This contribution reports the first successful coordination-addition polymerization of N,Ndialkylmethacrylamides and the first example of kinetic resolution of a racemic methacrylamide by chiral metallocene catalysts. The polymerization of methacryloyl-2-methylaziridine (MMAz) by rac-(EBI)Zr+- (THF)[OC(OiPr)dCMe2][MeB(C6F5)3]- (1) is stereospecific and also exhibits a high degree of control over polymerization. This polymerization follows first-order kinetics in both concentrations of monomer and catalyst, consistent with a monometallic propagation mechanism involving the fast step of intramolecular conjugate addition within the catalyst-monomer coordination complex leading to the eight-membered-ring resting intermediate. Substituents on the highly strained aziridine ring stabilize the aziridine moiety against thermally induced crosslinking through its ring-opening reaction; thus, the polymer derived from methacryloyl-tetramethyleneaziridine (MTMAz) exhibits greatly enhanced resistance toward thermal cross-linking over poly(MMAz), marking 57 and 42 °C higher onset cross-linking and maximum cross-linking temperatures, respectively. Enantiomeric catalyst (S,S)-1 demonstrates experimentally and theoretically its ability to kinetically resolve the racemic MMAz monomer with a low stereoselectivity factor s of 1.8. Polymerizability of several methacrylamide monomers has been investigated via a combined experimental and theoretical (DFT) study that examines the degree of conjugation between the vinyl and carbonyl double bonds, relative polymerization reactivity, and relative energy for the formation of amide-enolate intermediates.

Coordination-Addition Polymerization and Kinetic Resolution of Methacrylamides by Chiral Metallocene Catalysts

CAPORASO, Lucia;CAVALLO, LUIGI;
2009-01-01

Abstract

This contribution reports the first successful coordination-addition polymerization of N,Ndialkylmethacrylamides and the first example of kinetic resolution of a racemic methacrylamide by chiral metallocene catalysts. The polymerization of methacryloyl-2-methylaziridine (MMAz) by rac-(EBI)Zr+- (THF)[OC(OiPr)dCMe2][MeB(C6F5)3]- (1) is stereospecific and also exhibits a high degree of control over polymerization. This polymerization follows first-order kinetics in both concentrations of monomer and catalyst, consistent with a monometallic propagation mechanism involving the fast step of intramolecular conjugate addition within the catalyst-monomer coordination complex leading to the eight-membered-ring resting intermediate. Substituents on the highly strained aziridine ring stabilize the aziridine moiety against thermally induced crosslinking through its ring-opening reaction; thus, the polymer derived from methacryloyl-tetramethyleneaziridine (MTMAz) exhibits greatly enhanced resistance toward thermal cross-linking over poly(MMAz), marking 57 and 42 °C higher onset cross-linking and maximum cross-linking temperatures, respectively. Enantiomeric catalyst (S,S)-1 demonstrates experimentally and theoretically its ability to kinetically resolve the racemic MMAz monomer with a low stereoselectivity factor s of 1.8. Polymerizability of several methacrylamide monomers has been investigated via a combined experimental and theoretical (DFT) study that examines the degree of conjugation between the vinyl and carbonyl double bonds, relative polymerization reactivity, and relative energy for the formation of amide-enolate intermediates.
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11386/2600357
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo

Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 33
  • ???jsp.display-item.citation.isi??? 32
social impact