Compositional and Temperature Dependence of Amorphous Polymer Networks Undergoing Mechanotropic Phase Transitions

The deformation of liquid crystalline elastomers to load is nonlinear. Unlike traditional elastomeric thermosets, liquid crystalline elastomers can exhibit a slow recovery and considerable hysteresis. Recently, we reported the preparation of amorphous polymer networks that incorporate liquid crystalline monomer precursors. Upon deformation, these materials undergo mechanotropic phase transitions in which the initially amorphous state of the polymer network transitions into the nematic liquid crystalline phase. Perhaps unsurprisingly, the deformation of these materials is analogous to that of liquid crystalline elastomers. However, these materials distinctly recover the amorphous state rapidly with limited hysteresis. Here, we explore the contribution of the liquid crystalline monomer concentration and temperature on the deformation of amorphous polymer networks that exhibit mechanotropic phase transitions. This investigation elucidates the nature of the mechanically induced phase transition in these amorphous polymer networks and identifies that mechanotropic phase transitions are thermotropic.