Photopatterning Crystal Orientation in Shape-Morphing Polymers

Jang, Lindy K.; Abdelrahman, Mustafa K.; Ware, Taylor H.

doi:10.1021/acsami.1c15630

Cited by 5 publications

(4 citation statements)

References 39 publications

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“…The normalized volume, as compared to the initial volume of each sample after cross-linking, for semicrystalline LCE at room temperature decreases from 1 to 0.87 ± 0.03 after the first heating and cooling cycle. The origin of this irreversible volume change is unclear, but it may be due to rearrangement of the crystalline fraction of the network. , In subsequent cycles, the normalized volume increases on heating from 0.87 ± 0.03 to 0.96 ± 0.06 at 250 °C. On cooling, the normalized volume returns to the value observed after the first heating and cooling cycle.…”

Section: Resultsmentioning

confidence: 99%

“…The origin of this irreversible volume change is unclear, but it may be due to rearrangement of the crystalline fraction of the network. 58,59 In subsequent cycles, the normalized volume increases on heating from 0.87 ± 0.03 to 0.96 ± 0.06 at 250 °C. On cooling, the normalized volume returns to the value observed after the first heating and cooling cycle.…”

Section: Resultsmentioning

confidence: 99%

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Programmable Shape Change in Semicrystalline Liquid Crystal Elastomers

Javed

Corazao

Saed

et al. 2022

ACS Appl. Mater. Interfaces

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Liquid crystal elastomers (LCEs) are stimuli-responsive materials capable of reversible and programmable shape change in response to an environmental stimulus. Despite the highly responsive nature of these materials, the modest elastic modulus and blocking stress exhibited by these actuating materials can be limiting in some engineering applications. Here, we engineer a semicrystalline LCE, where the incorporation of semicrystallinity in a lightly cross-linked liquid crystalline network yields tough and highly responsive materials. Directed self-assembly can be employed to program director profiles through the thickness of the semicrystalline LCE. In short, we use the alignment of a liquid crystal monomer phase to pattern the anisotropy of a semicrystalline polymer network. Both the semicrystalline-liquid crystalline and liquid crystalline−isotropic phase transition temperatures provide controllable shape transformations. A planarly aligned sample's normalized dimension parallel to the nematic director decreases from 1 at room temperature to 0.42 at 250 °C. The introduction of the semicrystalline nature also enhances the mechanical properties exhibited by the semicrystalline LCE. Semicrystalline LCEs have a storage modulus of 390 MPa at room temperature, and monodomain samples are capable of generating a contractile stress of 2.7 MPa on heating from 25 to 50 °C, far below the nematic to isotropic transition temperature. The robust mechanical properties of this material combined with the high actuation strain can be leveraged for applications such as soft robotics and actuators capable of doing significant work.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Programmable Shape Change in Semicrystalline Liquid Crystal Elastomers

Javed

Corazao

Saed

et al. 2022

ACS Appl. Mater. Interfaces

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“…Anisotropic wrinkling exploiting the anisotropic nature of LCP has been found to provide another alternative of physical self‐assembly to fabricate periodic microstructures. [ 170 , 171 , 172 , 173 ] LCP, which incorporates anisotropic mesogenic groups into polymer chains, is a polymer having liquid crystal (LC) state in molecular ordering, and it exhibits both high mobility and excellent anisotropic characteristics in the LC state. As a result of its anisotropic nature, it has been used in the microfabrication of oriented wrinkled surfaces.…”

Section: Fabricationmentioning

confidence: 99%

Wrinkled Interfaces: Taking Advantage of Anisotropic Wrinkling to Periodically Pattern Polymer Surfaces

et al. 2023

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Periodically patterned surfaces can cause special surface properties and are employed as functional building blocks in many devices, yet remaining challenges in fabrication. Advancements in fabricating structured polymer surfaces for obtaining periodic patterns are accomplished by adopting "top-down" strategies based on self-assembly or physico-chemical growth of atoms, molecules, or particles or "bottom-up" strategies ranging from traditional micromolding (embossing) or micro/nanoimprinting to novel laser-induced periodic surface structure, soft lithography, or direct laser interference patterning among others. Thus, technological advances directly promote higher resolution capabilities. Contrasted with the above techniques requiring highly sophisticated tools, surface instabilities taking advantage of the intrinsic properties of polymers induce surface wrinkling in order to fabricate periodically oriented wrinkled patterns. Such abundant and elaborate patterns are obtained as a result of self-organizing processes that are rather difficult if not impossible to fabricate through conventional patterning techniques. Focusing on oriented wrinkles, this review thoroughly describes the formation mechanisms and fabrication approaches for oriented wrinkles, as well as their fine-tuning in the wavelength, amplitude, and orientation control. Finally, the major applications in which oriented wrinkled interfaces are already in use or may be prospective in the near future are overviewed.

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“…21,22 The morphing of polymer materials oen requires prior stimulus activation of the switching units followed by subsequent mechanical loading to create deformation or temporary shapes. Typical documented switching units include reversible crystallization, 23 glass transition, 24 liquid crystal anisotropic/ isotropic transition, 25 supramolecular association, 12 dynamic covalent bonds, 26 and so forth. Considering that most potential applications of shape shiing polymers are as structural materials, direct application of mechanical force is an interesting trigger mechanism.…”

Section: Introductionmentioning

confidence: 99%