Chain and Step Growth Polymerizations of Cyclic Imino Ethers: From Poly(2-oxazoline)s to Poly(ester amide)s

Cyclic imino ethers (CIEs), such as 2-oxazolines and 2-oxazines are a unique class of monomers, which because of their manifold reactivities can be polymerized via multiple techniques. Most prominent, the living cationic ring-opening polymerization (CROP) of CIEs enables the synthesis of well-defined tailor-made poly(CIEs), which have tremendous importance as functional and biocompatible polymers. On the other hand, CIEs are also powerful monomers in polyadditions resulting in the formation of a variety of biodegradable polyamide-based systems. In this contribution, the enormous potential of CIEs as functional building blocks is discussed, which goes well beyond the CROP. Besides trends in the CROP of CIEs, recent developments in step-growth polymerizations of CIEs are highlighted, including the spontaneous zwitterionic copolymerization (SZWIP) which provides access to functional alternating N-acylated poly(amino ester)s (NPAEs) and polyadditions of multifunctional CIEs which give main-chain poly(ester amide)s (PEAs).