Synthesis of ammonia in high-frequency discharges

The synthesis of ammonia from nitrogen-hydrogen plasma prepared using radiofrequency discharge and microwave discharge was studied under the same experimental conditions except the driving frequency. Twice larger amounts of ammonia were adsorbed on zeolite used as adsorbent in the microwave discharge than in the radiofrequency discharge. Relative intensities of NH band head (A³–X^3–,0–0) as well as hydrogen atomic line (H\) observed in the plasma prepared using microwave discharge were one order of magnitude larger than those in the plasma prepared using radiofrequency discharge. Since NH_x radicals and H atoms are considered ammonia precursors, the advantage of microwave discharge over radiofrequency discharge on ammonia synthesis is discussed from the results obtained above and from the plasma parameters,kT _e andn _e , obtained by the electric double probe technique.Partly presented at the 8th International Symposium on Plasma Chemistry, August 31 to September 4, 1987, Tokyo, Japan.     

Lipase‐Catalyzed Degradation of Polyester in Supercritical Carbon Dioxide

Enzymatic degradation of poly(ε‐caprolactone) has been successfully carried out in supercritical carbon dioxide (scCO₂). Candida antarctica lipase smoothly catalyzed the hydrolytic degradation in scCO₂ to give oligo(ε‐caprolactone). The degradation in the presence of acetone (5 vol.‐%) produced the oligomer of smaller molecular weight (less than 500) compared to that prepared without the additive. Matrix‐assisted laser desorption/ionization‐time of flight (MALDI‐TOF) mass spectrometry analysis showed that the degradation product was of a mixture of linear and cyclic oligomers. The addition of a very small amount of water also promoted the degradation of the polyester.     

Soluble polyphenol

Soluble polyphenol was synthesized for the first time by enzymatic oxidative polymerization of phenol using peroxidase and hydrogen peroxide as catalyst and oxidizing agent, respectively. A mixed solvent of alcohol and buffer improved the polymer solubility toward N,N-dimethylformamide (DMF). The resulting polymer was composed of a mixture of phenylene and oxyphenylene units. Changing the solvent composition could control the molecular weight and regioselectivity of the polymer. The polymer was found to possess relatively high thermal stability.     

Laccase-catalyzed polymerization of acrylamide

Enzymatic polymerization of acrylamide was carried out in water. Laccase, a copper-containing oxidoreductase derived from Pycnoporus coccineus, induced the polymerization at relatively low temperature (50°C) to give a polymer of high molecular weight. In the presence of 2,4-pentanedione, laccase efficiently mediated the vinyl polymerization at room temperature.     

Oxidative polymerization of p-alkylphenols catalyzed by horseradish peroxidase

Enzymatic oxidative polymerization of p-alkylphenols using horseradish peroxidase as catalyst has been carried out in two polymerization solvent systems: a mixture of phosphate buffer (pH 7) and 1,4-dioxane, and a reverse micellar solution, yielding powdery polymeric materials. The polymer yield was much dependent upon the type of alkyl group in the monomer as well as the solvent type. In case of the polymerization of umbranched alkylphenols in the aqueous 1,4-dioxane, the polymer yield increased with increasing chain length of the alkyl group from 1 to 5, and the yield of the polymer from hexyl or heptylphenol was almost the same as that of the pentyl derivative. The relationship between the type of substituent and the polymer yield in the reverse micellar system was different from that in the aqueous 1,4-dioxane; the highest yield was achieved from ethylphenol. The resulting polymers had molecular weight of several thousands. The polymer was estimated to be composed from a mixture of phenylene and oxyphenylene units from IR analyses. TG measurement exhibited that the polymer had relatively high thermal stability. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1453–1459, 1997     

Involvement of the γ Isoform of cPLA2 in the Biosynthesis of Bioactive N-Acylethanolamines

Arachidonylethanolamide (anandamide) acts as an endogenous ligand of cannabinoid receptors, while other N-acylethanolamines (NAEs), such as palmitylethanolamide and oleylethanolamide, show analgesic, anti-inflammatory, and appetite-suppressing effects through other receptors. In mammalian tissues, NAEs, including anandamide, are produced from glycerophospholipid via N-acyl-phosphatidylethanolamine (NAPE). The ɛ isoform of cytosolic phospholipase A₂ (cPLA₂) functions as an N-acyltransferase to form NAPE. Since the cPLA₂ family consists of six isoforms (α, β, γ, δ, ɛ, and ζ), the present study investigated a possible involvement of isoforms other than ɛ in the NAE biosynthesis. Firstly, when the cells overexpressing one of the cPLA₂ isoforms were labeled with [¹⁴C]ethanolamine, the increase in the production of [¹⁴C]NAPE was observed only with the ɛ-expressing cells. Secondly, when the cells co-expressing ɛ and one of the other isoforms were analyzed, the increase in [¹⁴C]N-acyl-lysophosphatidylethanolamine (lysoNAPE) and [¹⁴C]NAE was seen with the combination of ɛ and γ isoforms. Furthermore, the purified cPLA₂γ hydrolyzed not only NAPE to lysoNAPE, but also lysoNAPE to glycerophospho-N-acylethanolamine (GP-NAE). Thus, the produced GP-NAE was further hydrolyzed to NAE by glycerophosphodiesterase 1. These results suggested that cPLA₂γ is involved in the biosynthesis of NAE by its phospholipase A₁/A₂ and lysophospholipase activities.     

Enzymatic synthesis and curing of biodegradable crosslinkable polyesters

The lipase-catalyzed synthesis and curing of polyesters that possess an unsaturated fatty acid moiety in the side chain is described. Lipase-catalyzed polymerization of divinyl sebacate and glycerol in the presence of unsaturated fatty acids produced a crosslinkable polyester possessing the unsaturated group. Candida antarctica lipase showed high catalytic activity for their synthesis. Effects of reaction parameters, such as enzyme amount, temperature, and feed ratio of substrates, have been systematically investigated. The polymerization under reduced pressure improved the polymer yield and molecular weight. Divinyl adipate was also enzymatically polymerized with glycerol and linoleic acid to give the crosslinkable polyester. The polymer obtained using linoleic or linolenic acid, was cured using a cobalt naphthenate catalyst or thermal treatment to give a crosslinked, transparent, polymeric film with a high-gloss surface. The cured film was characterized by pencil-scratch hardness testing and FT-IR spectroscopy. The biodegradability of the obtained film was evaluated by biochemical oxygen demand (BOD) measurement in an activated sludge.

     

Lipase-catalyzed polycondensation of dicarboxylic acid–divinyl esters and glycols to aliphatic polyesters

Lipase-catalyzed polymerization of dicarboxylic acid–divinyl esters with glycols has been performed. The vinyl esters used were divinyl adipate and divinyl sebacate. Lipases derived from Candida antarctica, Mucor miehei, Pseudomonas cepacia, and P. fluorescens showed high catalytic activity toward the present polymerization. Effects of solvent, reaction temperature, and enzyme amount were systematically investigated. A combination of divinyl adipate, 1,4-butanediol, and P. cepacia lipase afforded the highest molecular weight (2.1 × 10⁴). The yield of the polymer from divinyl sebacate was higher than that from divinyl adipate, whereas the opposite tendency was observed in the polymer molecular weight. Methylene chain length of α,ω-alkylene glycol also affected the polymerization behavior. The enzymatic polymerization of divinyl sebacate with cis-2-butene-1,4-diol and 2-butyne-1,4-diol resulted in the polymer containing unsaturated group in the polymer backbone. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2737–2745, 1999     

Synthesis and curing behavior of alkyl-substituted poly(aryl ether ketone)s having a crosslinkable styryl group at chain ends

Crosslinkable alkyl-substituted poly(aryl ether ketone)s (PEKs) bearing a styryl group at both chain ends were synthesized by nucleophilic substitution reaction of 1,1′-(p-phenyl-enedioxy)bis[2-methyl-4-(4-fluorobenzoyl)benzene] with an excess aromatic diol in the presence of a base, followed by the reaction of the terminal phenol group with chloromethylstyrene. The aromatic diols used in this study were hydroquinone and resorcinol. The molecular weight of the polymer determined by GPC and ¹H NMR agreed with each other and close to the theoretical value calculated from the feed ratio. The polymer was soluble in N,N-dimethylacetamide and tetrahydrofuran, but insoluble in acetone and methanol. From DSC analysis, the polymer was thermally crosslinked around 220°C. The addition of dicumyl peroxide as a radical generator in the polymer decreased the curing temperature. The cured polymer showed high thermal stability up to 420°C under nitrogen. © 1997 John Wiley & Sons, Inc.