Step-growth polymerisation of alkyl acrylates <i>via</i> concomitant oxa-Michael and transesterification reactions

Ratzenböck, Karin; Pahovnik, David; Slugovc, Christian

doi:10.1039/d0py01271h

Cited by 15 publications

(21 citation statements)

References 23 publications

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“…Considering the distinctly higher doublebond conversions at 80 °C, these findings point to another double-bond consuming reaction beside the oxa-Michael reaction. The evaluation of the NMR spectra indicate, among repeating units from oxa-Michael and transesterification reactions [30,31], the presence of Rauhut-Currier-derived linkages [32][33][34]. This repeat unit is characterized by peaks at 6.22 and 5.64 ppm in the 1 H NMR spectrum and at 126.6, 33.0, 27.3 ppm in the 13 C NMR spectrum of poly4 (see Supporting Information File 1) and its share is with approximately 17-20% higher in polymers prepared at 80 °C (Figure 2).…”

Section: Resultsmentioning

confidence: 99%

“…1 13 C, respectively). 31 P NMR measurements were performed on a Varian Inova 500 MHz instrument operating at 202.547 MHz. Chemical shifts are reported in ppm relative to an external standard (85% H 3 PO 4 ).…”

Section: Experimental General Informationmentioning

confidence: 99%

“…Figure 3: Left: Oxidation stability of the phosphines. Phosphine oxide content in % as determined by31 P NMR spectroscopy after a 14 d exposure to air under the following conditions: sample stored as a solid at room temperature, samples dissolved in chloroform and 1-hexanol (stored at room temperature in the dark), and in 1-hexanol (stored at 80 °C in the dark). Right: Relative stabilities of the zwitterions formed upon reaction of Michael acceptors 1-3 with the phosphines (the cartoon shows the structures of the educts acrylonitrile and TMTPP (left, behind the chart) and the corresponding zwitterion (right, above), optimized at the B3LYP/def2-TZVPPD level of theory).…”

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Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions

Fischer¹,

Renner²,

Boese³

et al. 2021

Beilstein J. Org. Chem.

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Electron-rich triarylphosphines, namely 4-(methoxyphenyl)diphenylphosphine (MMTPP) and tris(4-trimethoxyphenyl)phosphine (TMTPP), outperform commonly used triphenylphosphine (TPP) in catalyzing oxa-Michael additions. A matrix consisting of three differently strong Michael acceptors and four alcohols of varying acidity was used to assess the activity of the three catalysts. All test reactions were performed with 1 mol % catalyst loading, under solvent-free conditions and at room temperature. The results reveal a decisive superiority of TMTPP for converting poor and intermediate Michael acceptors such as acrylamide and acrylonitrile and for converting less acidic alcohols like isopropanol. With stronger Michael acceptors and more acidic alcohols, the impact of the more electron-rich catalysts is less pronounced. The experimental activity trend was rationalized by calculating the Michael acceptor affinities of all phosphine–Michael acceptor combinations. Besides this parameter, the acidity of the alcohol has a strong impact on the reaction speed. The oxidation stability of the phosphines was also evaluated and the most electron-rich TMTPP was found to be only slightly more sensitive to oxidation than TPP. Finally, the catalysts were employed in the oxa-Michael polymerization of 2-hydroxyethyl acrylate. With TMTPP polymers characterized by number average molar masses of about 1200 g/mol at room temperature are accessible. Polymerizations carried out at 80 °C resulted in macromolecules containing a considerable share of Rauhut–Currier-type repeat units and consequently lower molar masses were obtained.

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Section: Resultsmentioning

confidence: 99%

Section: Experimental General Informationmentioning

confidence: 99%

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confidence: 99%

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Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions

Fischer¹,

Renner²,

Boese³

et al. 2021

Beilstein J. Org. Chem.

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“…Considering the distinctly higher double bond conversions at 80 °C, these findings point to another double bond consuming reaction beside the oxa-Michael reaction. Evaluation of the NMR spectra indicate, among repeating units from oxa-Michael and transesterification reactions, 28,29 the presence of Rauhut-Currier derived linkages. 30,31,32 This repeat unit is characterized by peaks at 6.22 and 5.64 ppm in the 1 H-NMR spectrum and at 126.6, 33.0, 27.3 ppm in the 13 C-NMR spectrum of poly4 (see Supporting Information) and its share is with approximately 17-20% higher in polymers prepared at 80 °C (Figure 2).…”

Section: Resultsmentioning

confidence: 99%

Electron Rich Triarylphosphines as Nucleophilic Catalysts for Oxa-Michael Reactions

Fischer¹,

Renner²,

Boese³

et al. 2021

Preprint

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Herein, we study the activity of methoxysubstituted arylphosphines (4-methoxy-phenyl)diphenylphosphine (MMTPP) and tris(4-trimethoxyphenyl)phosphine (TMTPP) in catalyzing oxa-Michael additions in comparison to commonly used triphenylphosphine (TPP). Acrylonitrile, acryl amide and divinyl sulfone are used as Michael acceptors and propargyl alcohol, allyl alcohol, n-propanol and i-propanol are assessed as Michael donors. In many cases, catalyst loadings of only 1 mol% in respect to the Michael acceptor are sufficient to provide full conversion towards the Michael adduct in 24 h at room temperature. Generally, TMTPP is the most active catalyst in all cases. The experimental activity trend was rationalized by calculating the Michael acceptor affinities of all phosphine – Michael acceptor combinations. Besides this parameter, the acidity of the alcohol has a strong impact on the reaction speed. The oxidation stability of the phosphines was evaluated and electron richest TMTPP was found to be only slightly more sensitive to oxidation than TPP. Finally, the catalysts were employed in the oxa-Michael polymerization of 2-hydroxyethyl acrylate. With TMTPP polymers characterized by number average molar masses of about 1200 g/mol at room temperature are accessible. Polymerizations carried out at 80 °C resulted in macromolecules containing a considerable share of Rauhut-Currier type repeat units and consequently lower molar masses were obtained.

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“…Several minor series were observed, including a PA 3 series terminated with DBU or a PA 3 series terminated with a decomposition product of DBU. 20 , 21 SEC-MALS investigations in DMSO (containing LiBr) were carried out to determine the absolute molar mass averages of branched PA 3 in dependence of the DBU loading. The molar mass averages increased with decreasing DBU content pointing to a chain-growth like mechanism of the polymerization.…”

Section: Resultsmentioning

confidence: 99%

Melt-Polymerization of Acrylamide Initiated by Nucleophiles: A Route Towards Highly Branched and Amorphous Polyamide 3

Edinger¹,

Weber²,

Žagar³

et al. 2020

Preprint

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The melt-polymerization of acrylamide initiated by nucleophiles allows for the preparation of polyamide 3 (PA 3) with a branching factor of about 1.5. The high share of branching units imparts a fully amorphous morphology featuring a low glass transition temperature of 67 °C and renders the polymer water soluble. The disclosed method provides an easy, resource-efficient and green access to a polymer interesting for applications in biological and biomedical systems. The obtained PA 3 was characterized by several NMR-techniques, MALDI-TOF mass spectrometry, size-exclusion chromatography, thermal analyses and powder-X-ray diffractometry. Preparation and characterization of a 15N-marked polymer complemented the elucidation of the polymers structure. Mechanistically, the polymerization can be considered as an aza-Michael polymerization of acrylamide involving zwitter-ionic species as the key intermediates being responsible for the high degree of branching. <br>

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Step-growth polymerisation of alkyl acrylates via concomitant oxa-Michael and transesterification reactions

Abstract: An auto-tandem catalytic approach towards the preparation of poly(ester–ether)s from simple alkyl acrylates and diols is introduced.

Cited by 15 publications

References 23 publications

Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions

Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions

Electron Rich Triarylphosphines as Nucleophilic Catalysts for Oxa-Michael Reactions

Melt-Polymerization of Acrylamide Initiated by Nucleophiles: A Route Towards Highly Branched and Amorphous Polyamide 3

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