Oxime functionalization strategy for iodinated poly(epsilon-caprolactone) X-ray opaque materials

Since two of the most common technologies for imaging the human body are X-ray radiography and computed tomography (CT), researchers are focused on developing biodegradable and biocompatible polymeric molecules as an alternative to the traditional small molecule contrast agents. This report highlights the synthesis of novel biodegradable iodinated poly(ε-caprolactone) copolymers by oxime "Click" ligation reactions. A series of ketone-bearing materials are built by tin (II)-mediated ring-opening polymerization followed by a postpolymerization deprotection step. The intended X-ray opacity is imparted through acid-catalyzed oxime postpolymerization modification of the resultant polymers with an iodinated hydroxylamine. All small molecules and polymeric materials are characterized using proton nuclear magnetic resonance (NMR) for purity, functional group stoichiometry, and number-averaged molecular weight calculations. Additionally, the polymers are evaluated with gel permeation chromatography (GPC) to determine polymer sample polydispersity and general molecular weight distribution shapes and by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) for thermal properties.