Unexpected efficiency of cyclic amidine catalysts in depolymerizing poly(ethylene terephthalate) (pages 1606–1611)
Kazuki Fukushima, Daniel J. Coady, Gavin O. Jones, Hamid A. Almegren, Abdullah M. Alabdulrahman, Fares D. Alsewailem, Hans W. Horn, Julia E. Rice and James L. Hedrick
Article first published online: 9 JAN 2013 | DOI: 10.1002/pola.26530
This article describes the studies on the catalytic activity of several nitrogen-based organic catalysts for the depolymerization of poly(ethylene terephthalate) (PET), in which a few cyclic amidines work more effectively than a potent, bifunctional guanidine-based catalyst 1,5,7-triazabicyclo-[4,4,0]-dec-5-ene (TBD) in the presence of short-chain diols that play a role in activation of carbonyl groups through hydrogen bonding. Further studies show that the catalytic efficiency at the above specific conditions depends only on the extent of activation of a hydroxyl group rather than simply the pKa of the bases. For glycolysis with excess short-chain alkanediols, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) is the best catalyst. In contrast, TBD shows outstanding catalytic activity in depolymerizations of PET with mono-alcohols and longer-chain diols.