Catechol Acetonide Glycidyl Ether (CAGE): A Functional Epoxide Monomer for Linear and Hyperbranched Multi-Catechol Functional Polyether Architectures

A protected catechol-containing epoxide monomer, catechol acetonide glycidyl ether (CAGE), is introduced. CAGE is conveniently obtained in three steps and enables the incorporation of surface-active catechol moieties into a broad variety of hydrophilic and biocompatible polyether architectures by copolymerization. Via acidic cleavage of the acetal protecting groups, the polymer-attached catechol functionalities are liberated and available for surface attachment or metal complexation. CAGE has been copolymerized with ethylene oxide and glycidol to obtain both linear poly(ethylene glycol) and hyperbranched polyglycerol copolymers, respectively, with multiple surface-adhesive catechol moieties. The CAGE content in the copolymers was varied from 1 to 16%, and all polymers exhibit moderate polydispersity (linear: Mw/Mn = 1.05–1.33; hyperbranched: Mw/Mn = 1.44–1.86). In situ kinetic studies of the simultaneous copolymerization of EO and CAGE via NMR spectroscopy have been performed to determine the microstructure of the linear poly(ethylene oxide-co-catechol acetonide glycidyl ether), P(EO-co-CAGE), copolymers. EO shows slightly higher reactivity than CAGE (rEO = 1.14, rCAGE = 0.88), leading to an almost ideally random copolymerization. Because of the catechol units, the copolymers form pH-induced cross-linked networks through metal–ligand interactions. ABA triblock copolymers of the type PCAGE-b-PEG-b-PCAGE formed highly swellable hydrogels upon addition of FeCl3. Furthermore, static water contact angle measurements demonstrate an increase in the hydrophilicity of iron, PTFE, and PVC surfaces after coating with catechol-functional mf-PEGs.