Fig. 2
From: High enthalpy storage thermoset network with giant stress and energy output in rubbery state
The enthalpy release during the free shape recovery process by DSC. a The DSC test results for the original SMP after synthesis. To avoid the post-curing effect and to match the thermal history with the programmed sample, the as prepared original SMP sample was heated at 170 °C for over 1 h before the DSC test. The typical glass transition curve, glass transition region, and glass transition temperature can be identified in the second heating cycle. b The DSC test results for the 40% compressive strain programmed sample. An inverse peak emerges during the first heating cycle in the pre-Tg region. The enthalpy release is confirmed by this first order transition. This is due to the retreat of stretched bonds formed during programming, which leads to release of the stored enthalpy, and the enthalpy release is ΔH = −2.85 J/g. The negative sign means the release of enthalpy. After release of the stored enthalpy, the second heating cycle also presents the classical second order glass transition curve. Based on the density of the sample, the specific enthalpy storage is 3.25 MJ/m3. Determination of the end points and baseline for calculating the enthalpy can be found in Supplementary Fig. 4
