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 mm 2 . 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. M aterials capable of reversibly changing shape have the potential to enable simple mechanical devices, where traditional mechanical elements are difficult to employ. 1 Such materials are often categorized by the magnitude and complexity of achievable shape change in response to a given stimulus. Through patterning, it has been demonstrated that hydrogels, semicrystalline polymers, and liquid crystal networks can be designed to undergo complex shape change in response to solvents, light, and heat. 2−4 Complex shape change in monolithic materials is achieved through spatial and hierarchical control of the magnitude or direction of stimuli-response. In ordered materials this can be achieved through spatial control of molecular orientation.The polymerization of liquid crystalline monomers can retain the order within an elastic solid. 5 In uniaxially aligned liquid crystalline elastomers (LCEs), lightly cross-linked networks, reversible strains greater than 300% have been reported. 6 Oriented LCEs have typically been aligned by mechanical loading or magnetic fields, which can generate films with uniaxial or relatively simple patterns. 7,8 In densely cross-linked liquid crystal polymers, surface alignment techniques, such as rubbing or photoalignment, have been employed to prepare ordered polymer networks with comparatively complex local alignment. 9 Recently, main-chain LCEs that are amenable to photoalignment have been demonstrated, allowing for arbitrary spatial alignment of the nematic director over regions as small as 0.01 mm 2 . 10 Key to the realization of this material was the use of a two-step synthesis, comprised of the Michael addition of a nematic diacrylate to a primary amine followed by subsequent cross-linking of the telechelic diacrylate oligomer, which results in a LCE that exhibits maximum strains of 55%. 11 Critically, this reaction scheme can proceed in one-pot (a liquid crystal cell), exhibits a wide nematic phase window, and proceeds without the ad...

We report on electrically-induced, large magnitude (>300 nm), and reversible tuning of the selective reflection in polymer stabilized cholesteric liquid crystals (PSCLCs) prepared from negative dielectric anisotropy nematic liquid crystal hosts. The electrically-induced blue shift in the selective reflection of the PSCLCs is distinguished from our prior reports of bandwidth broadening and red-shifting tuning of the selective reflection in PSCLCs. The dominant factor in delineating the electro-optic response of the PSCLCs detailed here are the preparation conditions. Specifically, long exposure to UV intensity exceeding 250 mW cm. Other factors are shown to contribute to the response, including the type and concentration of photoinitiator.