Browsing by Author "Xu, Shu"

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    Renewable Monomers and Polymers from Biomass-derived Acids and Furans
    (2021-02) Xu, Shu
    Biomass-derived acids and furans are great building blocks of renewable plastics. This thesis focuses on the synthesis of novel biomass-based reactive monomers and polymers as well as the study of degradation of polymeric materials. Chapter 2 covers the synthesis of a reactive lactone monomer from levulinic acid. Polymerization of this lactone produced a semicrystalline polyketoester with high melting temperatures. The hydrolytic degradation of this polyketoester was also studied. Under aqueous basic conditions or Brønsted acidic conditions, different degradation products were observed. Chapter 3 details the Diels-Alder reaction between furans and itaconic anhydride. The highly efficient Diels-Alder reaction between furfuryl alcohol and itaconic anhydride into a single diastereomeric adduct. This adduct was demonstrated to be a good building block for production of several aromatic compounds that are potentially reactive monomers and a metathesis polymer. Chapter 4 describes the production of alpha-methyleneglutarimides as reactive monomers for radical polymerizations. The synthesis of this monomer started from an itaconic acid derivative. We reported the thermal properties of these polymers as well as the attempt to depolymerization through mere heat. Chapter 5 is about an ongoing project targeting dimethylnaphthalenes from biomass. Poly(ethylene naphthalate) (PEN) is a poly(ethylene terephthalate) (PET) substitute with better mechanical properties, and dimethylnaphthalene is a precursor for producing PEN. Our attempt towards the synthesis of dimethylnaphthalene from biomass-derived feedstock is discussed in this chapter.
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    Supporting data for Primary data for Poly(4-ketovalerolactone) from Levulinic acid, Synthesis and Hydrolytic Degradation
    (2020-06-10) Xu, Shu; Wang, Yuanxian; Hoye, Thomas R; hoye@umn.edu; Hoye, Thomas R
    These files contain primary data along with associated output from instrumentation supporting all results reported in Xu et. al. Primary data for Poly(4-ketovalerolactone) from Levulinic acid, Synthesis and Hydrolytic Degradation. In Xu et al. we found: We report here the synthesis of poly(4-ketovalerolactone) (PKVL) via ring-opening transesterification polymerization (ROTEP) of the monomer 4-ketovalerolactone (KVL, two steps from levulinic acid). The polymerization of KVL proceeds to high equilibrium monomer conversion (up to 96% in the melt) to give the semicrystalline polyketoester PKVL with low dispersity. PKVL displays glass transition temperatures of 7 °C and two melting temperatures at 132 and 148 °C. This polyester can be chemically recycled through hydrolytic degradation. Under aqueous neutral or acidic conditions, the dominating pathway for polyester hydrolysis is through backbiting from the chain end. Under basic conditions, mid-chain cleavage, accelerated by the ketone carbonyl group in the backbone, promotes the hydrolysis of nearby backbone ester bonds. The final hydrolysis product is 5-hydroxylevulinic acid, the ring opened hydrolysis product of KVL. PKVL was also observed to degrade under the action of a Brønsted acid to a bis-spirocyclic dilactone natural product altaicadispirolactone, which is a dimer of KVL. This constitutes a rare example of a one-step synthesis of a secondary metabolite in which a polymer was the starting material and the sole source of matter. Analogous ROTEP of the isomeric 4-membered lactone 4-acetyl--propiolactone (APL) was also explored, although this chemistry was not as well-behaved as the KVL to PKVL polymerization.