Browsing by Subject "Polyesters"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Application of deep eutectic solvents and ionic liquids to hydrolase-catalyzed reactions.
    (2010-01) Gorke, Johnathan Thomas
    Hydrolases are important enzymes for stereoselective and environmentally benign synthesis. In nature, hydrolases cleave bonds with water. When used in organic solvents, these enzymes can make synthetically useful bonds through condensation and the release of a small molecule, usually water or an alcohol. Many organic solvents that preserve enzyme activity, such as toluene, can be environmentally damaging or toxic. Room temperature ionic liquids, poorly coordinating salts that are liquid at temperatures below 100 degrees C, are a potential alternative to organic solvents for hydrolase-catalyzed reactions because of their low volatility, moderate polarity, and recyclability. However, many commonly used ionic liquids are orders of magnitude more expensive than conventional organic solvents and may also cause adverse environmental effects if released into aquatic environments. We demonstrate that ionic liquids are effective solvents for the lipase-catalyzed polymerization of epsilon-caprolactone and other poly(hydroxyalkanoates) and are effective in enhancing the electrical conductivity of carotenoid-containing polymers produced enzymatically. However, we found that they were not as effective as toluene for enzyme catalysis, and strove to find better alternative solvents for biotransformations. We discovered that deep eutectic solvents, mixtures of ammonium or metal salts such as choline chloride and hydrogen bond donors such as urea or glycerol, were exceptional low-cost, biodegradable alternatives to organic solvents for hydrolase-catalyzed reactions. These physical mixtures may be thought of as ionic liquids, because they share similar physical properties to those solvents. Though they are composed of potential denaturants such as urea or halide anions, deep eutectic solvents stabilize enzymes. This stabilization is likely due to a preference for intra-solvent hydrogen bonding compared to enzyme-solvent hydrogen bonding. Deep eutectic solvents enhanced enzyme activity for a number of lipases either as pure solvents for reactions such as transesterification or polyesterification; or as additives in aqueous reactions such as epoxide ring opening or ester hydrolysis. We have preliminary evidence that deep eutectic solvents may induce a conformational change in enzymes that can alter reaction rates. These changes appear to be distinct from those caused by denaturing.
  • Thumbnail Image
    Item
    Step-Growth Polyesters with Biobased (R)-1,3-Butanediol
    (2020-08-26) DeRosa, Christopher A; Kua, Xiang Qi; Bates, Frank S; Hillmyer, Marc A; hillmyer@umn.edu; Hillmyer, Marc A; University of Minnesota, Department of Chemistry
    These files contain primary data along with associated output from "Step-Growth Polyesters with Biobased (R)-1,3-Butanediol" by Hillmyer et al. We present the synthesis and characterization of polymers containing 1,3-butanediol, also known as butylene glycol. Butylene glycol (BG) can be prepared from petroleum or sugar-based feedstocks. Petrol-based BG (petrol-BG) is isolated as a racemic mixture, whereas the bio-based BG from sugar that we utilized (Bio-BG), is enantiopure upon purification (>99.7%). In the presence of a titanium catalyst, polyesters were prepared by transesterification polymerization between petrol- or Bio-BG and various aliphatic and aromatic diacid derivatives. Polymers were analyzed by size-exclusion chromatography (SEC), 1H NMR and 13C NMR spectroscopies, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The synthesized polyesters were statistical in nature, according to 13C NMR spectroscopy, a result of the asymmetric nature of the BG-starting material. As a result, many of the polyesters were amorphous in nature with low thermal glass transitions (Tg) and no melting points (Tm). In many of the polyester derivatives, the racemic petrol-based and enantiopure bio-based BG polymers were nearly identical in thermal performance. Differences arose in semi-crystalline polyesters with long, aliphatic backbones (e.g., 1,14-tetradecanediocic acid; C14 diacid) or regioregular 4-hydroxybenzoate polyesters. This suggests the polymer microstructure (statistical versus sequenced) and the optical activity (racemic versus enantiopure) are important determinates in establishing the structure-property relationships in BG-containing polyesters. This work establishes synthetic protocols and the foundation for materials based on BG-containing polymers.