The synthesis of hybrid bioconjugates via the ring‐opening polymerization (ROP) of N‐carboxyanhydrides (NCAs) using a synthetic macroinitiator is described. Poly(n‐butyl acrylate), polystyrene, and poly(N‐isopropyl acrylamide) are synthesized (polydisperity index, Đ < 1.1) using reversible addition–fragmentation chain transfer (RAFT) as the synthetic tool. A phthalimidomethyl trithiocarbonate RAFT chain transfer agent is used to prepare well‐defined, end‐functional polymers, which after deprotection result in amine terminal macroinitiators. The subsequent initiating systems could successfully be chain extended with ε‐benzyloxycarbonyl‐l ‐lysine or γ‐benzyl‐l ‐glutamate as the NCAs to produce a library of polymer–polypeptide conjugates. In doing so, a novel procedure for directly synthesizing bioconjugates via a non‐modular route without the need for excessive purification and isolation steps is described.
