Network formation by aza-Michael addition of primary amines to vinyl end groups of enzymatically synthesized poly(glycerol adipate)

Abstract

A highly efficient approach for the synthesis of polyester-based networks via aza-Michael addition of primary amines to α,β-unsaturated (vinyl) end groups of poly(glycerol adipate) (PGA) was achieved. By acylation of PGA with 6-(Fmoc-amino)hexanoic acid side chains via Steglich esterification, protected amine-functionalized PGA was obtained. This was followed by the removal of fluorenylmethyloxycarbonyl (Fmoc) protecting groups and the synthesis of PGA-based networks under catalyst-free conditions. The successful conjugate addition of primary amines to vinyl end groups and network formation were confirmed using 13C magic angle spinning NMR and Fourier transform infrared spectroscopy. Network heterogeneity and defects were quantitatively investigated using 1H double-quantum NMR spectroscopy. Finally, a hydrogel was prepared with potential biomedical applications.