It is Better with Salt: Aqueous Ring-Opening Metathesis Polymerization at Neutral pH

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It is Better with Salt : Aqueous Ring-Opening Metathesis Polymerization at Neutral pH. / Foster, Jeffrey C; Grocott, Marcus C; Arkinstall, Lucy A; Varlas, Spyridon; Redding, McKenna J; Grayson, Scott M; O'Reilly, Rachel K.

In: Journal of the American Chemical Society, Vol. 142, No. 32, 12.08.2020, p. 13878-13885.

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Foster, Jeffrey C ; Grocott, Marcus C ; Arkinstall, Lucy A ; Varlas, Spyridon ; Redding, McKenna J ; Grayson, Scott M ; O'Reilly, Rachel K. / It is Better with Salt : Aqueous Ring-Opening Metathesis Polymerization at Neutral pH. In: Journal of the American Chemical Society. 2020 ; Vol. 142, No. 32. pp. 13878-13885.

Bibtex

@article{ee333b34370f474ba32b68148444a4f6,
title = "It is Better with Salt: Aqueous Ring-Opening Metathesis Polymerization at Neutral pH",
abstract = "Aqueous ring-opening metathesis polymerization (ROMP) is a powerful tool for polymer synthesis under environmentally friendly conditions, functionalization of biomacromolecules, and preparation of polymeric nanoparticles via ROMP-induced self-assembly (ROMPISA). Although new water-soluble Ru-based metathesis catalysts have been developed and evaluated for their efficiency in mediating cross metathesis (CM) and ring-closing metathesis (RCM) reactions, little is known with regards to their catalytic activity and stability during aqueous ROMP. Here, we investigate the influence of solution pH, the presence of salt additives, and catalyst loading on ROMP monomer conversion and catalyst lifetime. We find that ROMP in aqueous media is particularly sensitive to chloride ion concentration and propose that this sensitivity originates from chloride ligand displacement by hydroxide or H2O at the Ru center, which reversibly generates an unstable and metathesis inactive complex. The formation of this Ru-(OH)n complex not only reduces monomer conversion and catalyst lifetime but also influences polymer microstructure. However, we find that the addition of chloride salts dramatically improves ROMP conversion and control. By carrying out aqueous ROMP in the presence of various chloride sources such as NaCl, KCl, or tetrabutylammonium chloride, we show that diblock copolymers can be readily synthesized via ROMPISA in solutions with high concentrations of neutral H2O (i.e., 90 v/v%) and relatively low concentrations of catalyst (i.e., 1 mol %). The capability to conduct aqueous ROMP at neutral pH is anticipated to enable new research avenues, particularly for applications in biological media, where the unique characteristics of ROMP provide distinct advantages over other polymerization strategies.",
keywords = "ring-opening metathesis polymerization, cross metathesis, Ru-based metathesis catalysts, monomer conversion, catalyst lifetime",
author = "Foster, {Jeffrey C} and Grocott, {Marcus C} and Arkinstall, {Lucy A} and Spyridon Varlas and Redding, {McKenna J} and Grayson, {Scott M} and O'Reilly, {Rachel K}",
year = "2020",
month = aug,
day = "12",
doi = "10.1021/jacs.0c05499",
language = "English",
volume = "142",
pages = "13878--13885",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",
number = "32",

}

RIS

TY - JOUR

T1 - It is Better with Salt

T2 - Aqueous Ring-Opening Metathesis Polymerization at Neutral pH

AU - Foster, Jeffrey C

AU - Grocott, Marcus C

AU - Arkinstall, Lucy A

AU - Varlas, Spyridon

AU - Redding, McKenna J

AU - Grayson, Scott M

AU - O'Reilly, Rachel K

PY - 2020/8/12

Y1 - 2020/8/12

N2 - Aqueous ring-opening metathesis polymerization (ROMP) is a powerful tool for polymer synthesis under environmentally friendly conditions, functionalization of biomacromolecules, and preparation of polymeric nanoparticles via ROMP-induced self-assembly (ROMPISA). Although new water-soluble Ru-based metathesis catalysts have been developed and evaluated for their efficiency in mediating cross metathesis (CM) and ring-closing metathesis (RCM) reactions, little is known with regards to their catalytic activity and stability during aqueous ROMP. Here, we investigate the influence of solution pH, the presence of salt additives, and catalyst loading on ROMP monomer conversion and catalyst lifetime. We find that ROMP in aqueous media is particularly sensitive to chloride ion concentration and propose that this sensitivity originates from chloride ligand displacement by hydroxide or H2O at the Ru center, which reversibly generates an unstable and metathesis inactive complex. The formation of this Ru-(OH)n complex not only reduces monomer conversion and catalyst lifetime but also influences polymer microstructure. However, we find that the addition of chloride salts dramatically improves ROMP conversion and control. By carrying out aqueous ROMP in the presence of various chloride sources such as NaCl, KCl, or tetrabutylammonium chloride, we show that diblock copolymers can be readily synthesized via ROMPISA in solutions with high concentrations of neutral H2O (i.e., 90 v/v%) and relatively low concentrations of catalyst (i.e., 1 mol %). The capability to conduct aqueous ROMP at neutral pH is anticipated to enable new research avenues, particularly for applications in biological media, where the unique characteristics of ROMP provide distinct advantages over other polymerization strategies.

AB - Aqueous ring-opening metathesis polymerization (ROMP) is a powerful tool for polymer synthesis under environmentally friendly conditions, functionalization of biomacromolecules, and preparation of polymeric nanoparticles via ROMP-induced self-assembly (ROMPISA). Although new water-soluble Ru-based metathesis catalysts have been developed and evaluated for their efficiency in mediating cross metathesis (CM) and ring-closing metathesis (RCM) reactions, little is known with regards to their catalytic activity and stability during aqueous ROMP. Here, we investigate the influence of solution pH, the presence of salt additives, and catalyst loading on ROMP monomer conversion and catalyst lifetime. We find that ROMP in aqueous media is particularly sensitive to chloride ion concentration and propose that this sensitivity originates from chloride ligand displacement by hydroxide or H2O at the Ru center, which reversibly generates an unstable and metathesis inactive complex. The formation of this Ru-(OH)n complex not only reduces monomer conversion and catalyst lifetime but also influences polymer microstructure. However, we find that the addition of chloride salts dramatically improves ROMP conversion and control. By carrying out aqueous ROMP in the presence of various chloride sources such as NaCl, KCl, or tetrabutylammonium chloride, we show that diblock copolymers can be readily synthesized via ROMPISA in solutions with high concentrations of neutral H2O (i.e., 90 v/v%) and relatively low concentrations of catalyst (i.e., 1 mol %). The capability to conduct aqueous ROMP at neutral pH is anticipated to enable new research avenues, particularly for applications in biological media, where the unique characteristics of ROMP provide distinct advantages over other polymerization strategies.

KW - ring-opening metathesis polymerization

KW - cross metathesis

KW - Ru-based metathesis catalysts

KW - monomer conversion

KW - catalyst lifetime

UR - http://www.scopus.com/inward/record.url?scp=85089609411&partnerID=8YFLogxK

U2 - 10.1021/jacs.0c05499

DO - 10.1021/jacs.0c05499

M3 - Article

C2 - 32673484

VL - 142

SP - 13878

EP - 13885

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

SN - 0002-7863

IS - 32

ER -