N-Heterocyclic Olefins as Initiators for the Polymerization of (Meth)Acrylic Monomers: A Combined Experimental and Theoretical Approach

Handle URI:
http://hdl.handle.net/10754/625426
Title:
N-Heterocyclic Olefins as Initiators for the Polymerization of (Meth)Acrylic Monomers: A Combined Experimental and Theoretical Approach
Authors:
Naumann, Stefan; Mundsinger, Kai; Cavallo, Luigi ( 0000-0002-1398-338X ) ; Falivene, Laura ( 0000-0003-1509-6191 )
Abstract:
The zwitterionic organopolymerization of four different acrylic monomers (N,N-dimethylacrylamide, methyl acrylate, methyl methacrylate and tert-butyl methacrylate) based on neutral initiators, so-called N-heterocyclic olefins (NHOs), is presented. Scope and underlying (deactivation-)mechanisms where studied in a combined experimental and computational effort. From a range of differently structured NHOs it emerged that imidazole-, in contrast to imidazoline- and benzimidazole-derivatives, readily polymerize the selected monomers. While the additive-free reactions proceed with a relatively low degree of control to yield largely atactic material, for the acrylamide the addition of LiCl as µ-type ligand has been shown to result in a rapid and quantitative monomer consumption. The thus generated poly(N,N-dimethyl acrylamide) was found to be highly isotactic (>90% isotactic dyads) with high molecular weight (Mn = 250 000 – 650 000 g/mol, ÐM = 1.3- 1.6). Complementing DFT calculations considered the zwitterionic chain growth with respect to competing side reactions, namely spirocycles and enamine formation. It was found that NHOs with unsaturated backbone better support the zwitterionic chain growth, with the spirocycles acting as dormant species that slow down but do not quench the polymerization process. Contrasting this, enamine formation irreversibly terminates the polymerization and is found to be energetically favored. This pathway can be blocked by introduction of substituents on the exocyclic carbon of the NHO, resulting in structures like 2-isopropylidene-1,3,4,5-tetramethylimidazoline (4) which consequently deliver the most controlled polymerizations. Finally, a good correlation of the initiation energy barrier with the buried volume (%VBur) and the Parr electrophilicity index is described, allowing for a quick and reliable screening of potential monomers based on these two readily accessible parameters.
KAUST Department:
KAUST Catalysis Center (KCC)
Citation:
Naumann S, Mundsinger K, Cavallo L, Falivene L (2017) N-Heterocyclic Olefins as Initiators for the Polymerization of (Meth)Acrylic Monomers: A Combined Experimental and Theoretical Approach. Polym Chem. Available: http://dx.doi.org/10.1039/c7py01226h.
Publisher:
Royal Society of Chemistry (RSC)
Journal:
Polym. Chem.
Issue Date:
25-Aug-2017
DOI:
10.1039/c7py01226h
Type:
Article
ISSN:
1759-9954; 1759-9962
Sponsors:
SN gratefully acknowledges support by the Dr. Leni Schöninger Foundation.
Additional Links:
http://pubs.rsc.org/en/Content/ArticleLanding/2017/PY/C7PY01226H#!divAbstract
Appears in Collections:
Articles; KAUST Catalysis Center (KCC)

Full metadata record

DC FieldValue Language
dc.contributor.authorNaumann, Stefanen
dc.contributor.authorMundsinger, Kaien
dc.contributor.authorCavallo, Luigien
dc.contributor.authorFalivene, Lauraen
dc.date.accessioned2017-08-30T11:40:26Z-
dc.date.available2017-08-30T11:40:26Z-
dc.date.issued2017-08-25en
dc.identifier.citationNaumann S, Mundsinger K, Cavallo L, Falivene L (2017) N-Heterocyclic Olefins as Initiators for the Polymerization of (Meth)Acrylic Monomers: A Combined Experimental and Theoretical Approach. Polym Chem. Available: http://dx.doi.org/10.1039/c7py01226h.en
dc.identifier.issn1759-9954en
dc.identifier.issn1759-9962en
dc.identifier.doi10.1039/c7py01226hen
dc.identifier.urihttp://hdl.handle.net/10754/625426-
dc.description.abstractThe zwitterionic organopolymerization of four different acrylic monomers (N,N-dimethylacrylamide, methyl acrylate, methyl methacrylate and tert-butyl methacrylate) based on neutral initiators, so-called N-heterocyclic olefins (NHOs), is presented. Scope and underlying (deactivation-)mechanisms where studied in a combined experimental and computational effort. From a range of differently structured NHOs it emerged that imidazole-, in contrast to imidazoline- and benzimidazole-derivatives, readily polymerize the selected monomers. While the additive-free reactions proceed with a relatively low degree of control to yield largely atactic material, for the acrylamide the addition of LiCl as µ-type ligand has been shown to result in a rapid and quantitative monomer consumption. The thus generated poly(N,N-dimethyl acrylamide) was found to be highly isotactic (>90% isotactic dyads) with high molecular weight (Mn = 250 000 – 650 000 g/mol, ÐM = 1.3- 1.6). Complementing DFT calculations considered the zwitterionic chain growth with respect to competing side reactions, namely spirocycles and enamine formation. It was found that NHOs with unsaturated backbone better support the zwitterionic chain growth, with the spirocycles acting as dormant species that slow down but do not quench the polymerization process. Contrasting this, enamine formation irreversibly terminates the polymerization and is found to be energetically favored. This pathway can be blocked by introduction of substituents on the exocyclic carbon of the NHO, resulting in structures like 2-isopropylidene-1,3,4,5-tetramethylimidazoline (4) which consequently deliver the most controlled polymerizations. Finally, a good correlation of the initiation energy barrier with the buried volume (%VBur) and the Parr electrophilicity index is described, allowing for a quick and reliable screening of potential monomers based on these two readily accessible parameters.en
dc.description.sponsorshipSN gratefully acknowledges support by the Dr. Leni Schöninger Foundation.en
dc.publisherRoyal Society of Chemistry (RSC)en
dc.relation.urlhttp://pubs.rsc.org/en/Content/ArticleLanding/2017/PY/C7PY01226H#!divAbstracten
dc.rightsArchived with thanks to Polym. Chem.en
dc.titleN-Heterocyclic Olefins as Initiators for the Polymerization of (Meth)Acrylic Monomers: A Combined Experimental and Theoretical Approachen
dc.typeArticleen
dc.contributor.departmentKAUST Catalysis Center (KCC)en
dc.identifier.journalPolym. Chem.en
dc.eprint.versionPost-printen
dc.contributor.institutionDepartment of Polymer Chemistry, University of Stuttgart, 70569 Stuttgart, Germanyen
kaust.authorCavallo, Luigien
kaust.authorFalivene, Lauraen
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