Polymerization of Epoxides at a Static Oil-Alkaline Water Interface.

'On-water' catalysis entails the significant enhancement of a chemical reaction by water, even when those reactions are known to be water-sensitive. Here, the findings about the anionic ring opening polymerization of epoxides at the static interface between oil and alkaline water are shared. Unexpectedly, high molar mass fractions are observed with the interfacial system presented herein, albeit at very low conversions (< 5%). Styrene oxide, a notably unreactive epoxide, is chosen as the model compound to investigate the influence of several reaction parameters (i.e., pH, type of the initiator salt, polymerization time, interfacial area, solvent, shaking) on the polymerization. Poly(styrene oxide) (PSO) with an M of 5300 g mol is observed via MALDI-ToF MS, with species of at least 8000 g mol. The feasibility of expanding the system to (cyclic) aliphatic and aromatic epoxides, and glycidyl ethers is also explored. The system appears to promote polymerization of epoxides that position at the interface, in such a way that initiation and propagation can occur. A mechanistic interpretation of the interfacial polymerization is suggested. The surprising results obtained in this work urge to revisit the role of water in ionic polymerizations.