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Takeshi Endo - One of the best experts on this subject based on the ideXlab platform.

  • selective gas solid phase fixation of carbon dioxide into oxirane containing polymers synthesis of polymer bearing cyclic Carbonate Group
    Green Chemistry, 2006
    Co-Authors: Bungo Ochiai, Tokinori Iwamoto, Takeshi Endo
    Abstract:

    Gas–solid phase fixation of carbon dioxide into oxirane-containing polymers proceeds selectively without concomitant crosslinking reactions, which have previously been unavoidable due to the dense arrangement of oxirane Groups. The fixation reaction obeys first-order kinetics, supporting the selectivity of the reaction.

  • self polyaddition of six membered cyclic Carbonate having fmoc protected amino Group novel synthetic method of polyhydroxyurethane
    Macromolecules, 2001
    Co-Authors: Hidetoshi Tomita, Fumio Sanda, Takeshi Endo
    Abstract:

    This article deals with the self-polyaddition of 3-(1,3-dioxan-2-one-5-yl)propyl 2-(9-fluorenylmethoxycarbonylamino)ethyl thioether by the deprotection of the 9-fluorenylmethyoxycarbonyl (Fmoc) Group with N,N-diisopropylethylamine, 4-(dimethylamino)pyridine, or triethylamine as a novel synthetic method of a polyhydroxyurethane. The polymer with higher yields and Mn's was obtained by using N,N-diisopropylethylamine and 4-(dimethylamino)pyridine than triethylamine. Fmoc deprotection and stability of the cyclic Carbonate Group were elucidated to optimize the condition by using the model compounds, 3-cyclohexylpropyl 2-(9-fluorenylmethoxycarbonylamino)ethyl thioether and 3-(1,3-dioxan-2-one-5-yl)propyl ethyl thioether.

  • Polymer reaction of epoxide and carbon dioxide. Incorporation of carbon dioxide into epoxide polymers
    Macromolecules, 1995
    Co-Authors: Tadashi Sakai, Nobuhiro Kihara, Takeshi Endo
    Abstract:

    Polymeric epoxides can be converted to corresponding five-membered cyclic Carbonates effectively by the reaction with carbon dioxide. For instance, poly(glycidyl methacrylate) (PGMA) was quantitatively converted to a polymethacrylate bearing a five-membered cyclic Carbonate Group (PDOMA) by the polymer reaction with carbon dioxide using alkali metal or quaternary ammonium halide salt as a catalyst. The salts having more Lewis acidic cation and more nucleophilic anion acted as more effective catalysts. Kinetic analyses of the polymer reaction show that the reaction rate can be expressed by the empirical equation : -d[epoxide]/dt = k[epoxide][catalyst] m , where m depends on the Lewis acidity of the catalyst and molecular weight of the epoxide. The rate of the reaction is independent of the pressure of carbon dioxide. Further, various polymeric epoxides such as GMA copolymers, poly(glycidyl acrylate), and poly(vinylbenzyl glycidyl ether) could be converted to the corresponding polymers bearing five-membered cyclic Carbonate moieties by the reaction with carbon dioxide, whereas the presence of an aromatic Group in the structure of the polymer could retard the reaction with carbon dioxide.

  • Model reactions of functionalization of polyCarbonate. Reactions of phenyl chloroformate with nucleophiles and cationic polymerization behavior of bicyclo orthoesters containing Carbonate Group
    Journal of Polymer Science Part A: Polymer Chemistry, 1990
    Co-Authors: Hitomi Uno, Akihiko Nakazawa, Toshikazu Takata, Takeshi Endo
    Abstract:

    Some model experiments for functionalization of a polyCarbonate were carried out. At first, reactivity of phenyl chloroformate with a few nucleophiles was examined. Reaction with alkyl amines gave corresponding carbamates, but in the case of aniline, formation of a byproduct diarylurea was observed. Reactions with alcohols and phenols afforded Carbonates in moderate yields, in which p-nitrophenol and isopropyl alcohol were less reactive. On the basis of these results, 1-ethyl-4-phenoxycarboxymethyl-2,6,7-trioxabicyclo[2.2.2]octane (2) and 1-ethyl-4-ethoxycarboxymethyl-2,6,7-trioxabicyclo[2.2.2]octane (3) were prepared by the reaction of phenyl and ethyl chloroformates with 1-ethyl-4-hydroxymethyl-2,6,7-trioxabicyclo[2.2.2]octane in the presence of tert-amine. 2 polymerized cationically with BF3OEt2 at more than 80°C to give a polyether containing both ester and Carbonate Groups in the side chain, with contamination of a gelled polymer.

Feng-chih Chang - One of the best experts on this subject based on the ideXlab platform.

  • The reactivity of epoxy/polyCarbonate/BF_3-MEA system
    Journal of Polymer Research, 2001
    Co-Authors: Ye-shiu Li, Feng-chih Chang
    Abstract:

    The cationic reaction of an epoxy/BF_3-MEA system occurs between the oxirane Group and the oxonium Group. The addition of polyCarbonate to the system does not cause a transesterification reaction between the Carbonate Group and the oxonium Group, thus the molecular weight of the PC is unchanged during the reaction. PC crystallization is observed in the cured system because the epoxy monomer accelerates the PC crystallization. The epoxy/BF_3-MEA and epoxy/PC/BF_3-MEA systems all follow the first order reaction. The PC modified systems show lower activation energy, a lower pre-exponential factor and a higher reaction rate constant.

  • The reactivity of epoxy/polyCarbonate/BF_3-MEA system
    Journal of Polymer Research, 2001
    Co-Authors: Ye-shiu Li, Feng-chih Chang
    Abstract:

    The cationic reaction of an epoxy/BF_3-MEA system occurs between the oxirane Group and the oxonium Group. The addition of polyCarbonate to the system does not cause a transesterification reaction between the Carbonate Group and the oxonium Group, thus the molecular weight of the PC is unchanged during the reaction. PC crystallization is observed in the cured system because the epoxy monomer accelerates the PC crystallization. The epoxy/BF_3-MEA and epoxy/PC/BF_3-MEA systems all follow the first order reaction. The PC modified systems show lower activation energy, a lower pre-exponential factor and a higher reaction rate constant.

  • Mechanism of transesterification and cyclization of epoxy–polyCarbonate blends catalyzed by quarternary ammonium salt
    Journal of Polymer Science Part A: Polymer Chemistry, 1996
    Co-Authors: Chen-chi M., Miaw-ling Lin, Feng-chih Chang
    Abstract:

    The reaction of oxirane with Carbonate using quarternary ammonium salts as catalyst has been studied. Curing is caused by the transesterification reaction of the oxirane cycle with the Carbonate Group that proceeds by an “insertion” mechanism in the stoichiometric system. The ratio of the reactants is two oxirane Groups to one Carbonate Group. In the nonstoichiometric system, the epoxide content is more than the stoichiometric quantity required. A cyclization reaction is followed by the transesterification reaction. To identify the finished products, a model reaction was proposed using diphenyl Carbonate and phenyl glycidyl ether which results in the formation of 4-phenoxymethyl-1,3-dioxolane-2-one (PMD). The mechanism of forming the cyclic structure is assumed to proceed through the chain scission of the network in which the molecular chain crosslinked with Carbonate Group by a transesterification reaction. © 1996 John Wiley & Sons, Inc.

  • Epoxy−PolyCarbonate Blends Catalyzed by a Tertiary Amine. 1. Mechanism of Transesterification and Cyclization
    Macromolecules, 1996
    Co-Authors: Chen-chi M., Miaw-ling Lin, Jyh-luen Chen, Feng-chih Chang
    Abstract:

    In the Bisphenol A base polyCarbonate−Bisphenol A base epoxy blend system, the Carbonate Group can react with epoxide in the presence of a tertiary amine. The transesterification reactions convert the original aromatic/aromatic Carbonate of PC to aromatic/aliphatic and aliphatic/aliphatic Carbonates. IR spectroscopy shows an unknown major structure formed during the later stages of the transesterification reaction. The unknown structure was investigated by a model reaction using diphenyl Carbonate and phenyl glycidyl ether leading to the formation of 4-(phenoxymethyl)-1,3-dioxolan-2-one (PMD), which has been identified by IR, UV, 1H NMR, 13C NMR, and mass spectroscopy. The mechanism of forming the cyclic Carbonate is proposed to proceed through a zwitterion and a nucleophile attack of the aromatic/aliphatic or the aliphatic/aliphatic Carbonate Group.

  • Transesterification and cyclization of polyCarbonate-epoxy blends cured with anhydride
    Polymer, 1996
    Co-Authors: Chen-chi M., Jyh-luen Chen, Feng-chih Chang
    Abstract:

    Abstract Infrared spectra have been investigated to study the curing mechanisms of polyCarbonate-epoxy blends using anhydride as a hardener catalysed by tertiary amine. Due to a significant difference in the reaction, curing reactions of the system can be considered as two sequential stages: (1) an anionic alternating copolymerization of cyclic anhydride and epoxy resin, and (2) a homopolymerization of oxirane initiated by a quaternary ammonium salt zwitter ion. The transesterification/cyclization of Carbonate Groups proceeds in the later stage if the oxirane is still available. Degrees of transesterification/cyclization and homopolymerization are higher when a higher epoxy/anhydride ratio is used. This study positively confirms the mechanism of transesterification/cyclization proceeding through a zwitter ion. The zwitter ion is formed from epoxide and tertiary amine, which attacks the Carbonate Group.

Rolf Mülhaupt - One of the best experts on this subject based on the ideXlab platform.

  • Polyfunctional Acrylic Non-isocyanate Hydroxyurethanes as Photocurable Thermosets for 3D Printing
    Macromolecules, 2019
    Co-Authors: Vitalij Schimpf, Anne Asmacher, Andre Fuchs, Bernd Bruchmann, Rolf Mülhaupt
    Abstract:

    Liquid acrylic oligourethanes are components of photocurable thermoset resins for applications ranging from coatings to 3D printing technologies like stereolithography. Traditionally they are derived from isocyanates which are highly moisture sensitive and do not tolerate hydroxy Groups. Herein we report on a versatile non-isocyanate route toward tailoring hydroxyurethane methacrylates (HUMA) and their oligomers for photo cross-linking and 3D printing. The key intermediate is (2-oxo-1,3-dioxolan-4-yl)methyl methacrylate, also referred to as methacrylated glycerol Carbonate, obtained by the chemical fixation of carbon dioxide with glycidyl methacrylate. Upon aminolysis with di- and polyfunctional aliphatic amines, the ring-opening reaction of the cyclic Carbonate Group yields HUMA. No handling of isocyanates is required. The HUMA molecular architectures govern photo cure as well as thermal and mechanical properties. An alternative strategy toward molecular design of polyfunctional acrylics exploits chemica...

  • isocyanate free route to poly carbohydrate urethane thermosets and 100 bio based coatings derived from glycerol feedstock
    Macromolecules, 2016
    Co-Authors: Stanislaus Schmidt, Bernd Bruchmann, Benjamin S Ritter, Daniel Kratzert, Rolf Mülhaupt
    Abstract:

    Glycerol serves as the exclusive bio feedstock for the preparation of high purity sorbitol triCarbonate (STC) as new intermediate for poly(carbohydrate–urethane) thermosets and 100% bio-based non-isocyanate polyhydroxyurethane (NIPU) coatings. In this process, glycerol-based acrolein is dimerized, Carbonated, and oxidized, thus producing the highly reactive diepoxy functional ethylene Carbonate (DOC), which by facile chemical CO2 fixation yields high purity STC. Opposite to most state-of-the-art multifunctional five-membered cyclic Carbonates and regardless of the feedstock used for its manufacture, STC enables amine curing at ambient temperature even in the absence of catalysts. According to FT-IR and NMR spectroscopic analyses of the amine/Carbonate reaction kinetics, the internal cyclic Carbonate Group is 3 times more reactive with respect to the two terminal Carbonate Groups. This is attributed to the electron-withdrawing effect of terminal cyclic Carbonates. Curing STC with a blend of bio-based flexi...

J Huter - One of the best experts on this subject based on the ideXlab platform.

  • studies on the influence of calcium formate on growth digestibility of crude nutrients nitrogen balance and calcium retention in weaned piglets
    Animal Feed Science and Technology, 1993
    Co-Authors: J Pallauf, J Huter
    Abstract:

    Abstract An experiment with 3 × 12 weaned piglets was carried out to study the nutritive efficacy of 1.5% dietary calcium formate (Group C) in comparison to calcium Carbonate (Group A) and calcium formate in addition to calcium Carbonate (Group B). The criteria studied were growth, feed conversion efficiency and, in two balance trials starting at live weights of 10 kg and 20 kg. digestibility of nutrients as well as retention of nitrogen and calcium. Calcium formate as an energy-providing mineral compound lowered the pH value of the diet from 6.5 to 5.6 and stabilized the digestion of the piglets with fewer incidences of diarrhoea. With calcium formate instead of calcium Carbonate, daily gain was 3.2% higher and the feed conversion efficiency was improved by 3.7%. From 10 kg to 20 kg body weight, the digestibility of nutrients increased in all Groups. Calcium formate improved the digestibility of organic matter, crude ash, crude fibre and nitrogen-free extractives (NfE) significantly, at least in one balance trial. No differences were observed in nitrogen-retention, whereas the digestibility of calcium and calcium-retention as a percentage of intake were significantly improved by calcium formate in both balance trials. Calcium formate as a supplement to a diet already meeting calcium requirements had a negative effect with regard to feed intake, daily gain and feed conversion efficiency. In particular the digestibility of fat was significantly reduced. For this reason total calcium should not exceed the optimum level when calcium formate is supplemented to piglet diets.

Michael C. Beuhler - One of the best experts on this subject based on the ideXlab platform.

  • Calcium Carbonate for Elemental Lead Ingestions: Effect of Alkalinization on Elemental Lead Solubility in a Simulated Gastric Environment
    Journal of Medical Toxicology, 2020
    Co-Authors: Kartik R. Shah, Michael S. Runyon, Michael C. Beuhler
    Abstract:

    Introduction Acute ingestion of elemental lead foreign bodies has resulted in multiple pediatric deaths. Elemental lead is relatively insoluble at alkaline pH. Furthermore, calcium decreases lead absorption by interfering with the lead absorptive receptor. We hypothesize that alkalinization of gastric fluid with an oral calcium-containing agent, such as calcium Carbonate, will decrease lead solubility, thus reducing the potential for systemic lead absorption and toxicity. Methods This was an in vitro controlled study. One lead sphere (00 buckshot, cast 30 days prior) was randomly placed in each of ten tubes containing 20 mL simulated gastric fluid, with five tubes having 500 mg calcium Carbonate added at 20 min and 140 min. We measured the fluid pH and the lead concentrations hourly for 4 h. We compared the median amount of total lead liberated after 4 h between the two Groups using the Mann-Whitney U test. Results The pH of the gastric fluid only tubes remained 1 at every measurement, and the pH of the gastric fluid + calcium Carbonate tubes was 6 at every measurement. At hour 4, the total amount of lead liberated in the soluble fraction in the control Group vs the calcium Carbonate Group was 850 vs 12.4 mcg (95% CI for absolute difference: 605–964 mcg; p = 0.0079). Conclusions Calcium Carbonate antacid alkalinizes gastric fluid pH and dramatically decreases the total amount of solubilized lead by 60-fold. This project lends foundational evidence to a low-cost, widely available, pre-hospital strategy to decrease lead absorption after acute elemental lead ingestions.