Browsing by Author "Hoehn, Brenden D"

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    Supporting data for Crosslinked polyolefins through tandem ROMP/hydrogenation
    (2024-03-14) Hillmyer, Marc A; Sample, Caitlin S; Hoehn, Brenden D; hillmyer@umn.edu; Hillmyer, Marc A; Hillmyer Research Group
    These files contain primary data along with associated output from instrumentation supporting all results reported in Sample et al. "Crosslinked Polyolefins Through Tandem ROMP/Hydrogenation". Crosslinked polyolefins have important advantages over their thermoplastic analogues, particularly improved impact strength and abrasion resistance, as well as increased chemical and thermal stability; however, most strategies for their production involve post-polymerization crosslinking of polyolefin chains. Here, a tandem ring-opening metathesis polymerization (ROMP)/hydrogenation approach is presented. Cyclooctene (COE)-co-dicyclopentadiene (DCPD) networks are first synthesized using ROMP, after which the dispersed Ru metathesis catalyst is activated for hydrogenation through addition of hydrogen gas. The reaction temperature for hydrogenation must be sufficiently high to allow mobility within the system, as dictated by thermal transitions (i.e., glass and melting transitions) of the polymeric matrix. COE-rich materials exhibit branched-polyethylene-like crystallinity (25% crystallinity) and melting points (Tm = 107 °C), as well as excellent ductility (>750 % extension), while majority DCPD materials are glassy (Tg = 84 °C) and much stiffer (E = 710 MPa); all materials exhibit high tensile toughness. Importantly, hydrogenation of olefins in these crosslinked materials leads to notable improvements in oxidative stability, as saturated networks do not experience the same substantial degradation of mechanical performance as their unsaturated counterparts upon prolonged exposure to air at high temperature.
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    Supporting data for Tough Polycyclooctene Nanoporous Membranes from Etchable Block Copolymers
    (2023-12-14) Hoehn, Brenden D; Kellstedt, Elizabeth A; Hillmyer, Marc A; hillmyer@umn.edu; Hillmyer, Marc A; Hillmyer Research Group
    These files contain primary data along with associated output from instrumentation supporting all results reported in Hoehn et al. "Tough Polycyclooctene Nanoporous Membranes from Etchable Block Copolymers". In Hoehn et al. we found porous materials with pore dimensions of the nanometer length scale are useful as nanoporous membranes. ABA triblock copolymers are convenient precursors to such nanoporous materials if the end blocks are easily degradable (e.g., polylactide or PLA) in thin films leaving nanoporous polymeric membranes (NPMs). The membrane properties are dependent on midblock monomer structure, triblock copolymer composition, overall molar mass, and polymer processing conditions. Polycyclooctene (PCOE) NPMs were prepared using this method, with tunable pore sizes on the order of tens of nanometers. Solvent casting was shown to eliminate film defects and allowed achievement of superior mechanical properties over melt processing techniques, and PCOE NPMs were found to be very tough, a major advance over previously reported NPMs. Oxygen plasma etching was used to remove the surface skin layer to obtain membranes with higher surface porosity, membrane hydrophilicity, and flux of both air and water. This is a straightforward method to reliably produce highly tough NPMs with high levels of porosity and hydrophilic surface properties.