N-heterocyclic carbenes as organocatalysts in controlled/living ring-opening polymerization ofO-carboxyanhydrides derived froml-lactic acid andl-mandelic acid

Abstract

An organocatalytic approach to controlled/living ring-opening polymerizations (ROPs) of O-carboxyanhydrides (OCAs) using N-heterocyclic carbenes (NHCs) as nucleophilic catalysts has been investigated. NHCs with different structures were used in order to compare the catalytic performances in the ROP of OCA of L-lactic acid.1 H NMR, SEC, and MALDI-TOF MS measurements of the products clearly indicated a controlled/living manner of the polymerization. The controlled/living nature was further confirmed by kinetic and chain extension experiments. Additionally, polylol initiators were used to produce a,x-dihydroxy telechelic, 3-, and 4-armed starshaped polymers. Moreover, star-shaped diblock copolymer, bearing methyl and phenyl side groups, has been successfully synthesized with OCA/NHC system.

Living Ring-Opening Polymerization of O-Carboxyanhydrides: The Search for Catalysts

“…In 2006, the Bourissou group started to apply the organocatalysts that had achieved success in the ROP of lactones to OCA polymerization (du Boullay et al, 2006). Over the years, both DMAP and N -heterocyclic carbenes (NHCs) have been utilized for the ROP of OCAs ( 1 , 2 , 6 , 8 ) and obtained reasonable results (du Boullay et al, 2006, 2008; Lu Y. et al, 2012; Zhang et al, 2012; Chen et al, 2014; Xia et al, 2014). However, most polymers catalyzed by organocatalysts exhibited MWs <30 kDa or low DPs (≤200) (Martin Vaca and Bourissou, 2015).…”

Update and challenges in organo-mediated polymerization reactions

“…) [118]. All these carbenes allowed polymerizing L-lacOCA in THF at r.t., yielding poly(L-lacOCA) of controlled molar masses (Mn = 1,100 -12,700 g.mol -1 ; Đ = 1.10-1 41)…”

Controlled Ring-Opening Polymerization of O-Carboxyanhydrides to Synthesize Functionalized Poly(α-Hydroxy Acids)

“…Finding success in the ROP of lactones, NHCs, including imidazolium carbenes and triazolium carbenes, were effectively applied to the living ROP of L-4 with feeding ratios (FRs) up to 200/1. 48 A panel of substituted NHC catalysts was investigated and lesssterically hindered NHCs were observed to have higher catalytic activity but less thermal stability, weaker control of polymerization, and more likely to dimerize. Star-shaped diblock copolymer of L-4 and L-5 were also synthesized using NHC.…”