Synthesis and characterization of Ce–La oxides for the formation of dimethyl carbonate by transesterification of propylene carbonate

A series of cerium–lanthanum catalysts prepared using the co-precipitation method were investigated for transesterification of propylene carbonate (PC) with methanol to produce dimethyl carbonate (DMC). Synthesized catalysts were characterized by XRD, CO₂- and NH₃-TPD, N₂ adsorption/desorption and SEM–EDX techniques. Studies were carried out to study the effect of reaction conditions such as methanol/PC molar ratio (4–12), catalyst dose (2–10 wt.% of PC), reaction time (2–10 h) and temperature (140–180 °C) on the DMC yield. Highest PC conversion and DMC yield of 72% and 74%, respectively, were observed with catalysts having a 1:4 Ce/La molar ratio.     

Investigation on a green synthetic approach for glycerol carbonate： The reaction of glycerol with urea

以甘油和尿素为原料,探讨了低甘油含量的甘油碳酸酯环境友好的合成工艺。考察了催化剂的结构、反应条件等因素对甘油转化率的影响,结果表明在390 ℃煅烧3 h的硫酸锌催化效果最好。采用甘油与尿素反应后再与碳酸酯反应的偶合反应方式,所得甘油碳酸酯中甘油的含量仅为0.6%,降低了合成成本。     

Chemicals from biomass: Synthesis of glycerol carbonate by transesterification and carbonylation with urea with hydrotalcite catalysts. The role of acid–base pairs

Synthesis of glycerol carbonate has been performed by transesterification of ethylene carbonate with glycerol catalyzed by basic oxides (MgO, and CaO), and mixed oxides (Al/Mg, Al/Li) derived from hydrotalcites. The results showed that the optimum catalyst in terms of activity and selectivity is a strong basic Al/Ca-mixed oxide (AlCaMO) which is able to catalyze the reaction at low temperature (35 °C), and low catalyst loading (0.5 wt%) giving high glycerol conversions with 98% selectivity to glycerol carbonate. When the synthesis of glycerol carbonate was carried out by carbonylation of glycerol with urea, the results showed that balanced bifunctional acid–base catalysts where the Lewis acid activates the carbonyl of the urea and the conjugated basic site activates the hydroxyl group of the glycerol were the most active and selective catalysts.     

Synthesis and characterization of a new polymer–drug conjugate with pH-induced activity

A well-defined, stimuli-responsive tetrapolymer with pH-responsive characteristics and targeting specificity has been synthesized by radical copolymerization of methacrylic acid, N-(2-hydroxypropyl)methacrylamide, methacryloyl glycylglycyl sulfamethoxazole, and N-(methacryloyl)glycylglycine 4-nitrophenyl ester. The structure and properties of tetrapolymer were investigated by NMR, FT-IR, UV–visible absorption, TEM and gel permeation chromatography. Incorporation of maleimide linker into tetrapolymer facilitates its conjugation with antibody fragments, as demonstrated by the solid-phase immunoassay experiments. The TEM image shows that tetrapolymer had self-assembled a spherical micelle with a diameter ranging from 50 to 150 nm. Altering the pH of the solution leads to a different extent of aggregation at pH 6.5–3.5, responding in accordance with the properties associated with the extracellular environment of solid tumors and endocytosis. Furthermore, fluorescence spectroscopy indicated a critical micelle concentration (CMC) of 1 mg/mL. Because of the solvation and ionization effects, the tetrapolymer showed considerably enhanced antibacterial activities against Escherichia coli in the presence of DMSO and the antibacterial activity increased with decreasing pH value.     

All-cellulose films with excellent strength and toughness via a facile approach of dissolution–regeneration

This study describes a green method for preparing all-cellulose nanocomposites through a dissolution and regeneration process. Cotton linter pulp was dissolved in 7 wt % NaOH/12 wt % urea aqueous solution precooled to −12°C. Self-assembly of cellulose molecules into nanostructured cellulose fiber is achieved by using water addition and controlling the temperature to regenerate cellulose. By changing the microenvironment of the cellulose solution, the morphology of the nanostructured cellulose fibers and the mechanical properties of the regenerated cellulose films can be tuned. Then, a series of regenerated cellulose films have been prepared and characterized from various aspects. Compared with other all-cellulose films in the literature, the regenerated all-cellulose nanocomposite films prepared in this work exhibited good optical transparency, thermal stability, and excellent tensile strength (up to 135 MPa) when the regeneration temperature was adjusted to 50°C. This work provided a green and promising approach to prepare high-performance and environmentally friendly all-cellulose nanocomposites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46925.     

Synthesis of magnetic mesoporous silica composites via a modified Stöber approach

In this work, magnetic Fe₃O₄@mesoporous silica composites were synthesized by a microemulsion (oil-in-water/ethanol) approach which was applied with a modified Stöber reaction. Cetyl trimethyl ammonium bromide was employed as the surfactant, nano-Fe₃O₄ particles were dispersed in microemulsion. Tetraethyl orthosilicate (TEOS) formed oil drops, and ammonia solution facilitated the hydrolysis polymerization of TEOS. The diameters of the magnetic Fe₃O₄@mesoporous silica composites can be tuned within the range 120–380 nm by varying the ratio of ethanol/water and the amount of nano-Fe₃O₄ particles. Brunauer–Emmett–Teller surface areas of magnetic Fe₃O₄@mesoporous silica composites were determined to be within the range 490–759 m²/g and their pore sizes were around 2.3 nm as it was determined by Barrett–Joyner–Halenda method. Furthermore, the encapsulation of poorly water-soluble drugs within magnetic Fe₃O₄@mesoporous silica composites was investigated using protoporphyrin IX. Magnetic Fe₃O₄@mesoporous silica composites showed a drug loading within 22–68 mg/g, which can be an excellent drug delivery platform for photodynamic therapy.     

Synthesis and surfactant properties of a new “extended” glucidoamphiphile made from D-glucose

We prepared a new nonionic surfactant, 8, in which the n-dodecyl chain is attached at the C-3 carbon of the D-glucose-based glucopyranose moiety by the linkage Z=?O-(α-PP-O) _n with ?O-(α-PP-O) _n being a commercial poly-(α-propyloxy) oligomeric mixture (with average ñ=6). This amphiphilic behavior study showed that, when compared to the reference compound 3-O-dodecyl-D-glucopyranose (Z=O), compound 8 exhibits (i) a water solubility that is 100-fold higher, (ii) a hydrophilic-lipophilic balance value increase from 8.5 to 12.6 units, and (iii) a slighly lower critical micelle concentration.     

A new and efficient catalytic system for synthesis of diphenyl carbonate with W–Mo-heteropolyacids as a cocatalyst

A new catalytic system, which consists of Pd(OAc)₂ as the catalyst and W–Mo-containing heteropolyacids (HPAs)/Mn(OAc)₂ as the bicomponent cocatalysts, has been found to be very efficient in the oxidative carbonylation of phenol to diphenyl carbonate at low pressure in the absence of solvent. The efficiency of the catalytic system is dependent on the ratio of W/Mo in the HPAs, being best in a ratio of 6/6. The synergistic effect between W–Mo-containing HPAs and Mn(OAc)₂ has been observed in the catalysis. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis of σ Receptor Ligands with a Spirocyclic System Connected with a Tetrahydroisoquinoline Moiety via Different Linkers

With the aim to develop new σ₂ receptor ligands, spirocyclic piperidines or cyclohexanamines with 2-benzopyran and 2-benzofuran scaffolds were connected to the 6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline moiety by variable linkers. In addition to flexible alkyl chains, linkers containing an amide as functional group were synthesized. The 2-benzopyran and 2-benzofuran scaffold of the spirocyclic compounds were synthesized from 2-bromobenzaldehyde. The amide linkers were constructed by acylation of amines with chloroacetyl chloride and subsequent nucleophilic substitution, the alkyl linkers were obtained by LiAlH₄ reduction of the corresponding amides. For the development of σ₂ receptor ligands, the spirocyclic 2-benzopyran scaffold is more favorable than the ring-contracted 2-benzofuran system. Compounds bearing an alkyl chain as linker generally show higher σ affinity than acyl linkers containing an amide as functional group. A higher σ₁ affinity for the cis-configured cyclohexanamines than for the trans-configured derivatives was found. The highest σ₂ affinity was observed for cis-configured spiro[[2]benzopyran-1,1′-cyclohexan]-4′-amine connected to the tetrahydroisoquinoline system by an ethylene spacer (cis- 31 , K_i (σ₂)=200 nM; the highest σ₁ affinity was recorded for the corresponding 2-benzofuran derivative with a CH₂C=O linker (cis- 29 , K_i (σ₁)=129 nM).     

Synthesis and characterization of pyrrole and thiophene functional polystyrenes via “click chemistry”

Novel side-chain pyrrole or thiophene functional polystyrenes (PS-Py and PS-Th) were synthesized by using ‘‘click chemistry’’ strategy. First, approximately 40% of chloro groups of poly(styrene-co-chloromethylstyrene) P(S-co-CMS), prepared by nitroxide mediated radical polymerization (NMRP), were converted to azido groups by using NaN₃ in N,N-dimethylformamide. Propargyl pyrrole was prepared by etherification of 4-(1H-pyrrol-1-yl)phenol prepared by Clauson-Kaas reaction using propargylbromide. Propargyl thiophene was synthesized by heterogeneous esterification reaction between 3-thiophenecarboxylic acid and propargylbromide. Finally, azido-functionalized polystyrene was coupled to these propargyl functional heterocyclics with high efficiency by click chemistry. The intermediates at various stages and final polymers were characterized by spectral analysis and cyclic voltammetry.     

Synthesis and properties of acrylate functionalized alkyds via a Diels–Alder reaction

The α-eleosterate pendent fatty acid of a tung oil based alkyd was functionalized via a Diels–Alder reaction with three different acrylate groups: (1) 2,2,2-trifluoroethyl methacrylate, (2) 3-methacryloxypropyl trimethoxysilane, and (3) triallyl ether acrylate. The modified alkyds were characterized by using ¹H NMR, ¹³C NMR, and gel permeation chromatography (GPC). The drying time was measured at ambient temperature. The viscoelastic properties of the alkyd-modified films were measured using dynamic mechanical thermal analysis. The viscoelastic and drying time results show that the alkyd modified with siloxane and triallyl group affords a faster drying time, higher crosslink density, and higher glass transition temperature compared to the unmodified alkyd, whereas the fluorinated alkyd possesses surface active properties, but suffers in terms of drying and crosslinking density.     

Synthesis of a novel organic–inorganic hybrid flame retardant based on Ca(H2PO4)2 and hexachlorocyclotriphosphazene and its performance in polyvinyl alcohol

To optimize the poor thermal stability and flammable of polyvinyl alcohol (PVA), a novel environmental-friendly organic–inorganic hybrid flame retardant Ca(H₂PO₄)₂@HCCP was successfully designed and synthesized via surface treatment technology and used to advance the flame retardancy of PVA. The thermogravimetric analysis implied that Ca(H₂PO₄)₂@HCCP can enhance significantly the thermal stability and char forming ability of PVA. Combustion results demonstrate that Ca(H₂PO₄)₂@HCCP could effectively suppress the melt dripping of PVA in the process of combustion. The presence of Ca(H₂PO₄)₂@HCCP can sharply reduce peak heat release rate and the total heat release up to 75% and 22.9%, respectively, in the microscale combustion calorimeter measurement. The results manifested that Ca(H₂PO₄)₂@HCCP could endow PVA with superior flame retardancy. Moreover, char residues analysis explained the flame retardant mechanism in condensed and gas phase, which is mainly attributed to the strong catalytic char formation, free radical trapping, and gas barrier effect. Therefore, the green flame retardant has great applications prospect in fire safety.     

Synthesis and characterization of a new binuclear cobalt complex containing μ-acetamidino-μ-amido-μ-nitrito-bridged groups via an intramolecular condensation

Condensation of coordinated acetonitrile and one of the amine ligands in [(NH₃)₄Co·μ(NH₂,NO₂)·Co(NH₃)₄](CF₃SO₃)₄. H₂O (2c) results in the formation of a bridging acetamidino group. It is assumed that an intramolecular reaction occurred in which a coordinated amido ligand attack the substituted acetonitrile group to yield the third bridge. In this process the amido and acetonitrile groups which are coordinated to adjacent cobalt centers should bear a syn relationship. Synthesis and characterization of [(NH₃)₃Co·μ(CH₃C(NH)₂,NH₂,NO₂)·Co(NH₃)₃](CF₃SO₃)₃ (5) is reported here.     

“Click” Synthesis and Redox Activity of a Water-Soluble Triazolylcobalticinium Polyelectrolyte

Ionic macromolecules, i.e. polyelectrolytes are of academic and industrial interest due to their poly-charged structures and applications. Here a polyelectrolyte containing redox-active cobalticinium groups is synthesized by Cu^I-catalyzed azide alkyne Huisgen-type regioselective 1,3-cycloaddition, which is also-called “click” synthesis between a poly(azidomethylstyrene) polymer and ethynylcobalticinium. Overall, this first triazolylcobalticinium polymer is easily prepared in only three steps, which opens the way for applications such as redox sensing in aqueous media, polymer encapsulation of hydrophobic biomedical molecules in water and stabilization of colloidal suspensions. Cyclic voltammetry shows chemically and electrochemically reversible reductions on the electrochemical time scale, to the neutral 19-electron cobaltocene polymer and to the unstable 20-electron anionic structure. Application of Bard’s equation using the decamethylferrocene reference allows estimating that the number of electrons transferred in the first cyclic voltammetry wave is 29 ± 3, close to the number of cobalticinium units, 31 ± 2, determined by size exclusion chromatography.     

Synthesis and Surface Properties of Dicephalic Surfactants with a 1,3-Dioxane Ring

A new group of surface active dicephalic derivatives of 1,3-dioxane, i.e., 2-alkyl-5,5-bis{[3-(N,N-dimethylamino)propyl]amido}-1,3-dioxane-di-N-oxides, were synthesized with high yields by the reaction of an appropriate 2-alkyl-5,5-bis-(carboxyethyl)-1,3-dioxane with an excess of N,N-dimethyl-1,3-propanediamine followed by oxidation with an aqueous solution of hydrogen peroxide. Structures and purity of all intermediates and final di-N-oxides were confirmed by means of ¹H-NMR and ESI-MS spectroscopy. Synthesized compounds showed high surface activity with low values of critical micelle concentration and high effectiveness of surface tension reduction (γ _CMC). However, only derivative with the longest 2-alkyl substituent showed good foaming and moderate emulsifying properties.

Synthesis of a stable and porous Co–B nanoparticle catalyst for selective hydrogenation of cinnamaldehyde to cinnamic alcohol

The Co–B nanoparticle catalyst supported on TiO₂ for the selective hydrogenation of cinnamaldehyde to cinnamic alcohol was prepared by a modified electroless plating method. The as-prepared catalyst was characterized by X-ray diffraction and transmission electron microscope. The results showed that porous Co–B nanoparticles were distributed narrowly (40–45 nm) over the support. Compared with the Co–B nanoparticles prepared by chemical reduction of Co²⁺ ions with borohydride, the as-resulted Co–B nanoparticles were stable to be stored in air, and exhibited higher activity and selectivity of cinnamic alcohol in cinnamaldehyde hydrogenation.     

Synthesis and characterization of mesoporous ZnTiO3 rods via a polyvinylpyrrolidone assisted sol–gel method

Mesoporous ZnTiO₃ rods were fabricated via a polyvinylpyrrolidone assisted sol–gel method. In this method, the control of nanostructure growth was achieved by the cooperative assembly among precursors and polyvinylpyrrolidone, through which well-designed one-dimensional morphology and mesoporosity could be obtained. The regularity of rod-like morphologies was sensitive to cooperative assembly temperature. Furthermore, the mesoporous ZnTiO₃ rods were used for photodegradation of organic dyes and proved to be useful photocatalysts with excellent reusability thanks to the well-designed nanostructure and one-dimensional structure. Hence mesoporous ZnTiO₃ rods with good photocatalytic activity and low cost could offer broad opportunities for environmental remediation.     

Synthesis and properties of highly branched poly(urethane–imide) via A2 + B3 approach

A series of highly branched poly(urethane–imide) (HBPUI) were synthesized via A₂ + B₃ approach using isophorone diisocyante (IPDI), polycarbonatediol (PCDL), 3,3′,4,4′-Benzophen-onetetracarboxylic dianhydride (BTDA), and poly(oxyalkylene) triamine (ATA) as materials. The structure of the products was characterized by FT-IR and ¹³C-NMR. The molecular weights were characterized by gel permeation chromatograph (GPC). The solution viscosity, thermal, and mechanical properties were measured by rotational rheometer, differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), tensile tests, and dynamic mechanical analysis (DMA), respectively. The HBPUI showed lower viscosity than that of linear poly(urethane–imide) (LPUI), nevertheless T _g of HBPUI was higher than that of LPUI. TGA indicated that the thermal degradation of poly(urethane–imide) occurred above 300 °C, which was higher than conventional polyurethane. The tensile strength of HBPUI was obviously improved by increasing the content of BTDA and the molar ratio of [A₂]/[B₃]. The effects of the content of BTDA and the molar ratio of [A₂]/[B₃] on the storage modulus of the polymers were also studied.