Browsing by Author "Elser, Iris"

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Open Access
Dual catalysis with an N‐heterocyclic carbene and a Lewis acid : thermally latent precatalyst for the polymerization of ε‐caprolactam
(2020) Altmann, Hagen J.; Steinmann, Mark; Elser, Iris; Benedikter, Mathis J.; Naumann, Stefan; Buchmeiser, Michael R.
So far, the earlier reported strong correlation between basicity of an N‐heterocyclic carbene (NHC) and its reactivity in poly(ε‐caprolactam) (PA6) synthesis resulted in a substantial limitation of applicable carbenes. Here, to overcome this issue, 1,3‐dimethylimidazolium‐2‐carboxylate, an easily accessible, air and moisture‐stable NHC, was applied as thermally latent initiator. In order to compensate for its low basicity, reactivity was enhanced by the addition of both a Lewis acid and an activator to ease the initial polymerization step. The resulting mixtures of ε‐caprolactam, the CO2‐protected NHC, a Lewis acid and N‐acylazepan‐2‐one constitute homogeneous, thermally fully latent “single‐component” blends for the anionic polymerization‐based synthesis of PA6. They can be stored both in the liquid and solid state for days and months, respectively, without any loss in activity. The role of the Lewis acid as well as technical implications of the prolonged pot‐times are discussed.
Open Access
(Pre-)ionic and/or chiral alkene and alkyne metathesis catalysts of group 6
(2018) Elser, Iris; Buchmeiser, Michael R. (Prof. Dr.)
Ziel dieser Arbeit war es, zu der bereits bestehenden Katalysatorbibliothek für die Olefin- und Alkinmetathese beizutragen. So sollten neue Anwendungen ermöglicht werden und einige Herausforderungen wie Katalysatorstabilität, Katalysatorrückgewinnung und Stereoselektivität adressiert werden. Bei den beschriebenen Katalysatoren handelt es sich um Molybdän und Wolfram Alkyliden und Alkylidin Komplexe, welche durch N-heterozyklische Carbene (NHC) stabilisiert werden. Es konnten erfolgreich ionische Katalysatoren für die Biphasenkatalyse, Komplexe mit bidentaten NHC-Liganden sowie luftstabile und latente Katalysatoren für die industriell relevante ring-öffnende Metathesepolymerisation von Dizyklopentadien hergestellt werden. Zudem wurde eine Syntheseroute für Molybdän Imido Alkyliden NHC Komplexe mit sterisch anspruchsvollen und basischen Alkoxidliganden entwickelt. Auch wurden mechanistische Studien zur Aufklärung der aktiven Spezies von Molybdän Alkylidin NHC Komplexen in der Homometathese von 1-Phenyl-1-propin angefertigt.
Open Access
Silica‐supported cationic tungsten imido alkylidene stabilized by an N‐heterocyclic carbene ligand boosts activity and selectivity in the metathesis of α‐olefins
(2020) De Jesus Silva, Jordan; Mance, Deni; Pucino, Margherita; Benedikter, Mathis J.; Elser, Iris; Buchmeiser, Michael R.; Copéret, Christophe
A well‐defined silica‐supported cationic W imido alkylidene was prepared through surface organometallic chemistry. This catalyst shows preferential activity towards α‐ over internal olefins, which is atypical for W‐based catalysts, but consistent with the strong σ‐donating ability of the NHC ancillary ligand. Complementing the studies on tungsten‐based d0 metathesis catalysts, the silica‐supported cationic W imido alkylidene displays the highest activity among W imido catalysts for α‐olefins and shows improved selectivity for this class of olefins compared to Mo‐based catalysts.
Open Access
Toward sustainable fiber‐reinforced polymer composites
(2024) Elser, Iris; Buchmeiser, Michael R.
Fiber‐reinforced polymer composites (FRPCs) are versatile materials with applications in diverse fields such as transportation, construction, and electronics. With the composites market expected to reach 15.5 Mt by 2026, increasing the sustainability of FRPCs is imperative. The main factors driving the sustainability of FRPCs, namely end‐of‐life management and recyclability, the use of natural, bio‐based, and sustainable materials, as well as biodegradability and product simplification are presented and discussed.