Characterization of Photoinitiated Methacrylate based Covalent Adaptable Networks

• Riley Nick, Chemistry, University of Alabama at Birmingham

• Christopher Kloxin, Materials Science and Engineering and Chemical and Biomolecular Engineering, University of Delaware

Thermoset polymers are a common construction material due to their excellent mechanical properties and high temperature resistance; however, they are limited by being unable to be recycled and reprocessed. This study focuses on covalent adaptable networks (CANs) which are covalently crosslinked polymers that can undergo a bond exchange mechanism, which enables reprocessing after the formation of the polymer network. Based on previous research, methacrylate based CANs would be expected to exhibit stress relaxation at elevated temperatures. However, polymer networks prepared from Bisphenol A-glycidyl methacrylate (BisGMA) and 2-hydroxyethylmethacrylate (HEMA) exhibited a phenomenon of stress increase at elevated temperature. After further evaluation using thermal gravimetric analysis (TGA), it was concluded that the samples had 5 percent weight loss by 150°C  . It is proposed that the release of small molecules causes shrinkage, thus increasing stress within the network. Assessing thermal stability of polymer networks, and the potential for small molecule release, is a critical consideration for the preparation and determination of material composition of CANs. Future work will focus on modifying the network composition by utilizing materials less prone to producing small molecules at elevated temperatures, thus encouraging stress relaxation.