Chain propagation and termination mechanisms for polymerization of conjugated polar alkenes by [Al]-based frustrated Lewis pairs

Handle URI:
http://hdl.handle.net/10754/563868
Title:
Chain propagation and termination mechanisms for polymerization of conjugated polar alkenes by [Al]-based frustrated Lewis pairs
Authors:
He, Jianghua; Zhang, Yuetao; Falivene, Laura ( 0000-0003-1509-6191 ) ; Caporaso, Lucia; Cavallo, Luigi ( 0000-0002-1398-338X ) ; Chen, Eugene You Xian
Abstract:
A combined experimental and theoretical study on mechanistic aspects of polymerization of conjugated polar alkenes by frustrated Lewis pairs (FLPs) based on N-heterocyclic carbene (NHC) and Al(C6F5)3 pairs is reported. This study consists of three key parts: structural characterization of active propagating intermediates, propagation kinetics, and chain-termination pathways. Zwitterionic intermediates that simulate the active propagating species in such polymerization have been generated or isolated from the FLP activation of monomers such as 2-vinylpyridine and 2-isopropenyl-2-oxazoline-one of which, IMes+-CH2C(Me)=(C3H2NO)Al(C6F5)3 - (2), has been structurally characterized. Kinetics performed on the polymerization of 2-vinylpyridine by ItBu/Al(C6F5)3 revealed that the polymerization follows a zero-order dependence on monomer concentration and a first-order dependence on initiator (ItBu) and activator [Al(C6F5)3] concentrations, indicating a bimolecular, activated monomer propagation mechanism. The Lewis pair polymerization of conjugate polar alkenes such as methacrylates is accompanied by competing chain-termination side reactions; between the two possible chain-termination pathways, the one that proceeds via intramolecular backbiting cyclization involving nucleophilic attack of the activated ester group of the growing polymer chain by the O-ester enolate active chain end to generate a six-membered lactone (δ-valerolactone)-terminated polymer chain is kinetically favored, but thermodynamically disfavored, over the pathway leading to the -ketoester-terminated chain, as revealed by computational studies.
KAUST Department:
KAUST Catalysis Center (KCC); Physical Sciences and Engineering (PSE) Division; Chemical Science Program
Publisher:
American Chemical Society (ACS)
Journal:
Macromolecules
Issue Date:
25-Nov-2014
DOI:
10.1021/ma5019389
Type:
Article
ISSN:
00249297
Sponsors:
This work was supported by the National Science Foundation (NSF-1150792) for the study carried out at Colorado State University. L.C. thanks the HPC team of Enea for using the ENEA-GRID and the HPC facilities CRESCO in Portici, Italy. We thank Boulder Scientific Co. for the research gift of B(C<INF>6</INF>F<INF>5</INF>)<INF>3</INF> and Dr. Brian Newell for assistance on X-ray structural analysis.
Is Supplemented By:
Jianghua, Zhang, Y., Falivene, L., Caporaso, L., Cavallo, L., & Chen, E. Y.-X. (2014). CCDC 972836: Experimental Crystal Structure Determination [Data set]. Cambridge Crystallographic Data Centre. https://doi.org/10.5517/cc11n9tt; DOI:10.5517/cc11n9tt; HANDLE:http://hdl.handle.net/10754/624285
Appears in Collections:
Articles; Physical Sciences and Engineering (PSE) Division; Chemical Science Program; KAUST Catalysis Center (KCC)

Full metadata record

DC FieldValue Language
dc.contributor.authorHe, Jianghuaen
dc.contributor.authorZhang, Yuetaoen
dc.contributor.authorFalivene, Lauraen
dc.contributor.authorCaporaso, Luciaen
dc.contributor.authorCavallo, Luigien
dc.contributor.authorChen, Eugene You Xianen
dc.date.accessioned2015-08-03T12:17:37Zen
dc.date.available2015-08-03T12:17:37Zen
dc.date.issued2014-11-25en
dc.identifier.issn00249297en
dc.identifier.doi10.1021/ma5019389en
dc.identifier.urihttp://hdl.handle.net/10754/563868en
dc.description.abstractA combined experimental and theoretical study on mechanistic aspects of polymerization of conjugated polar alkenes by frustrated Lewis pairs (FLPs) based on N-heterocyclic carbene (NHC) and Al(C6F5)3 pairs is reported. This study consists of three key parts: structural characterization of active propagating intermediates, propagation kinetics, and chain-termination pathways. Zwitterionic intermediates that simulate the active propagating species in such polymerization have been generated or isolated from the FLP activation of monomers such as 2-vinylpyridine and 2-isopropenyl-2-oxazoline-one of which, IMes+-CH2C(Me)=(C3H2NO)Al(C6F5)3 - (2), has been structurally characterized. Kinetics performed on the polymerization of 2-vinylpyridine by ItBu/Al(C6F5)3 revealed that the polymerization follows a zero-order dependence on monomer concentration and a first-order dependence on initiator (ItBu) and activator [Al(C6F5)3] concentrations, indicating a bimolecular, activated monomer propagation mechanism. The Lewis pair polymerization of conjugate polar alkenes such as methacrylates is accompanied by competing chain-termination side reactions; between the two possible chain-termination pathways, the one that proceeds via intramolecular backbiting cyclization involving nucleophilic attack of the activated ester group of the growing polymer chain by the O-ester enolate active chain end to generate a six-membered lactone (δ-valerolactone)-terminated polymer chain is kinetically favored, but thermodynamically disfavored, over the pathway leading to the -ketoester-terminated chain, as revealed by computational studies.en
dc.description.sponsorshipThis work was supported by the National Science Foundation (NSF-1150792) for the study carried out at Colorado State University. L.C. thanks the HPC team of Enea for using the ENEA-GRID and the HPC facilities CRESCO in Portici, Italy. We thank Boulder Scientific Co. for the research gift of B(C<INF>6</INF>F<INF>5</INF>)<INF>3</INF> and Dr. Brian Newell for assistance on X-ray structural analysis.en
dc.publisherAmerican Chemical Society (ACS)en
dc.titleChain propagation and termination mechanisms for polymerization of conjugated polar alkenes by [Al]-based frustrated Lewis pairsen
dc.typeArticleen
dc.contributor.departmentKAUST Catalysis Center (KCC)en
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.contributor.departmentChemical Science Programen
dc.identifier.journalMacromoleculesen
dc.contributor.institutionDepartment of Chemistry, Colorado State UniversityFort Collins, CO, United Statesen
dc.contributor.institutionState Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin UniversityChangchun, Chinaen
dc.contributor.institutionDipartimento di Chimica e Biologia, Università di Salerno, Via Papa Paolo Giovanni IIFisciano, Italyen
kaust.authorFalivene, Lauraen
kaust.authorCavallo, Luigien
dc.relation.isSupplementedByJianghua, Zhang, Y., Falivene, L., Caporaso, L., Cavallo, L., & Chen, E. Y.-X. (2014). CCDC 972836: Experimental Crystal Structure Determination [Data set]. Cambridge Crystallographic Data Centre. https://doi.org/10.5517/cc11n9tten
dc.relation.isSupplementedByDOI:10.5517/cc11n9tten
dc.relation.isSupplementedByHANDLE:http://hdl.handle.net/10754/624285en
All Items in KAUST are protected by copyright, with all rights reserved, unless otherwise indicated.