Browsing by Subject "ROMP"

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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 Regio- and stereoregular EVOH Copolymers from ROMP as Designer Barrier Materials
    (2024-04-03) Hillmyer, Marc A; Dingwell, Claire; hillmyer@umn.edu; Hillmyer, Marc A; Hillmyer Research Group
    This work aimed to decrease the water permeability (PH2O), while simultaneously maintaining low oxygen permeability (PO2) in ethylene vinyl alcohol (EVOH) based copolymers by introducing high levels of backbone regioregularity and stereoregularity. Both regioregular atactic and isotactic EVOH samples with 75 mol% ethylene were prepared by a ring-opening metathesis polymerization (ROMP)-hydrogenation-deprotection approach and then compared to commercial EVOH(44) (containing 44 mol% ethylene) as a low PO2 standard with poor water barrier characteristics (i.e., high PH2O). The high levels of regioregularity and stereoregularity in these copolymers increased melting temperature (Tm), degree of crystallinity (χc), and glass transition temperature (Tg) compared to less regular structures. EVOH(44) demonstrated the highest Tm, but lower χc and Tg values as compared to the ROMP-derived polymers. Wide-angle X-ray scattering showed that semi-crystalline EVOH(44) exhibited a monoclinic structure characteristic of commercial materials, while ROMP-derived polymers displayed an intermediate structure between monoclinic and orthorhombic. Tensile testing showed that isotacticity resulted in brittle mechanical behavior, while the atactic and commercial EVOH(44) samples had higher tensile toughness values. Although EVOH(44) had the lowest PO2 of the samples explored, the atactic and tough ROMP-derived polymer approached this value of PO2 while having a PH2O over 3 times lower than commercial EVOH(44).