Versatile Liquid Crystal Elastomer Formulations Using Amine-Acrylate Chemistry and Processing for Advanced Manufacturing

This
study aims to tune rheological properties of liquid
crystal
elastomers (LCEs) through a strategic approach, leveraging the differing
reaction rates of thiols and primary and secondary amines with acrylate
monomers or the inclusion of processing additives to enable amenability
to advanced manufacturing. We found that varying the time of oligomerization
at elevated temperatures of amine-functional monomers with acrylate-functional
monomers enabled simple control of rheological properties. Additionally,
we could also control rheological properties by introducing reinforcing
fillers or organic solvents. By varying the oligomerization conditions,
we achieved a broad range of viscosities, from 1.1 Pa s to 560 Pa
s as measured at 60 °C. When the rheological properties were
varied through the incorporation of various solid and liquid inclusions,
viscosities could range from less than 1 Pa s to nearly 1000 Pa s
when measured at 60 °C. The shape morphing capabilities that
are intrinsic to LCEs and the mechanical properties were also characterized.
We find that the oligomerization conditions and the addition of fillers
influence shape morphing and energy absorption, as characterized by
the stress–strain characteristics, further suggesting their
potential to be used in energy dissipation applications where performance
can be turned. Last, we demonstrate how the range of accessible rheological
properties grants formulations amenable to various advanced manufacturing
techniques.