Photoresponsive cryogels based on poly(2-oxazoline)s

Abstract

Herein, we present the synthesis of two poly(2-oxazoline)-based photodegradable cross-linkers. For that 1-(piperazin-1-yl)ethan-1-one-O-methacryloyl oxime (PipOxim) was synthesized as new photocleavable, polymerizable endcapping agent for the termination of the cationic ring-opening polymerization (CROP) of 2-ethyl-2-oxazoline (EtOx), to yield in the bifunctional cross-linker B-Et(10)PipOxim. Secondly, bifunctional poly(2-ethyl-2-oxazoline)s (PEtOx) carrying photocleavable, polymerizable triazene phenyl methacrylate (TAz) ω-end groups were prepared by post-polymerization functionalization (B-Et(10,20,40)TAz). The process of decomposition under UV–Vis irradiation was successfully demonstrated for all cross-linkers that had been produced using UV–Vis spectroscopy. From the photodegradable POx-based cross-linkers, cryogels were prepared with 100% of the two different cross-linkers. Additionally, mixed cryogels made of B-Et(40)TAz and acrylic acid were produced. All cryogels were characterized by thermogravimetric analysis (TGA), solid-state NMR (ssNMR), scanning electron microscopy (SEM) and swelling investigations. Notably, the use of 92 mol% acrylic acid led to the formation of cryogels susceptible to a complete dissolution in water after exposure to UV–Vis light.