Browsing by Author "Kellstedt, Elizabeth A"

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    Supporting Data for Tandem ROMP/Hydrogenation Approach to Hydroxy-Telechelic Linear Polyethylene
    (2022-04-11) Sample, Caitlin S; Kellstedt, Elizabeth A; Hillmyer, Marc A; hillmyer@umn.edu; Hillmyer, Marc A; Hillmyer Group
    These files contain data along with associated output from instrumentation supporting all results reported in Sample et. al. "Tandem ROMP/Hydrogenation Approach to Hydroxy-Telechelic Linear Polyethylene." In Sample et. al. we found: Hydroxy-telechelic polycycloalkenamers have long been synthesized using ring-opening metathesis polymerization (ROMP) in the presence of an acyclic olefin chain-transfer agent (CTA); however, this route typically requires protected diols in the CTA due to the challenge of alcohol-mediated degradation of ruthenium metathesis catalysts that can not only deactivate the catalysts but also compromise the CTA. We demonstrate the synthesis and implementation of a new hydroxyl-containing CTA in which extended methylene spacers isolate the olefin and alcohol moieties to mitigate decomposition pathways. This CTA enabled the direct ROMP synthesis of hydroxy-telechelic polycyclooctene with controlled chain lengths dictated by the initial ratio of monomer to CTA. The elimination of protection/deprotection steps resulted in improved atom economy. Subsequent hydrogenation of the backbone olefins was performed by a one-pot, catalytic approach employing the same ruthenium alkylidene catalyst used for the initial ROMP. The resultant approach is a stream-lined, atom-economic, and low-waste route to hydroxy-telechelic linear polyethylene that uses a green solvent, succeeds with miniscule quantities of catalyst (0.005 mol%), and requires no additional purification steps.
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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.