Browsing by Author "Watts, Annabelle"
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Item Entropically-driven macrolide polymerizations for the synthesis of aliphatic polyester copolymers using titanium isopropoxide(2019-03-11) Amador, Adrian G; Watts, Annabelle; Neitzel, Angelika, E; Hillmyer, Marc A; hillmyer@umn.edu; Hillmyer, Marc A; Hillmyer research group UMN ChemistryThermal and mechanical properties of sustainable aliphatic polyesters can be tuned through the synthesis of copolymers. The synthesis of two 14-membered macrolides are reported: a cyclic tetraester with alternating lactic acid (LA) and 3-hydroxypropionic acid (3HP) units and a cyclic diester with alternating glycolic acid (GA) and 2-methyl-1,3-propanediol (2MD) units. Ring-opening transesterification polymerization (ROTEP) of these macrolides to yield poly(LA-stat-3HP) and poly(GA-alt-2MD), respectively, were found to be modestly endothermic (ΔHp° = 2.0 kJ mol-1 and 0.5 kJ mol-1, respectively) and endoentropic (ΔSp° = 27 J mol-1 K-1 and 23 J mol-1 K-1, respectively). Inexpensive and non-toxic titanium isopropoxide Ti(Oi-Pr)4 functions as an active catalyst for these entropically-driven ROTEPs, achieving high conversions (> 90%) in under 1 h. The polymerizations exhibit control over molar mass with dispersity values < 1.7. P(GA-alt-2MD) is an amorphous polymer with a low glass transition temperature near −30 °C. P(LA-co-3HP) exhibits a glass transition temperature up to 13 °C and depending on the regioregularity, exhibits a melting temperature up to 96 °C.Item High performing sustainable thermoplastic elastomers(2019-01) Watts, AnnabelleThermoplastic elastomers (TPEs) exhibit a wide range of properties and are easy to process as they are made of physical, rather than chemical, crosslinks. Many factors contribute to the varied physical properties seen in elastomeric TPEs, defining whether the resultant material is a soft elastomer suitable for adhesives, or a hard elastomer with competitive properties to vulcanized natural rubber. The sustainable polymers studied in this work are able to be synthesized through commercially available reagents and through controlled polymerization methods. Through the design of sustainable block polymers, we have gained insight into properties such as polymer entanglement that govern TPE mechanical behavior. High molar mass systems demonstrate high strength and high extensibility, yielding tough elastomers. Incorporating crystallinity or hydrogen-bonding groups results in improved mechanical properties and reduced stress relaxation. This work presents the synthesis of sustainable polymers and the investigation into the fundamental polymer properties essential to designing high performing TPEs.Item Supporting data for "Efficient Polymerization of Methyl-ε-Caprolactone Mixtures to Access Sustainable Aliphatic Polyesters"(2020-02-26) Batiste, Derek, C; Meyersohn, Marianne S; Hillmyer, Marc A; Watts, Annabelle; hillmyer@umn.edu; Hillmyer, Marc A; University of Minnesota, Hillmyer Lab, Department of ChemistryThese files contain primary data along with associated output from instrumentation supporting all results reported in Batiste et. al. "Efficient Polymerization of Methyl-ε-Caprolactone Mixtures to Access Sustainable Aliphatic Polyesters." In Batiste et. al. we found: Aliphatic polyesters are a versatile class of materials that can be sourced from bioderived feedstocks. Poly(γ-methyl-ε-caprolactone) (PγMCL) in particular can be used to make degradable thermoplastic elastomers (TPEs) with outstanding mechanical properties. PγMCL can potentially be manufactured economically from p-cresol, a component of lignin bio oils. A complication is that additional manufacturing processes are necessary to isolate pure cresol isomers. Using mixed feedstocks of cresol isomers to access the corresponding methyl substituted ε-caprolactone (MCL) monomer mixtures would convey economic advantages to sourcing these materials sustainably. Moreover, the use of organocatalysts in lieu of traditional tin-based catalysts averts issues with potential environmental and human toxicity. With these motivations in mind, we explored the ring-opening transesterification polymerization (ROTEP) of MCL mixtures and characterized the molecular, thermal and rheological properties of the resulting copolymers. The molar mass of MCL mixtures that would be obtained from meta- and para-cresol can be readily modulated. The thermal and rheological properties of these statistical co- and terpolymers were at parity with pure PγMCL homopolymer. The use of diphenyl phosphate (DPP) and dimethyl phosphate (DMP) as organocatalysts enabled access to these materials on reasonable polymerization timescales and have potential to improve sustainability in the synthesis of these polyesters.