Exploring photo-deformation of polydomain liquid crystal polymers by homogenization

ABSTRACT

This article explores photo-deformation of polydomain liquid crystal polymers. Photo-isomerization-driven stimuli differ from thermal ones in mechanical response in that domains deform in differing amounts according to their relative alignment with respect to light polarization, by contracting along their liquid crystal orientation by an amount maximized at parallel alignment, and therefore polydomains’ response to light is complicated. Theoretical analysis of polydomain deformation with random domain alignments can be greatly simplified by applying homogenization method to obtain effective overall deformation. Not only is polydomain photo deformation very different from monodomain, but domain distributions enable very different photo responses. Anticlastic, syn-clastic and cylindrical-shell bending modes will be predicted, dictated by order parameter and material thickness. This work serves as a guide to theoretical analysis of composite materials with microstructure and to controlling their morphing shapes experimentally.

KEYWORDS:

• Liquid crystal
• polydomain
• homogenization
• photo-bend

Highlights

• LCE polydomain thin films deform rather differently under polarized light illuminations depending on whether their domain distribution is isotropic or transversely isotropic

• Isotropic polydomain thin films always contract along the light polarization and expand sideways by half, resulting in photo-induced anticlastic bends

• Transversely isotropic polydomain thin films can contract in plane and exhibit non-anticlastic bends under polarized light illuminations

Acknowledgements

The authors acknowledge the support of the National Science Foundation of China (Nos 11772094, 11461161008, 11272092). We thank Profs John S Biggins and Piotr Wasylczyk for suggestions.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [Nos 11772094, 11461161008, 11272092].