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Title: Ring-Opening Polymerization of Cyclic Esters and Carbonates with (Thio)urea/Cyclopropenimine Organocatalytic Systems
Organocatalyzed ring-opening polymerization is a powerful tool for the synthesis of a variety of functional readily degradable polyesters and polycarbonates. We report the use of (thio)ureas in combination with cyclopropenimine bases as unique catalyst for the polymerization of cyclic esters and carbonates with a large span of reactivities. Methodologies of exceptionally effective and selective cocatalyst combinations were devised to produce polyesters and polycarbonates with narrow dispersity (Đ = 1.01 – 1.10). Correlations of the pKa of the various ureas and cyclopropenimine bases revealed the critical importance of matching the pKa of the two cocatalysts to achieve the most efficient polymerization conditions. It was found that promoting strong H-bonding interactions with a noncompetitive organic solvent, such as CH2Cl2, enabled greatly accelerated polymerization rates. The stereoselective polymerization of rac-lactide afforded stereoblock poly(lactides) that crystallize as stereocomplexes, as confirmed by wide-angle x-ray scattering.  more » « less
Award ID(s):
2002933
PAR ID:
10545579
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ;
Editor(s):
Rowan, Stuart J
Publisher / Repository:
ACS Macro Letters
Date Published:
Journal Name:
ACS Macro Letters
Volume:
13
Issue:
2
ISSN:
2161-1653
Page Range / eLocation ID:
181-188
Subject(s) / Keyword(s):
ring-opening polymerization organocatalysis
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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