Research Progress

Modelling rheology of exchangeable liquid crystal elastomers

SourceColloquium Aug 15,2023
The coupling between the macroscopic shape change of the liquid crystal elastomer and the orientation of the microscopic mesogenic units in the elastomer makes it possible to perform mechanical work by adjusting the orientations of the mesogenic units. Meanwhile, monodomain liquid crystal elastomers with well-aligned mesogenic units have excellent mechanical properties, such as reversible large strain deformation, high strength and excellent toughness. However, due to the difficulty in achieving uniform alignment of mesogenic units due to random quenching and the non-recyclability of this material (similar to other common thermoset materials), liquid crystal elastomers have not been widely used in industry so far. To overcome the above difficulties, an exchangeable liquid crystal elastomer was successfully synthesized in 2014; unlike usual liquid crystal elastomers where the bond energy barrier is very high, making it difficult to re-arrange the cross-link bonds and the network structure, the bond-exchange reaction rate can be adjusted by adding catalyst and changing temperature in exchangeable liquid crystal elastomers. Although significant experimental progresses have been made in fabricating different exchangeable liquid crystal elastomers currently, a theoretical framework for understanding the physical properties of such exchangeable liquid crystal elastomers is still lacking, and the main difficulty in building this theory comes from the coupling between dynamic evolution of nematic order, entropic elasticity of polymer materials, energy dissipation caused by bond exchange reactions, etc.

Recently, Fanlong Meng 's research group at the Institute of Theoretical Physics, Chinese Academy of Sciences constructed a continuum theoretical model of exchangeable liquid crystal elastomers by considering micro-scaled bond exchange reactions, revealing the universal rheological properties that exchangeable liquid crystal elastomers may show in different application scenarios such as stress relaxation, strain ramp, creep compliance, etc. For further details, one can refer to the recent article:



Fan-Long Meng

Institute of Theoretical Physics, CAS