Functional
poly(amino acid)s such as poly(ε-lysine) have
many potential high-value applications. However, the effective chemosynthetic
strategy for these materials remains a big challenge in polymer chemistry;
the key issue is how to design and protect amino groups for the effective
ring-opening polymerization (ROP). Our lab succeeded in chemosynthesis
of poly(ε-lysine) via delicate design of a 2,5-dimethylpyrrole
protecting group and metal-catalyzed ROP processes, but harsh reaction
conditions (e.g., ca. 260 °C) were required. Herein, we developed
a superbase t-BuP4-catalyzed ROP of ε-lactam
derivatives, affording high molecular weight poly(ε-lysine)
bearing pendant protected amino groups with high monomer conversion
(up to 95%). The organocatalytic polymerization could proceed at low
reaction temperature (e.g., 60 °C) compatible with readily removable
protecting groups, providing a sustainable and new methodology toward
facile preparation of poly(ε-lysine).
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