BH-A is a rubbery solid at room temperature. To cast plates of the polymer for dynamic mechanical testing, the rubbery monomer was placed on a glass plate, bounded by silicone rubber. The glass plate was gradually heated to 80°C on a hot plate to allow the material transition into a viscous liquid and spread in the glass plate up to the boundary created by the silicone rubber. A second glass plate was used to form the casting cavity and the assembly was then clamped and placed into an OV301 precision composite curing vacuum oven (Easy composites). The resin was degassed at 110°C for 10 minutes, after which the vacuum was turned off and the temperature of the oven ramped to the cure temperature. The resin was cured at 170°C for 2 hours and post-cured at 190°C for 30 minutes.