqueous media

ABSTRACTA highly fluorescent solid state Schiff base compound (DBD) was synthesised using a green, solventless and fast approach in 30 sec. DBD shows almost no emission in THF solution, while it emits strong fluorescence in both dispersed nano-aggregates in the solution and as a powder, through a phenomenon known as aggregation-induced emission. Organic nanoparticles of DBD were prepared in aqueous solution using the nanoreprecipitation method with and without stabilizers. The nanoparticles exhibited strong, blue emission when the non-ionic surfactant, like triton X-100, was used as a stabilizer, and strong green emission when no surfactant or the cationic surfactant, like CTAB as a stabilizer was used. Using atomic force microscopy and dynamic light scattering, the sizes of the nanoparticles were found to be around 75 nm when prepared without surfactant, 50 nm when prepared using triton X-100, and 30 40 nm when prepared using CTAB. DBD nanoparticles show an emission maximum at 527 nm (pure green) in the cases of CTAB and no surfactant, while 400 nm emission is observed when triton X-100 is used. Finally, for practical applications, the new type of highly fluorescent organic nanoparticles (DBD) were chosen for on/off fluorescence switching nano sensor for detecting organic vapour.

Solventless Synthesis of MOFs at High Pressure

Besides the substitution or minimization of the use of harmful solvents, one essential goal of chemistry is to try to avoid their use altogether whenever possible. In the case of the synthesis of MOFs (metal–organic frameworks), this can only be achieved by finding alternatives to conventional processes. An example is the approach described here which involves working at high pressure (at 0.31 GPa) without using a solvent. This has evident advantages over mechanochemical synthesis by grinding or milling (also a solventless process) where the sample is submitted to attrition. The present paper reports the simple high pressure synthesis of the ZIF (zeolitic imizadolate framework) ZIF-8. This methodology enables fast synthesis of MOF materials and offers new insights into their industrial implementation. In addition, this technique could be applied to the synthesis of other MOFs and even COFs (covalent organic frameworks).

Applying Mechanochemistry for Bottom-Up Synthesis and Host-Guest Surface Modification of Semiconducting Nanocrystals: A Case of Water-Soluble β-Cyclodextrin-Coated Zinc Oxide.

Mechanochemistry has recently emerged as an environmentally friendly solventless synthesis method enabling a variety of transformations including those impracticable in solution. However, its application in the synthesis of well-defined nanomaterials remains very limited. Here, we report a new bottom-up mechanochemical strategy to rapid mild-conditions synthesis of organic ligand-coated ZnO nanocrystals (NCs) and their further host-guest modification with β-cyclodextrin (β-CD) leading to water-soluble amide-β-CD-coated ZnO NCs. The transformations can be achieved by either one-pot sequential or one-step three-component process. The developed bottom-up methodology is based on employing oxo-zinc benzamidate, [Zn4 (μ4 -O)(NHOCPh)6 ], as a predesigned molecular precursor undergoing mild solid-state transformation to ZnO NCs in the presence of water in a rapid, clean and sustainable process.

Solventless synthesis of new 4,5-disubstituted 1,2,3-selenadiazole derivatives and their antimicrobial studies

AbstractTwo novel, namely 5-Phenyl-4-methyl-1, 2, 3-selenadiazole (5h) and 4-Phenyl-5-propyl-1, 2, 3-selenadiazole (5i) along with several other aliphatic and aromatic series of 1,2,3-selenadiazoles were synthesized at room temperature in one step under solventless conditions from the corresponding semicarbazones. All compounds were thoroughly characterized by various spectroscopic tools. The synthesized new and reported 1,2,3-selenadiazoles were found active against bacterial as well as fungal stains when screened for their antimicrobial activity against various pathogenic bacteria and fungi using agar disc diffusion as well as agar well diffusion method. Almost all selenadiazoles showed better antibacterial properties in comparison to established antibiotics like tetracycline. 4-ethyl-5-methyl-1,2,3-selenadiazole showed higher antimicrobial activity amongst the tested selenadiazoles.

High performance bio-based benzoxazine networks from resorcinol and hydroquinone

This work presents a scalable and solventless synthesis of two fully bio-based bis-benzoxazine resins derived from resorcinol, hydroquinone and furfurylamine. The structures of the two synthesized precursors have been studied by 1H NMR and FTIR spectroscopies and SEC. The polymerization and degradation of the precursors have been investigated and monitored by DSC and TGA. The properties of the resulting polybenzoxazine networks were found to be dependent on the precursor molecular structure. In both cases, an excellent thermomechanical behavior associated with high charring ability were obtained which highlights the great potential of these fully bio-based resins as new matrices for the preparation of structural composites following a sustainable approach.

Silica-Grafted Basic Amino Acids as Environmentally Benign Catalysts for the Solventless Synthesis of Cyclic Carbonates from Epoxides and CO2 under Metal-Free and Halide-Free Conditions

A series of basic amino acids immobilized onto solid supports that can play cooperative roles was developed and applied as environmentally benign catalytic systems for the solventless synthesis of cyclic carbonates from epoxides and carbon dioxide under metal-free and halide-free conditions. The highest yield of styrene carbonate was achieved with silica supported l -histidine, associated with the acidic nature of silica: Si–OH groups on the silica surface act as a weak acid to activate the epoxide for the synergetic effect with the basic amino acid. The influence of various reaction parameters on catalytic activity was investigated. Moreover, the catalyst exhibited good recyclability.