Circumventing physical limits of liquid crystalline elastomer actuation

Liquid crystalline elastomers (LCEs) are functional materials widely studied for their ability to produce large deformations. This deformation is a result of order disruption between mesogenic moieties incorporated in the polymer network. Often, reports detail that LCEs undergo an order-disorder transition analogous to low molar mass liquid crystalline systems.  However, in practice, LCEs deviate from this behavior. Prior investigation has associated the 2^nd order nature of the phase transition of LCEs to the retention of order in the crosslinks of the polymer network.

These physical limitations inspire and motivate our research, which has pursued theory-driven experimental study to enhance the stimuli-response.  In the preparation of LCE, we demonstrate the considerable influence of the orientational genesis (e.g., ordering of mesogens) during crosslinking in the LCEs. Theory suggests that the alignment method, which is associated with the phase conditions, will dramatically affect the stimuli-response. We examine this in developing a reaction chemistry amenable to both surface and stretch alignment, to prepare compositionally identical LCEs. As predicted by theory, the thermotropic response of LCEs is shifted by as much as 75°C between the two LCEs.  From this basis, we then detail that the thermotropic response of LCE can be further enhanced by reducing the strength of intermolecular interactions between mesogenic components in these LCEs.