TY - JOUR
T1 - Stereoretention in the Bulk ROP of l -Lactide Guided by a Thermally Stable Organocatalyst
AU - Basterretxea, Andere
AU - Gabirondo, Elena
AU - Jehanno, Coralie
AU - Zhu, Haijin
AU - Coulembier, Olivier
AU - Mecerreyes, David
AU - Sardon, Haritz
N1 - Publisher Copyright:
© 2021 American Chemical Society.
PY - 2021/7/13
Y1 - 2021/7/13
N2 - Polylactide (PLA) has emerged as one of the most promising bio-based alternatives to petroleum-based plastics, mainly because it can be produced from the fermentation of naturally occurring sugars and because it can be industrially compostable. In spite of these benefits, the industrial ring-opening polymerization (ROP) of l-lactide (L-LA) still requires the use of highly active and thermally stable metal-based catalysts, which have raised some environmental concerns. While the excellent balance between activity and functional group compatibility of organic acid catalysts makes them some of the most suitable catalysts for the metal-free ROP of L-LA, the majority of these acids are highly volatile and subject to decomposition at high temperature, which limits their use under industrially relevant conditions. In this work we exploit the use of a nonstoichiometric acid-base organocatalyst to promote the solvent-free and metal-free ROP of L-LA at elevated temperatures in the absence of epimerization and transesterification. To do so, a stable acidic complex was prepared by mixing 4-(dimethylamino)pyridine (DMAP) with 2 equiv of methanesulfonic acid (MSA). Both experimental and computational results indicate that DMAP:MSA (1:2) not only is highly thermally stable but also promotes the retention of stereoregularity during the polymerization of L-LA, leading to PLLA with a molar mass of up to 40 kg mol-1 and a chiral purity in excess of 98%. This result provides a new feature to exploit in organocatalyzed polymerization and in the design of new catalysts to facilitate the path to market.
AB - Polylactide (PLA) has emerged as one of the most promising bio-based alternatives to petroleum-based plastics, mainly because it can be produced from the fermentation of naturally occurring sugars and because it can be industrially compostable. In spite of these benefits, the industrial ring-opening polymerization (ROP) of l-lactide (L-LA) still requires the use of highly active and thermally stable metal-based catalysts, which have raised some environmental concerns. While the excellent balance between activity and functional group compatibility of organic acid catalysts makes them some of the most suitable catalysts for the metal-free ROP of L-LA, the majority of these acids are highly volatile and subject to decomposition at high temperature, which limits their use under industrially relevant conditions. In this work we exploit the use of a nonstoichiometric acid-base organocatalyst to promote the solvent-free and metal-free ROP of L-LA at elevated temperatures in the absence of epimerization and transesterification. To do so, a stable acidic complex was prepared by mixing 4-(dimethylamino)pyridine (DMAP) with 2 equiv of methanesulfonic acid (MSA). Both experimental and computational results indicate that DMAP:MSA (1:2) not only is highly thermally stable but also promotes the retention of stereoregularity during the polymerization of L-LA, leading to PLLA with a molar mass of up to 40 kg mol-1 and a chiral purity in excess of 98%. This result provides a new feature to exploit in organocatalyzed polymerization and in the design of new catalysts to facilitate the path to market.
UR - http://www.scopus.com/inward/record.url?scp=85110069297&partnerID=8YFLogxK
U2 - 10.1021/acs.macromol.1c01060
DO - 10.1021/acs.macromol.1c01060
M3 - 文章
AN - SCOPUS:85110069297
SN - 0024-9297
VL - 54
SP - 6214
EP - 6225
JO - Macromolecules
JF - Macromolecules
IS - 13
ER -