N-Heterocyclic carbene/Lewis acid-mediated ring-opening polymerization of propylene oxide. Part 2: Toward dihydroxytelechelic polyethers using triethylborane

Propylene oxide (PO) is polymerized by metal-free ring-opening 11 polymerization (ROP) at 25 °C using N-heterocyclic carbenes (NHCs) and 12 triethylborane (Et 3 B) as a bicomponent catalytic system. Poly(propylene oxide)s with 13 predictable molar mass up to 60 000 g.mol-1 and low dispersity (Ð < 1.10) were 14 obtained without the occurrence of undesirable transfer reaction to the monomer. In 15 presence of an alcohol as the initiator, the ROP of PO follows an anionic mechanism 16 assisted by monomer activation improving the efficiency of NHCs for the 17 polymerization of substituted epoxides. Et 3 B is involved both in the formation of a 18 complexed active center and in the activation of PO. Interestingly, 19 dihydroxytelechelic PPOs can be readily synthesized not only using 1,4-20 benzenedimethanol but also water, both serving as difunctional initiators. Bloc