815
Views
75
CrossRef citations to date
0
Altmetric
Invited Articles

Changing liquid crystal elastomer ordering with light – a route to opto-mechanically responsive materials

&
Pages 1263-1280 | Received 08 Apr 2009, Accepted 25 May 2009, Published online: 12 Oct 2009
 

Abstract

Long, flexible chains with rods and spacers give nematic polymer melts. Crosslinking yields highly extensible nematic elastomers. Molecular fluidity and orientational order are retained. Uniquely, these elastomers change shape drastically when orientational order is lost with temperature since chains lose their elongation. Reversible changes of 400% are easy to achieve. de Gennes envisaged this coupling between macroscopic strain and nematic (and other) liquid crystalline order.

Dye molecular rods are excited by photons into bent conformations. Bent rods depress orientational order and large thermal shape changes will be duplicated by light. Equally, rods may rotate away from the optical electric vector to avoid bending, thus also leading to mechanical strain. Mechanical recovery follows decay back to the molecular ground state. We sketch how these effects arise, explain how even polydomain networks deform under polarised and unpolarised light, and present new results on how nuclear magnetic resonance can reveal details of polydomain optical response. We explore non-linear absorption (photo-bleaching) leading to mechanical response where, by Beer's law, little light should theoretically penetrate.

In actuation, light penetrates quickly, is easy to deliver remotely, both excites and stimulates decay, and offers polarisation control over mechanics. Non-uniform director fields also control response. We illustrate novel photo-mechanical effects.

Acknowledgements

We thank E.M. Terentjev, P. Palffy-Muhoray, D. Broer, T.J. White and T. Ikeda for permission to reproduce figures, and B. Zalar for a critical reading of the review and for suggestions about NMR. This work was supported by EPSRC, UK.

Notes

1. Experimentally, it could perhaps be simpler to have the fixed field direction coincident with the propagation direction of the light.

Log in via your institution

Log in to Taylor & Francis Online

PDF download + Online access

  • 48 hours access to article PDF & online version
  • Article PDF can be downloaded
  • Article PDF can be printed
USD 61.00 Add to cart

* Local tax will be added as applicable

Related Research

People also read lists articles that other readers of this article have read.

Recommended articles lists articles that we recommend and is powered by our AI driven recommendation engine.

Cited by lists all citing articles based on Crossref citations.
Articles with the Crossref icon will open in a new tab.