Phosphazene bases for the organocatalytic living ring-opening polymerization of cyclic esters

POLY 484

Lei Zhang, leizhang@us.ibm.com1, Fredrik Nederberg, fredrikn@us.ibm.com1, Russell Pratt1, Robert Waymouth2, James L. Hedrick1, and Charles G. Wade1. (1) IBM Almaden Research Center, 650 Harry Road, San Jose, CA 95120, (2) Department of Chemistry, Stanford University, Stanford, CA 94305
We demonstrate that phosphazene base 2-tert-butylimino-2-diethylamino-1,3-dimethyl-perhydro-1,3,2-diazaphosphorine (BEMP) is an active organocatalysts for the living ring-opening polymerization (ROP) of cyclic esters. Polyesters prepared through this organocatalytic route possess predictable molecular weights, narrow polydispersities, and high end-group fidelity. Mechanistic studies suggest that the intermolecular hydrogen bonding of the alcohol initiator to phosphazene bases activates the alcohol for ROP of cyclic esters.