Surface‐Enforced Alignment of Reprogrammable Liquid Crystalline Elastomers

Hebner, Tayler S.; Kirkpatrick, Bruce E.; Anseth, Kristi S.; Bowman, Christopher N.; White, Timothy J.

doi:10.1002/advs.202204003

Cited by 19 publications

(17 citation statements)

References 59 publications

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“…In LCEs formed by thiol-Michael reactions (LCE TM ), C6M was mixed with an aliphatic dithiol (HDT) in ratios of 0.25:1, 0.5:1, and 0.75:1 thiol/acrylate (by the reactive site). The thiol-Michael addition reaction was catalyzed by the addition of amines (triethylamine and diethylene triamine) . The monomer mixtures were filled into 30 μm alignment cells in the isotropic state and cooled to the nematic state to induce monodomain alignment.…”

Section: Resultsmentioning

confidence: 99%

“…A recent report details the preparation of LCEs via the thiol-Michael addition reaction that is compatible with alignment via surface anchoring. 21 Enabled by this report, this work prepares surface-aligned LCEs with these two synthetic approaches (Figure 1a) to elucidate the influence of these distinctive reactions on stimulus response and mechanical properties. Compositions were first subjected to either aza-Michael or thiol-Michael oligomerization (Figure 1b) to prepare acrylate-terminated oligomers which were subsequently crosslinked by photopolymerization.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Subsequent reports detailed the utilization of a similar approach, utilizing the thiol-Michael addition of diacrylate LCM, which initially was only amenable to mechanical alignment. A recent report details the preparation of LCEs via the thiol-Michael addition reaction that is compatible with alignment via surface anchoring . Enabled by this report, this work prepares surface-aligned LCEs with these two synthetic approaches (Figure a) to elucidate the influence of these distinctive reactions on stimulus response and mechanical properties.…”

Section: Resultsmentioning

confidence: 99%

“…Similar to the aza-Michael approach, thiol-Michael oligomerization has recently been shown to be amenable to surface alignment to allow the preparation of LCEs . In this reaction, dithiol monomers are mixed with excess liquid crystalline diacrylate monomers, and a catalyst is added to facilitate thiol-Michael addition .…”

Section: Introductionmentioning

confidence: 99%

“…7,20 Similar to the aza-Michael approach, thiol-Michael oligomerization has recently been shown to be amenable to surface alignment to allow the preparation of LCEs. 21 In this reaction, dithiol monomers are mixed with excess liquid crystalline diacrylate monomers, and a catalyst is added to facilitate thiol- Michael addition. 22 Again, the excess of acrylates is used to form acrylate-terminated oligomers that are photopolymerized once the thiol-Michael reaction is complete.…”

Section: ■ Introductionmentioning

confidence: 99%

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The Contribution of Oligomerization Reaction Chemistry to the Thermomechanical Properties of Surface-Aligned Liquid Crystalline Elastomers

et al. 2023

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Liquid crystalline elastomers (LCEs) are stimulus-responsive materials that, when macroscopically aligned, undergo large, directional deformation amplified by the disruption of order within a polymer network. Recently, surface-enforced alignment has been used to prepare LCEs with spatial variation in the director orientation that enables the realization of complex 3-D shape transformation. Surface-enforced alignment is advantageous because it allows for high-resolution, nonlinear patterning of the nematic director within an LCE. When using surface alignment to enforce orientation within LCEs, multiple two-step reaction schemes have been commonly used, primarily aza-Michael oligomerization or thiol-Michael oligomerization with each addition reaction followed by photopolymerization of the residual acrylate-terminated oligomers. Here, LCEs were prepared by each polymerization technique with varied amine or thiol concentrations. The mechanical properties, thermomechanical response, reaction kinetics, and alignment were characterized and assessed for LCEs. This examination emphasizes the importance of the molecular weight between crosslinks over the reaction used to form the oligomer in determining the magnitude of the stimulus response of LCEs.

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Section: Resultsmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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The Contribution of Oligomerization Reaction Chemistry to the Thermomechanical Properties of Surface-Aligned Liquid Crystalline Elastomers

et al. 2023

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Reprogrammable 4D Printed Liquid Crystal Elastomer Photoactuators by Means of Light‐Reversible Perylene Diimide Radicals

Montesino,

Martínez,

Sánchez‐Somolinos

2023

Adv Funct Materials

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Reconfigurable soft actuators can be programmed to morph into different 3D shapes under the same stimulus exhibiting great potential for adaptive robotic functionalities. Liquid crystalline crosslinked materials programmed and controlled by light have demonstrated great potential in this area, however, their implementation is mainly based on azobenzene chromophores, using ultraviolet light that can potentially damage the device and its surroundings, especially if living cells are present. Here, an ink is presented, containing a green‐absorbing perylene diimide chromophore, to prepare light active liquid crystalline elastomer (LCE) actuators via direct ink writing. Green light irradiation of the LCE elements leads to photothermal actuation, but also to new absorption bands in the far‐red and near‐infrared, ascribed to the formation of radical species. Far‐red irradiation results in mechanical actuation and, advantageously, a recovery of the original absorption spectrum. This reversible transformation enables spatial reconfigurability of the actuator's response to far‐red light. The reconfigurable system gives access to complex deformation modes by simply exciting the element with homogeneous far‐red light, without the need for any structural modification of the actuator. This material strategy, using green and far‐red light, less harmful than ultraviolet, shows significant promise for future development of reconfigurable actuators for biomedical applications.

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Facile Physicochemical Reprogramming of PEG‐Dithiolane Microgels

Nelson,

Kirkpatrick,

Skillin

et al. 2023

Adv Healthcare Materials

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Granular biomaterials have found widespread applications in tissue engineering, in part because of their inherent porosity, tunable properties, injectability, and 3D printability. However, the assembly of granular hydrogels typically relies on spherical microparticles and more complex particle geometries have been limited in scope, often requiring templating of individual microgels by microfluidics or in‐mold polymerization. Here, we use dithiolane‐functionalized synthetic macromolecules to fabricate photopolymerized microgels via batch emulsion, and then harness the dynamic disulfide crosslinks to rearrange the network. Through unconfined compression between parallel plates in the presence of photoinitiated radicals, we transform the isotropic microgels are transformed into disks. Characterizing this process, we find that the areas of the microgel surface in contact with the compressive plates are flattened while the curvature of the uncompressed microgel boundaries increases. When cultured with C2C12 myoblasts, cells localize to regions of higher curvature on the disk‐shaped microgel surfaces. This altered localization affects cell‐driven construction of large supraparticle scaffold assemblies, with spherical particles assembling without specific junction structure while disk microgels assemble preferentially on their curved surfaces. These results represent a unique spatiotemporal process for rapid reprocessing of microgels into anisotropic shapes, providing new opportunities to study shape‐driven mechanobiological cues during and after granular hydrogel assembly.

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Surface‐Enforced Alignment of Reprogrammable Liquid Crystalline Elastomers

Cited by 19 publications

References 59 publications

The Contribution of Oligomerization Reaction Chemistry to the Thermomechanical Properties of Surface-Aligned Liquid Crystalline Elastomers

The Contribution of Oligomerization Reaction Chemistry to the Thermomechanical Properties of Surface-Aligned Liquid Crystalline Elastomers

Reprogrammable 4D Printed Liquid Crystal Elastomer Photoactuators by Means of Light‐Reversible Perylene Diimide Radicals

Facile Physicochemical Reprogramming of PEG‐Dithiolane Microgels

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