A Ring‐Opening Metathesis Polymerization Catalyst That Exhibits Redox‐Switchable Monomer Selectivities

Lastovickova, Dominika N.; Shao, Huiling; Lü, Gang; Liu, Peng; Bielawski, Christopher W.

doi:10.1002/chem.201605738

Cited by 30 publications

(21 citation statements)

References 57 publications

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“…Inherent to switchable catalysts is the temporal control needed for programmable polymer sequences. Various external stimuli have been used in switchable polymerization reactions, but particularly effective has been redox-switchable catalysts . Since their original discovery for lactide polymerization, significant effort has been dedicated to controlling ring-opening polymerization processes by varying the oxidation states of metal catalysts …”

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confidence: 99%

Electrochemically Switchable Ring-Opening Polymerization of Lactide and Cyclohexene Oxide

et al. 2018

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An electrochemical method was developed for the redox switchable polymerization of lactide and cyclohexene oxide. Using a lithium reversible sacrificial electrode and a high surface area carbon working electrode, efficient transformation between formally iron(II) and iron(III) oxidation states of a bis(imino)pyridine iron alkoxide complex was possible, which led to the ability to activate the complex for ring opening polymerization reactions. In addition to serving as a redox trigger, an electrochemical toggle switch was developed in which the chemoselectivity for lactide and epoxide polymerization was altered in situ. These findings led to the synthesis of poly(lactic acid- b-cyclohexene oxide) block copolymers in which the sequence of monomers incorporated is controlled by the electrical potential applied.

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confidence: 99%

Electrochemically Switchable Ring-Opening Polymerization of Lactide and Cyclohexene Oxide

et al. 2018

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“…Similar to the aforementioned RCM reactions, the difference in catalytic activity was attributed to the suppression of the retro-[2 + 2] cycloaddition step of the corresponding catalytic cycle. 69 To determine if the rate constant differential may be utilized to potentiostatically control the kinetics of ROMP reactions over time, a cell was charged with a dichloromethane mixture of monomer ( (Figure 4b), as determined by GC. After 20% of the monomer converted to polymer, a potential of −0.95 V was applied which effectively slowed the reaction: k 1,red = 6.10 × 10 −5 s −1 (k 1 /k 1,red = 5.3).…”

Section: Resultsmentioning

confidence: 99%

Potentiostatically Controlled Olefin Metathesis

2020

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A Ru(II) complex supported by an N-heterocyclic carbene annulated to a redox-active naphthoquinone (NQ) was interrogated using a range of potentiodynamic and potentiostatic electrochemical techniques. The complex exhibited two redox processes, one of which was attributed to the Ru(II)|Ru(III) couple (E 1/2 = +1.10 V vs a saturated calomel electrode) and the other to the NQ|NQ − couple (E 1/2 = −0.62 V). Using potentiostatic coulometry or bulk electrolysis, the application of a fixed negative potential (−0.95 V) to electrodes placed in a dichloromethane solution containing the complex resulted in a reduction reaction. The complex was quantitatively reduced within minutes, as determined by coulometry, and subsequently oxidized to its initial, neutral form through the application of a relatively positive potential (+0.34 V) over similar periods of time. The interconversion process was found to be reversible and used to modulate a series of ring-closing metathesis and ring-opening metathesis polymerization reactions. While relatively high activities were observed when the neutral form of the catalyst was employed, the reaction rates were attenuated upon in situ, potentiostatic reduction. Toggling between relatively negative or positive potentials enabled the aforementioned olefin metathesis reactions to be switched between fast and slow states.

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“…TD1 3 , TD2 4 , NB3 5 and NB4 6 were synthesized according to the literature and their spectroscopic data were reported in the same literature. Scheme S1.…”

Section: Experimental Procedures For Small Molecule Synthesismentioning

confidence: 99%

“…1 NB5: NB5 was prepared using a modified literature procedure. 6 To a stirred solution of NB5-a (494mg, 3 mmol) in DMF (20mL), sodium hydride (60wt% dispersion in mineral oil, 121mg, 3 mmol) was added slowly at 0°C and stirred for 20min. To a reaction mixture, G2 (1.63g, 2 mmol) was added and stirred for 4h at RT.…”

Section: Scheme S2 Synthesis Of Nb2mentioning

confidence: 99%

Ru-Catalyzed, cis-Selective Living Ring-Opening Metathesis Polymerization of Various Monomers, Including a Dendronized Macromonomer, and Implications to Enhanced Shear Stability

et al. 2020

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An unsaturated polymer’s cis/trans-olefin content has a significant influence on its properties. For polymers obtained by ring-opening metathesis polymerization (ROMP), the cis/trans-olefin content can be tuned by using specific catalysts. However, cis-selective ROMP has suffered from narrow monomer scope and lack of control over the polymerization (giving polymers with broad molecular weight distributions and prohibiting the synthesis of block copolymers). Herein, we report the versatile cis-selective controlled living ROMP of various endo-tricyclo[4.2.2.02,5]deca-3,9-diene and various norbornene derivatives using a fast-initiating dithiolate-chelated Ru catalyst. Polymers with cis-olefin content as high as 99% could be obtained with high molecular weight (up to M n of 105.1 kDa) and narrow dispersity (<1.4). The living nature of the polymerization was also exploited to prepare block copolymers with high cis-olefin content for the first time. Furthermore, owing to the successful control over the stereochemistry and narrow dispersity, we could compare cis- and trans-rich polynorbornene and found the former to have enhanced resistance to shear degradation.

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A Ring‐Opening Metathesis Polymerization Catalyst That Exhibits Redox‐Switchable Monomer Selectivities

Cited by 30 publications

References 57 publications

Electrochemically Switchable Ring-Opening Polymerization of Lactide and Cyclohexene Oxide

Electrochemically Switchable Ring-Opening Polymerization of Lactide and Cyclohexene Oxide

Potentiostatically Controlled Olefin Metathesis

Ru-Catalyzed, cis-Selective Living Ring-Opening Metathesis Polymerization of Various Monomers, Including a Dendronized Macromonomer, and Implications to Enhanced Shear Stability

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