Pure aliphatic polycarbonate networks via photoinduced anionic ring-opening polymerization at elevated temperature
Stephan Schandl, Thomas Koch, Jürgen Stampfl, Katharina Ehrmann, Robert Liska
Abstract
Aliphatic polycarbonates are highly regarded due to their potential as sustainable, biodegradable and inherently biocompatible materials. Therefore, much effort has been directed towards implementation of aliphatic polycarbonates into network structures. To date, these efforts have relied on incorporation of main- or sidechain functional groups into carbonate-containing monomers or oligomeric precursors, with pure polycarbonate networks remaining inaccessible. Here we show that recently developed thermally stable photobase generators have now made cyclic carbonates available for light-induced anionic ring-opening polymerization for the first time to form pure aliphatic polycarbonate networks at elevated temperatures. To gain insights into the polymerization mechanism, the reactivity of synthesized aromatically and aliphatically substituted cyclic carbonates was investigated utilizing photo-DSC and photorheology between 70 and 120 °C. A bifunctional cyclic carbonate was synthesized as crosslinker and tested for network formation with varying amounts of the monofunctional cyclic carbonate as reactive diluent. Tensile tests and DMTA measurements revealed tough, highly tunable (thermo-)mechanical properties of the obtained materials, depending on the ratio of reactive diluent to crosslinker.