Strategies Toward Sequential Polymerization of Different Types of
Heterocyclic Monomers Using Organic Catalysts
Junpeng Zhao, David Pahovnik, Nikos Hadjichristidis
Polymer Synthesis Laboratory, KAUST Catalysis Center, Physical Sciences and Engineering Division, King
Abdullah University of Science and Technology (KAUST), Thuwal 23955, Saudi Arabia
E-mail: [email protected]
Ring-opening polymerizations (ROP) of epoxides and cyclic esters/carbonates share the
common feature of proceeding through alkoxide/hydroxyl end groups, but one-pot sequential
polymerization of such different types of monomers has been a major challenge as the active
species that work for one can either be inactive or lead to uncontrolled polymerization for the
other, especially in the case of conventional metal-based initiating/catalytic systems.
The development of organocatalytic polymerization techniques has offered new opportunities
for the fulfillment of such synthetic tasks. Recently, we have found that controlled sequential
polymerization can be performed leading to well-defined block copolymers provided the
organic catalysts are adequately chosen and finely tuned to the monomers to polymerize. For
example, the use of a mild phosphazene base1 enables the sequential ROP of ethylene oxide,
ε-caprolactone and L-lactide to generate the corresponding triblock terpolymer (Figure 1a),2
and a “catalyst switch” strategy (a successive use of a strong phosphazene base and an acid
catalyst) enables the one-pot synthesis of well-defined block copolymers based on various
polyethers, polyesters and polycarbonates with 2, 3 or 4 block types (Figure 1b).3,4
Figure 1. Sequential organocatalytic polymerization of different types of heterocyclic
monomers using (a) a mild phosphazene base and (b) a “catalyst switch” strategy.
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J. Zhao, N. Hadjichristidis, Y. Gnanou, Polimery, 2014, 59, 49-59.
J. Zhao, D. Pahovnik, Y. Gnanou, N. Hadjichristidis, Polym. Chem., 2014, 5, 3750-3753.
J. Zhao, D. Pahovnik, Y. Gnanou, N. Hadjichristidis, Macromolecules, 2014, 47, 3814-3822.
J. Zhao, D. Pahovnik, Y. Gnanou, N. Hadjichristidis, J. Polym. Sci. Part A: Polym. Chem. 2014, DOI:
10.1002/pola.27332.