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Programmable Liquid Crystal Elastomers Prepared by Thiol–Ene Photopolymerization

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journal contribution
posted on 15.09.2015, 00:00 by Taylor H. Ware, Zachary P. Perry, Claire M. Middleton, Scott T. Iacono, Timothy J. White
The spontaneous conversion of a flat film into a 3-D shape requires local programming of the mechanical response. Historically, the ability to locally program the mechanical response of high strain (>30%) liquid crystalline elastomers (LCEs) has been limited to magnetic or mechanical alignment techniques, which limits spatial resolution. Recently, we reported on the preparation of LCEs capable of 55% strain with spatial control of the mechanical response at scales as small as 0.01 mm2. Here, we report a distinct formulation strategy to realize programmable stimulus-response in LCEs. Photopolymerization of thiol–ene/acrylate formulations yields materials that exhibit large reversible strain up to 150%. The photopolymerization reaction is extremely rapid, reducing preparation time from days to minutes. The mechanical behavior of these materials can be tuned by varying cross-link density. Spatial and hierarchical programming of the director profile is demonstrated, enabling 3-D shape change, including twisting ribbons and localized Gaussian curvature.