Abstract At first glance, the sequential ring-opening polymerization (ROP) of epoxides and cyclic esters seems facile and the synthesis of the corresponding block co-/ter-/quarto-polymers appears straightforward. However, initiating/catalytic systems that work for epoxides, typically alkali alkoxides, provoke chain transfer reactions in the case of cyclic esters, and those that are appropriate for the latter, typically tin or aluminum alkoxides, are irrelevant for the former. The same is valid in the case of organocatalysts such as phosphazene bases. For example, t-BuP4, one of the strongest phosphazene bases, is well suited for the polymerization of epoxides but brings about extensive chain transfer reactions in the case of cyclic esters. By using a mild phosphazene base (t-BuP2), as the common catalyst and monohydroxyl compound or water as initiators, we were able to synthesize in one-pot well-defined triblock and pentablock terpolymers of ethylene oxide (EO), ε-caprolactone (CL) and L-lactide (LLA). The drawback of this strategy is the long polymerization time of EO (three days) and that no other (substituted) epoxides can be polymerized by t-BuP2. On the other hand, strong organic acids, such as diphenyl phosphate (DPP) have been employed to afford well-controlled ROP of cyclic esters/carbonates via either a monomer activation mechanism or a monomer/chain end dual activation mechanism. By combining the ideal superbase catalyst (t-BuP4) for epoxides and the ideal organic superacid catalyst (DPP) for cyclic esters/carbonates into a novel “catalyst switch” strategy, where DPP acts as both base neutralizer and catalyst (excess), we were successful synthesizing in one-pot well-defined co-/ter-/quarto linear and 3-arm star polymers. References J. Zhao, D. Pahovnik, Y. Gnanou, N. Hadjichristidis, Polym. Chem. 2014, 5, 3750 J. Zhao, D. Pahovnik, Y. Gnanou, N. Hadjichristidis, Macromolecules 2014, 47, 3814

Sequential one-pot organocatalytic polymerization of epoxides and cyclic esters/carbonates

249th National Meeting (2015)

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