Ring-Opening Polymerization of Siloxanes Using Phosphazene Base Catalysts

Selective, Catalytic Oxidations of C–H Bonds in Polyethylenes Produce Functional Materials with Enhanced Adhesion

Solid base catalysts: fundamentals and their applications in organic reactions

Amino-modified Merrifield resins as recyclable catalysts for the safe and sustainable preparation of functionalized α-diazo carbonyl compounds

H2 production from methane pyrolysis over commercial carbon catalysts: Kinetic and deactivation study

This paper reviews various types of heterogeneous acid-base catalysts for fragrances preparation. Catalytic activities of various types of heterogeneous acid and base catalysts in fragrances preparation, i.e. non-zeolitic, zeolitic, and mesoporous molecular sieves have been reported. Generally, heterogeneous acid catalysts are commonly used in fragrance synthesis as compared to heterogeneous base catalysts. Heteropoly acids and hydrotalcites type catalysts are widely used as heterogeneous acid and base catalysts, respectively. © 2013 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0)

Synthesis of TiO2-polymer nanocomposite in supercritical CO2 via RAFT polymerization

A series of biodegradable poly (glycerol-sebacate-l-lactide) (PGSLA) copolymers, with variable PLLA length, were synthesized and characterized. The copolymers comprised PGS backbone chain with a nominal molecular weight of 2,800 g/mol. The length of each PLLA side chain covered the 800–14,000 range, while the length of the PLLA was easily controlled by the feed molar ratio of the l-lactide to the PGS. The structure of the copolymer was studied by nuclear magnetic resonance spectroscopy and gel permeation chromatography. Differential scanning calorimetric measurements and thermal gravimetric analysis had been performed to indicate the glass transition temperature (T g), melting point (T m), and the degree of crystallinity (χ c). It was also found that the onset decomposition temperature (T d) of the copolymers was lower than those of the linear polylactide (LPLLA). After solution casting and solvent evaporation, porous structures were found in the copolymer films by scanning electron microscope (SEM). Water contact angle results showed that the hydrophilicity of the copolymers was much higher than that of linear PLLA. In vivo, PGSLA copolymer demonstrated a favorable tissue response profile compared to PGS/LPLLA blend. There was also significantly less inflammation and fibrosis during degradation. PGSLA might therefore serve as an excellent candidate material for medical applications, given its minimal in vivo tissue response.

In the present work, nonporous hydrophilic unmodified silica aerogel was synthesized successfully by ambient drying with one step base catalyst by used silica organic initiator tetraethoxysilane (TEOS). Silica aerogel was prepared twice by sol-gel technique; the first one was the gelation that happened under the alkaline catalyst NH4OH, which has a toxic property and dangerous to human health. The second gelation under the effect of the safety inorganic base catalyst sodium silicate (water glass) that used as an inorganic low-cost and environmentally friendly initiator to silica, plays a role in increasing pH as a catalyst and as a new rare co-precursor mixing organic and inorganic silica precursors (TEOS+Na2SiO3). The impurities accompanying water glass and sodium residue were eliminated by a lot of washing. The volume ratio of the (TEOS: ethanol: H2O: base catalyst) fixed respectively at (5.6:50:10:0,01M). The gelation reaction time, the gel properties, it's quality and the amount of the reactant, the density, and the appearance all effect by the type of catalyst used. The comparative study of silica porous aerogel production properties diagnostic achieved by FTIR, XRF, BET, BJH, FESEM and thermal conductivity applied as insulation materials .

Hyperbranched polyurethane (HBPU) elastomers were synthesized from dimer fatty acid-ethylene glycol polyester diol (DFA-EG), toluene diisocyanate (TDI) and glycerol (GLY) by a two-step, solvent-free process. The effect of glycerol on phase separation was studied by Fourier transforminfrared (FT-IR) and differential scanning calorimetry (DSC). The thermal and viscoelastic properties of the HBPU were investigated by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA), respectively. The transparent HBPU elastomers presented a typical amorphous morphology, with a single glass transition temperature (Tg) about -25 °C. All TGA curves showed two distinct stages of degradation with the onset decomposition temperature at 275 °C. It was found that the increasing content of GLY resulted in a decrease in the thermal stability between 295 °C and 445 °C. The results for DMA revealed that HBPU crosslinked with GLY had high elasticity up to 5.12 MPa at 100 °C. The best mechanical and viscoelastic properties were achieved at the nNCO(TDI)/nOH(DFA-EG+GLY) of 0.95, with its hardness and tensile strength values of 83 A and 13.2 MPa, respectively and the storage modulus value of 32.8 MPa. In addition, the lowest water absorptivity was 0.24% when the nNCO(TDI)/nOH(DFA-EG+GLY) equalled 1.05.

Sulfide solid electrolytes are expected to be used for practical all solid-state batteries because they combine high formability with high ionic conductivity. However, unlike oxide and organic solid electrolytes, sulfide solid electrolytes have problems such as toxic hydrogen sulfide generation and conductivity degradation due to even slight moisture. In this study, we investigated the details of the denaturation of argyrodite-type sulfide solid electrolyte (ASSE) by a small amount of water, with the aim of further increasing the water resistance of ASSE. The denaturation of ASSE in air with moisture at the dew point −20 °C, which is comparable to a typical dry room environment, was already reported; EIS and XRD revealed only the surface of ASSE degraded by moisture in the air. Surface analysis was also conducted and revealed that surface degraded components such as Li2CO3, Li2SO4 are formed on the surface.In this study, the effects of oxygen and carbon dioxide were also examined in addition to water. Details of the denaturation was investigated using XRD, XPS, IR and Raman. This investigation revealed that the denaturant is formed only on the surface by moisture, that the denaturant is oxidized by oxygen, and that Li2CO3 is formed by carbon dioxide. More details will be discussed at the meeting site.

Imidazolium-type basic ionic liquids (BILs), including 1-butyl-3-methyl imidazolium hydroxide ([Bmim][OH]), 1-butyl-3-methyl imidazolium phosphate ([Bmim][PO4]), 1-butyl-3-methyl imidazolium carbonate ([Bmim][CO3]), and 1-butyl-3-methyl imidazolium bicarbonate ([Bmim][HCO3]), coordinated by iron chloride (FeCl3·6H2O), were used as both the ligand and catalyst in activators generated by the electron transfer ATRP (AGET ATRP) of methyl methacrylate (MMA) in bulk and solution, without the use of traditional ligands (such as 2,2-bipyridine, tetrabutylammonium bromide, and tetra-n-butylphosphonium bromide). Catalytic amounts of BILs could enhance the initiator efficiency (0.87–0.91) and the polymerization rate, and produce PMMA with controllable molecular weights and narrow molecular weight distributions (Mw/Mn = 1.20–1.40). The nature of the controlled/“living” free radical polymerization in the presence of BILs was confirmed by chain-extension experiments. The ready solubility and availability of BILs enable them to be applied as a new type of ligand and catalyst in iron-mediated AGET ATRP.

Naphthalene-containing polyimides: Synthesis, characterization and photovoltaic properties of novel donor-acceptor dyes used in solar cell

The ylide 4‐picolinium, p ‐chloro phenacylide‐initiated thermal polymerization of ethyl methacrylate (EMA) was studied. 4‐Picolinium p ‐chloro phenacylide induces the thermal polymerization of ethyl methacrylate at 65°C. The rate of polymerization ( R p ) rose as the initiator concentration increased from 2 × 10 −3 to 4 × 10 −3 M and the initiating exponent was computed as 1.9. The R p decreased as the concentration of ylide increased from 6 × 10 −2 to 1 M . The greater initiator concentration also affected the molecular weight inversely. The polymerization was carried out at different temperatures and the overall activation energy was computed as 4.08 Kcal/mol. Polymerization was inhibited in the presence of hydroquinone as a radical scavenger. Kinetic studies and other data show that the overall polymerization takes place in a radical mechanism. The various kinetic parameters, such as the rate and average degree of polymerization, molecular weight, and energy of activation of the present system, were evaluated.

Synthesis of cis- and trans-2-methoxy-3,4-epoxytetrahydropyrans (4) and (5), 3,4-anhydro-1,2-isopropylidene-β-DL-arabinopyranose (6), and the cis- and trans-2-methoxy-3,4-epoxytetrahydrofurans (7) and (S), which are carbohydrate-precursor oxirans, using a new procedure of oxiranation with peroxybenzimidic acid and potassium carbonate as the basic catalyst is described. The method has been extended to the oxiranation of several olefins such as indene (9), oct-1-ene (10), trans-β-methylstyrene (11), allyl alcohol (12), and chroman-4-one (13). In all cases, the method appears to be efficient and produces the oxirans in excellent yields after short reaction times.

Semi‐rigid polyurethane (PU) foams were prepared using lignin‐molasses‐ poly(ethylene glycol) polyols. Two kinds of lignin, kraft lignin (KL) and sodium lignosulfonate (LS), were used. Both lignin and molasses polyols were mixed with various ratios and were reacted with poly(phenylene methylene) polyisocyanate (MDI) in the presence of silicone surfactant and di‐n‐butyltin dilaurate. A small amount of water was used as a foaming agent. The apparent density of PU foams increased with increasing lignin content. The compression strength and elastic modulus linearly increase with increasing apparent density, suggesting that mechanical properties are controllable by changing reaction conditions. The PU foams were amorphous and glass transition was detected by differential scanning calorimetry. The glass transition temperature (Tg ) maintained an almost constant value, regardless of the mixing ratio. This indicates that both the phenolic group of lignin and the glucopyranose ring of molasses act as rigid components in PU crosslinking network structures, and both groups contribute to the main chain motion to the same extent. By thermogravimetry (TG), it was confirmed that PU foams are thermally stable up to around 300 °C. By differential scanning calorimetry, Tg was observed at temperatures from 80 to 120 °C.