Ultra-High-Molecular-Weight Macrocyclic Bottlebrushes via Post-Polymerization Modification of a Cyclic Polymer

Pal, Digvijayee; Miao, Zhihui; Garrison, John B.; Veige, Adam S.; Sumerlin, Brent S.

doi:10.1021/acs.macromol.0c01797

Cited by 41 publications

(37 citation statements)

References 57 publications

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“…Providing evidence of a cyclic structure remains challenging due to the insoluble nature of PA. Atomic force microscopy (AFM) images of cyclic bottlebrush derivatives of c-PA provide absolute evidence for the cyclic topology. 34,48 Another approach to confirming the cyclic topology is to first synthesize a soluble precursor and execute solution-phase structural investigations prior to forming c-PA. Herein, we report the ring-expansion metathesis polymerization (REMP) of cyclic alkenes via tungsten alkylidyne catalyst 2 49,50 to yield soluble cyclic polymer precursors to c-PA. Accessible now from a soluble and processable polymer precursor are lustrous thin films of c-PA that exhibit high conductivity when doped.…”

Section: ■ Introductionmentioning

confidence: 99%

Soluble Polymer Precursors via Ring-Expansion Metathesis Polymerization for the Synthesis of Cyclic Polyacetylene

et al. 2021

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Cyclic polyacetylene (c-PA) is the cyclic derivative of the semiconducting linear polyacetylene. As with the linear derivative, cyclic polyacetylene is insoluble, making its characterization and processing challenging. Herein, we report the synthesis of c-PA via an indirect approach, employing ring-expansion metathesis polymerization of cyclic alkenes to form soluble polymer precursors. Subsequent retro-Diels−Alder elimination through heating provides c-PA. Dilute solution characterizations of the polymer precursors including 1 H nuclear magnetic resonance spectroscopy, gel permeation chromatography, and infrared and Raman spectroscopy confirm their cyclic structure and, by inference, the cyclic topology of the resulting c-PA. Solid-state thermal analyses via thermogravimetric analysis and differential scanning calorimetry reveal the chemical and physical transformations occurring during the retro-Diels−Alder elimination step and concurrent isomerization. Freestanding films are attainable via the soluble precursors, and when doped with I 2 , the films are semiconducting.

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Section: ■ Introductionmentioning

confidence: 99%

Soluble Polymer Precursors via Ring-Expansion Metathesis Polymerization for the Synthesis of Cyclic Polyacetylene

et al. 2021

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“…The important outcome of this investigation is that a catalyst capable of cyclic polymer synthesis − ,− is now accessible from commercially available starting materials in one step. In this iteration, the specific ene-ol proligand 2 was chosen to mimic fluorinated alkoxides prevalent in Mo- and W-metathesis catalysts .…”

Section: Discussionmentioning

confidence: 99%

Double Tethered Metallacyclobutane Catalyst for Cyclic Polymer Synthesis

et al. 2021

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This work outlines an approach to creating a catalyst for cyclic polymer synthesis using readily available materials in only one or two steps. Combining commercially available molybdenum-alkylidene 1 with two equivalents of ene-ol proligand 2 rapidly produces, in quantitative yield ( 1 H NMR spectroscopy), the double tethered metallacyclobutane complex 3. Characterized by variable temperature NMR studies and nuclear Overhauser effect spectroscopy (NOESY) experiments, complex 3 exhibits fluxional behavior in solution. Determined by single crystal X-ray diffraction, the solid-state structure of complex 3 reveals metrical parameters indicating that the metallacyclobutane is not predicted to undergo rapid retro-cycloaddition. However, complex 3 is a precatalyst for the polymerization of norbornene to produce cyclic polynorbornene. An NMR spectrum of a test polymerization indicates that only a small fraction of the precatalyst is activated upon exposure to monomer. Quantifying the active catalyst is possible by measuring vinyl resonances that appear in the 1 H NMR spectrum. The vinyl resonances are attributable to the release of one of the tethers upon norbornene addition. Confirmation of the polymer cyclic topology comes from gel permeation chromatography (GPC), dynamic light scattering (DLS), and intrinsic viscosity (η) measurements. The double tethered metallacyclobutane complex is a novel design for catalytic cyclic polymer synthesis. The synthetic approach suggests that catalyst tuning is possible by a choice of the commercial alkylidene and alteration of the ene-ol proligand.Article pubs.acs.org/JACS

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“…19 20 Similar to examples from Tew, 16 W2 can also be used in bottlebrush polymer applications via graft-from methodology. 21…”

Section: Ring-expansion Metathesis Polymerization (Remp) With Non-ruthenium Initiatorsmentioning

confidence: 99%

“…19,20 Similar to examples from Tew, 16 W2 can also be used in bottlebrush polymer applications via graft-from methodology. 21 Fischer also accessed cyclic conjugated polymers from alkyne monomers through orthogonal ring-opening alkyne metathesis polymerization (ROAMP); 22 this work resulted in the synthesis of highly-strained, carbon-rich conjugated polymers. The molybdenum initiator developed by Fischer differentiated between linear and cyclic poly(o-phenylene ethynylene) based on ligand sterics, ultimately providing access to divergent mechanistic pathways derived from metathesis chemistry (Scheme 3b).…”

Section: Synpacts Synlettmentioning

confidence: 99%

Ring-Expansion Metathesis Polymerization Initiator Design for the Synthesis of Cyclic Polymers

Golder¹,

Morrison²

2022

Synlett

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Cyclic polymers are of increasing interest to the synthetic and physical polymer communities due to their unique structures that lack chain ends. This topological distinction results in decreased chain entanglement, lower intrinsic viscosity, and smaller hydrodynamic radii. Many methods for the production of cyclic polymers exist, however, large-scale production of architecturally pure cyclic polymers is challenging. Ring-expansion metathesis polymerization (REMP) is an increasingly promising method to produce cyclic polymers because of the mild and scalable reaction conditions. Herein, a brief history of REMP for the synthesis of cyclic polymers with both ruthenium and non-ruthenium initiators is discussed. Even though REMP is a promising method for synthesizing cyclic polymers, state-of-the-art methods still struggle with poor molar mass control, slow polymerization rates, low conversion, and poor initiator stability. To combat these challenges, our group has developed a tethered ruthenium-benzylidene initiator, CB6, which utilizes design features from ubiquitous Grubbs-type initiators used in linear polymerizations. These structural modifications are shown to improve initiator kinetics, enhance initiator stability, and increase control over the molar mass of the resulting cyclic polymers.1 Introduction2 Ring-Expansion Metathesis Polymerization (REMP) with Ruthenium Initiators3 New Developments in Ruthenium Ring-Expansion Metathesis (REMP) Initiator Design4 Ring-Expansion Metathesis Polymerization (REMP) with Non-Ruthenium Initiators5 Conclusions

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Ultra-High-Molecular-Weight Macrocyclic Bottlebrushes via Post-Polymerization Modification of a Cyclic Polymer

Cited by 41 publications

References 57 publications

Soluble Polymer Precursors via Ring-Expansion Metathesis Polymerization for the Synthesis of Cyclic Polyacetylene

Soluble Polymer Precursors via Ring-Expansion Metathesis Polymerization for the Synthesis of Cyclic Polyacetylene

Double Tethered Metallacyclobutane Catalyst for Cyclic Polymer Synthesis

Ring-Expansion Metathesis Polymerization Initiator Design for the Synthesis of Cyclic Polymers

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