Economically competitive Organic Acid-Base mixtures as Catalysts for the Self-Condensation of Diols into Polyethers

Abstract

Organocatalysts are used in a wide range of polymerization reactions with the advantage of being often more benign or sustainable, while maintaining high catalytic activity. However, the low thermal stability of most of these compounds remain an obstacle for high temperature reactions. It was recently reported that complexes formed from a base such 1,4,7-triazabicyclodecene (TBD) and an acid such as methane sulfonic acid (MSA) demonstrate high thermal stability while efficiently catalysing polycondenzation reactions. However, TBD is not cost-efficient neither available at industrial scale, which makes it unfit for scaling up. Herein, eight different bases have been investigated as to replace TBD. First, we confirm the complex formation between the MSA and the bases by nuclear magnetic spectroscopy while confirming the thermal stability of the mixtures by thermogravimetric analysis before evaluating their catalytic activity in the self-condensation of 1,6-hexanediol. Among the different investigated bases, 1,1,3,3-tetramethyl guanidine (TMG) appeared to be the best option since it gathers both high thermal stability and good catalytic activity. These characteristics make TMG suitable for replacing TBD in the self-condensation of diols while opening the way for being used in a wide range of high temperature (de)polymerization reactions.