Shape memory behaviors of 3D printed liquid crystal elastomers

Abstract

As soft active materials, shape-memory polymers (SMPs) and liquid crystal elastomers (LCEs) have attracted considerable research interest due to their potential applications in various areas. SMPs refer to polymeric materials that can return to their permanent shape in response to external stimuli, such as heat, light, and solvent. In this sense, LCEs can exhibit intrinsic shape-memory behaviors since LCEs can switch between two shapes with temperature change due to the order-disorder transition of liquid crystals. In this work, we fabricate both the polydomain and monodomain nematic LCEs through direct ink writing 3D printing. With increasing the temperature of the substrates, the printed LCEs change from the monodomain state to the polydomain state. For polydomain LCEs, a reversible shape change can occur upon constant loading, while the monodomain can switch the shape with temperature in the stress-free state. This two-way shape-memory behavior is caused by the nematic-isotropic phase transition. We further show that the printed LCEs exhibit a good one-way shape-memory effect due to glass transition. The shape recovery region increases with the programming temperature, which is a typical temperature memory effect. Finally, it is demonstrated that complex shape-memory performance can be designed by combining one-way and two-way shape-memory effects. Specifically, for the monodomain LCEs, with increasing temperature, the programmed shape first recovers, and a second shape change can further occur due to the nematic-isotropic transition.

Keywords

Liquid crystal elastomers / shape-memory polymers / two-way shape-memory effect / glass transition / nematic-isotropic transition / 3D printing

References

[1] Lendlein A.Reprogrammable recovery and actuation behaviour of shape-memory polymers.Nat Rev Mater2019;4:116-33

[2] Sun L,Ding Z.Stimulus-responsive shape memory materials: a review.Mater Des2012;33:577-640

[3] Lei M,Lu H.Recent progress in shape memory polymer composites: methods, properties, applications and prospects.Nanotechnol Rev2019;8:327-51

[4] Wang YJ,Hsu SH.Biodegradable water-based polyurethane shape memory elastomers for bone tissue engineering.ACS Biomater Sci Eng2018;4:1397-406

[5] Xue Y,Liu Z.A thermodynamic constitutive model for shape memory polymers based on phase transition.Polymer2022;243:124623

[6] Wang X,Gorbacheva G,Fu YQ.Multi-modal commutative dynamics in semi-crystalline polymers undergoing multiple shape memory behavior.Smart Mater Struct2021;30:045003

[7] Ramaraju H,Safranski DL.Designing biodegradable shape memory polymers for tissue repair.Adv Funct Mater2020;30:2002014

[8] Li Z,Wang Y,Lei M.3D printing of auxetic shape-memory metamaterial towards designable buckling.Int J Appl Mech2021;13:2150011

[9] Liu R,Luo X.Theoretical and numerical analysis of mechanical behaviors of a metamaterial-based shape memory polymer stent.Polymers2020;12:1784 PMCID:PMC7463968

[10] Zhang D,Xu P.World’s first application of a self-deployable mechanism based on shape memory polymer composites in Mars explorations: ground-based validation and on-Mars qualification.Smart Mater Struct2022;31:115008

[11] Xiao R.Heating/Solvent responsive shape-memory polymers for implant biomedical devices in minimally invasive surgery: current status and challenge.Macromol Biosci2020;20:e2000108

[12] Delaey J,Van Vlierberghe S.Shape-memory polymers for biomedical applications.Adv Funct Mater2020;30:1909047

[13] Salaris V,Lopez D,Peponi L.Shape-memory materials via electrospinning: a review.Polymers2022;14:995 PMCID:PMC8914658

[14] Zhang B,Cheng J.Mechanically robust and UV-curable shape-memory polymers for digital light processing based 4D printing.Adv Mater2021;33:e2101298

[15] Bastola AK.The shape - morphing performance of magnetoactive soft materials.Mater Des2021;211:110172

[16] Lin C,Li Y.4D-Printed biodegradable and remotely controllable shape memory occlusion devices.Adv Funct Mater2019;29:1906569

[17] Zhao D,Peng B.Corrosion fatigue behavior and anti-fatigue mechanisms of an additively manufactured biodegradable zinc-magnesium gyroid scaffold.Acta Biomater2022;153:614-29

[18] Sun S,Xie Y.Two-step heat treatment for laser powder bed fusion of a nickel-based superalloy with simultaneously enhanced tensile strength and ductility.Addit Manuf2021;46:102168

[19] Cai C,Shian TW.Laser powder bed fusion of Mo₂C/Ti-6Al-4V composites with alternately laminated α′/β phases for enhanced mechanical properties.Addit Manuf2021;46:102134

[20] Zhao D,Han C.3D printing of a titanium-tantalum Gyroid scaffold with superb elastic admissible strain, bioactivity and in-situ bone regeneration capability.Addit Manuf2021;47:102223

[21] Wang K,Zhu XX.Two-way reversible shape memory polymers made of cross-linked cocrystallizable random copolymers with tunable actuation temperatures.Macromolecules2017;50:8570-9

[22] Zare M,Parvin N.Thermally-induced two-way shape memory polymers: mechanisms, structures, and applications.Chem Eng J2019;374:706-20

[23] Chung T,Mather PT.Two-way reversible shape memory in a semicrystalline network.Macromolecules2008;41:184-92

[24] Behl M,Noechel U,Lendlein A.Temperature-memory polymer actuators.Proc Natl Acad Sci USA2013;110:12555-9

[25] Song H,Jin B,Zhao Q.Synergetic chemical and physical programming for reversible shape memory effect in a dynamic covalent network with two crystalline phases.ACS Macro Lett2019;8:682-6

[26] Wang Z,Zheng Y,Wang Y.Three-dimensional printing of functionally graded liquid crystal elastomer.Sci Adv2020;6: PMCID:PMC7518867

[27] Herbert KM,Mccracken JM,Koch JA.Synthesis and alignment of liquid crystalline elastomers.Nat Rev Mater2022;7:23-38

[28] Yakacki CM,Nair DP,Reed SM.Tailorable and programmable liquid-crystalline elastomers using a two-stage thiol-acrylate reaction.RSC Adv2015;5:18997-9001

[29] Wen Z,Raquez JM.A review on liquid crystal polymers in free-standing reversible shape memory materials.Molecules2020;25:1241 PMCID:PMC7179413

[30] Fuchi K,Buskohl PR.Topology optimization for the design of folding liquid crystal elastomer actuators.Soft Matter2015;11:7288-95

[31] Roach DJ,Kuang X.Long liquid crystal elastomer fibers with large reversible actuation strains for smart textiles and artificial muscles.ACS Appl Mater Interfaces2019;11:19514-21

[32] Wang Z,Cai S.Three-dimensional printing of liquid crystal elastomers and their applications.ACS Appl Polym Mater2022;4:3153-68

[33] Spillmann CM,Ratna BR,Selinger JV.Electrically induced twist in smectic liquid-crystalline elastomers.J Phys Chem B2016;120:6368-72

[34] Wang Z,Wang Y.Programmable actuation of liquid crystal elastomers via “living” exchange reaction.Soft Matter2019;15:2811-6

[35] Saed MO,Terentjev EM.Exchangeable liquid crystalline elastomers and their applications.Chem Rev2022;122:4927-45 PMCID:PMC8915166

[36] Peng X,Sun X.4D Printing of freestanding liquid crystal elastomers via hybrid additive manufacturing.Adv Mater2022;34:e2204890

[37] Traugutt NA,Luo C,Ge Q.Liquid-crystal-elastomer-based dissipative structures by digital light processing 3D printing.Adv Mater2020;32:e2000797

[38] Saed MO,Starr CA,Clark NA.Thiol-acrylate main-chain liquid-crystalline elastomers with tunable thermomechanical properties and actuation strain.J Polym Sci Part B Polym Phys2017;55:157-68

[39] Chen G,Shi Y,Shen Y.Rapidly and repeatedly reprogrammable liquid crystalline elastomer via a shape memory mechanism.Adv Mater2022;34:e2201679

[40] Javed M,Saed MO.Programmable shape change in semicrystalline liquid crystal elastomers.ACS Appl Mater Interfaces2022;14:35087-96

[41] Kotikian A,Boley JW,Lewis JA.3D printing of liquid crystal elastomeric actuators with spatially programed nematic order.Adv Mater2018;30:1706164

[42] Huang WM,Wang CC.Thermo/chemo-responsive shape memory effect in polymers: a sketch of working mechanisms, fundamentals and optimization.J Polym Res2012;19

[43] Linares CP, Traugutt NA, Saed MO, Martin Linares A, Yakacki CM, Nguyen TD. The effect of alignment on the rate-dependent behavior of a main-chain liquid crystal elastomer.Soft Matter2020;16:8782-98

[44] Chen SJ,Chen SG.Study on the structure and morphology of supramolecular shape memory polyurethane containing pyridine moieties.Smart Mater Struct2011;20:065003

[45] Yu K.Temperature memory effect in amorphous shape memory polymers.Soft Matter2014;10:9423-32