1
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Herman JA, Hoang JD, White TJ. Elastocaloric Response of Isotropic Liquid Crystalline Elastomers. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2400786. [PMID: 38506590 DOI: 10.1002/smll.202400786] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Revised: 02/28/2024] [Indexed: 03/21/2024]
Abstract
Liquid crystalline elastomers (LCEs) are soft materials that associate order and deformation. Upon deformation, mechanically induced changes order affect entropy and can produce a caloric output (elastocaloric). Elastocaloric effects in materials continue to be considered for functional use as solid state refrigerants. Prior elastocaloric investigations of LCEs and related materials have measured ≈2 °C temperature changes upon deformation (100% strain). Here, the elastocaloric response of LCEs is explored that are prepared with a subambient nematic to isotropic transition temperature. These materials are referred as "isotropic" liquid crystalline elastomers. The LCEs are prepared by a two-step thiol-Michael/thiol-ene reaction. This polymer network chemistry enhances elastic recovery and reduces hysteresis compared to acrylate-based chemistries. The LCEs exhibit appreciable elastocaloric temperature changes upon deformation and recovery (> ± 3 °C, total ΔT of 6 °C) to deformation driven by minimal force (<< 1 MPa). Notably, the strong association of deformation and order and the resulting temperature change attained at low force achieves a responsivity of 14 °C MPa-1 which is seven times greater than natural rubber.
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Affiliation(s)
- Jeremy A Herman
- Department of Chemical and Biological Engineering, University of Colorado, Jennie Smoly Caruthers Biotechnology Building, 3415 Colorado Ave, Boulder, CO, 80303, USA
| | - Jonathan D Hoang
- Materials Science and Engineering Program, University of Colorado, Jennie Smoly Caruthers Biotechnology Building, 3415 Colorado Ave, Boulder, CO, 80303, USA
| | - Timothy J White
- Department of Chemical and Biological Engineering, University of Colorado, Jennie Smoly Caruthers Biotechnology Building, 3415 Colorado Ave, Boulder, CO, 80303, USA
- Materials Science and Engineering Program, University of Colorado, Jennie Smoly Caruthers Biotechnology Building, 3415 Colorado Ave, Boulder, CO, 80303, USA
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2
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Islam MS, Kedziora G, Lee J, Stafford A, Varshney V, Nepal D, Baldwin LA, Roy AK. Efficiency and Mechanism of Catalytic Siloxane Exchange in Vitrimer Polymers: Modeling and Density Functional Theory Investigations. J Phys Chem A 2024; 128:5627-5636. [PMID: 38957945 DOI: 10.1021/acs.jpca.4c01394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/04/2024]
Abstract
Of late, siloxane-containing vitrimers have gained significant interest due to their fast dynamic characteristics over a reasonable temperature range (180-220 °C), making them well-suited for diverse applications. The exchange reaction pathway in the siloxane vitrimers is accountable for the covalent adaptive network, with the reaction's effectiveness being regulated by either organic or organometallic catalysts. However, directly studying the exchange reaction pathway in the bulk phase using experimental approaches is challenging because of the intricate and interconnected structure of these vitrimers. Here, we perform comprehensive density functional theory (DFT) and experimental investigations to discover the detailed catalytic efficacy of siloxane exchange and provide direction for the reaction process using a 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) catalyst. The calculated transition barrier energy and catalytic efficiency of hexamethyldisiloxane and dihydroxy-dimethylsilane exchange derived from the nudged elastic band with transition-state calculations strongly agree with the experimental findings. In addition, Fukui indices, along with partial charges, are employed to evaluate the nucleophilic and electrophilic behaviors of silanol and siloxane molecules. Our analysis revealed that by utilizing the Fukui indices of both the acid and the base, we can make an approximate estimation of the respective kinetics of the SN2 process in the siloxane exchange reaction mechanism. These findings establish a foundation for comprehending a crucial aspect of the exchange mechanism in siloxane vitrimer systems and could aid in the development of novel catalysts.
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Affiliation(s)
- Md Sherajul Islam
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio 45433, United States
- Spectral Energies, LLC, Dayton, Ohio 45430, United States
| | - Gary Kedziora
- Inu Teq, LLC, NASA Ames Supercomputing Division, Moffet Field, Mountain View, California 94035, United States
- GDIT, AFRL/RC, Wright-Patterson Air Force Base, Dayton, Ohio 45433, United States
| | - Jonghoon Lee
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio 45433, United States
- ARCTOS Technology Solutions, Dayton, Ohio 45432, United States
| | - Alex Stafford
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio 45433, United States
| | - Vikas Varshney
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio 45433, United States
| | - Dhriti Nepal
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio 45433, United States
| | - Luke A Baldwin
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio 45433, United States
| | - Ajit K Roy
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio 45433, United States
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3
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Choi SH, Kim JH, Ahn J, Kim T, Jung Y, Won D, Bang J, Pyun KR, Jeong S, Kim H, Kim YG, Ko SH. Phase patterning of liquid crystal elastomers by laser-induced dynamic crosslinking. NATURE MATERIALS 2024; 23:834-843. [PMID: 38532072 DOI: 10.1038/s41563-024-01845-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Accepted: 02/21/2024] [Indexed: 03/28/2024]
Abstract
Liquid crystal elastomers hold promise in various fields due to their reversible transition of mechanical and optical properties across distinct phases. However, the lack of local phase patterning techniques and irreversible phase programming has hindered their broad implementation. Here we introduce laser-induced dynamic crosslinking, which leverages the precision and control offered by laser technology to achieve high-resolution multilevel patterning and transmittance modulation. Incorporation of allyl sulfide groups enables adaptive liquid crystal elastomers that can be reconfigured into desired phases or complex patterns. Laser-induced dynamic crosslinking is compatible with existing processing methods and allows the generation of thermo- and strain-responsive patterns that include isotropic, polydomain and monodomain phases within a single liquid crystal elastomer film. We show temporary information encryption at body temperature, expanding the functionality of liquid crystal elastomer devices in wearable applications.
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Affiliation(s)
- Seok Hwan Choi
- Department of Mechanical Engineering, Seoul National University, Seoul, Republic of Korea
| | - Ju Hee Kim
- Department of Chemical and Biological Engineering and Institute of Chemical Processes, Seoul National University, Seoul, Republic of Korea
| | - Jiyong Ahn
- Department of Mechanical Engineering, Seoul National University, Seoul, Republic of Korea
| | - Taegyeom Kim
- Department of Mechanical Engineering, Seoul National University, Seoul, Republic of Korea
| | - Yeongju Jung
- Department of Mechanical Engineering, Seoul National University, Seoul, Republic of Korea
| | - Daeyeon Won
- Department of Mechanical Engineering, Seoul National University, Seoul, Republic of Korea
| | - Junhyuk Bang
- Department of Mechanical Engineering, Seoul National University, Seoul, Republic of Korea
| | - Kyung Rok Pyun
- Department of Mechanical Engineering, Seoul National University, Seoul, Republic of Korea
| | - Seongmin Jeong
- Department of Mechanical Engineering, Seoul National University, Seoul, Republic of Korea
| | - Hyunsu Kim
- Department of Mechanical Engineering, Seoul National University, Seoul, Republic of Korea
| | - Young Gyu Kim
- Department of Chemical and Biological Engineering and Institute of Chemical Processes, Seoul National University, Seoul, Republic of Korea
| | - Seung Hwan Ko
- Department of Mechanical Engineering, Seoul National University, Seoul, Republic of Korea.
- Institute of Engineering Research / Institute of Advanced Machinery and Design (SNU-IAMD), Seoul National University, Seoul, Republic of Korea.
- Interdisciplinary Program in Bioengineering, Seoul National University, Seoul, Korea.
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4
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Wu H, Zhao C, Dai Y, Li K. Modeling of a light-fueled self-paddling boat with a liquid crystal elastomer-based motor. Phys Rev E 2024; 109:044705. [PMID: 38755847 DOI: 10.1103/physreve.109.044705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2023] [Accepted: 03/12/2024] [Indexed: 05/18/2024]
Abstract
Active materials possess unique properties of being able to respond autonomously to external stimuli, yet realizing and regulating the motion behavior of active machines remains a major challenge. Conventional control approaches, including sensor control and external device control, are both complex and difficult to implement. In contrast, active materials-based self-oscillators offer distinct properties such as periodic motion and ease of regulation. Inspired by paddle boats, we have proposed a conceptual light-fueled self-paddling boat with a photothermally responsive liquid crystal elastomer (LCE)-based motor that operates under steady illumination and incorporates an LCE fiber. Based on the well-established dynamic LCE model and rotation dynamics, the dynamic equations for governing the self-paddling of the LCE-steered boat are derived, and the driving torque of the LCE-based motor and the paddling velocity of the LCE-steered boat are formulated successively. The numerical results show that two motion modes of the boat under steady illumination: the static mode and the self-paddling mode. The self-paddling regime arises from the competition between the light-fueled driving torque and the frictional torque. Moreover, the critical conditions required to trigger the self-paddling are quantitatively examined as well as the significant system parameters affecting the driving torque, angular velocity, and paddling velocity. The proposed conceptual light-fueled self-paddling LCE-steered boat exhibits benefits including customizable size and being untethered and ambient powered, which provides valuable insights into the design and application of micromachines, soft robotics, energy harvesters, and beyond.
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Affiliation(s)
- Haiyang Wu
- School of Civil Engineering, Anhui Jianzhu University, Hefei, Anhui 230601, China
| | - Chongfeng Zhao
- School of Civil Engineering, Anhui Jianzhu University, Hefei, Anhui 230601, China
| | - Yuntong Dai
- School of Civil Engineering, Anhui Jianzhu University, Hefei, Anhui 230601, China
| | - Kai Li
- School of Civil Engineering, Anhui Jianzhu University, Hefei, Anhui 230601, China
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5
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Yu Y, Hu H, Dai Y, Li K. Modeling the light-powered self-rotation of a liquid crystal elastomer fiber-based engine. Phys Rev E 2024; 109:034701. [PMID: 38632774 DOI: 10.1103/physreve.109.034701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 02/08/2024] [Indexed: 04/19/2024]
Abstract
Self-oscillating systems possess the ability to convert ambient energy directly into mechanical work, and new types of self-oscillating systems are worth designing for practical applications in energy harvesters, engines and actuators. Taking inspiration from the four-stroke engine. A concept for a self-rotating engine is presented on the basis of photothermally responsive materials, consisting of a liquid crystal elastomer (LCE) fiber, a hinge and a turnplate, which can self-rotate under steady illumination. Based on the photo-thermal-mechanical model, a nonlinear theoretical model of the LCE-based engine under steady illumination is proposed to investigate its self-rotating behaviors. Numerical calculations reveal that the LCE-based engine experiences a supercritical Hopf bifurcation between the static regime and the self-rotation regime. The self-rotation of the LCE-based engine originates from the photothermally driven strain of the LCE fiber in illumination, and its continuous periodic motion is sustained by the correlation between photothermal energy and damping dissipation. The Hopf bifurcation conditions are also explored in detail, as well as the vital system parameters affecting self-rotation frequency. Compared to the abundant existing self-oscillating systems, this conceptual self-rotating LCE-based engine stands out due to its simple and lightweight structure, customizable dimensions and high speed, and it is expected to offer a broader range of design concepts applicable to soft robotics, energy harvesters, medical instruments, and so on.
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Affiliation(s)
- Yong Yu
- School of Civil Engineering, Anhui Jianzhu University, Hefei 230601, China
| | - Haoyu Hu
- School of Civil Engineering, Anhui Jianzhu University, Hefei 230601, China
| | - Yuntong Dai
- School of Civil Engineering, Anhui Jianzhu University, Hefei 230601, China
| | - Kai Li
- School of Civil Engineering, Anhui Jianzhu University, Hefei 230601, China
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6
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Bauman GE, White TJ. Rheology of oligomer melts in the nematic and isotropic states. SOFT MATTER 2023; 19:8882-8888. [PMID: 37955179 DOI: 10.1039/d3sm01084h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2023]
Abstract
Oligomers prepared by chain extension of liquid crystalline monomers are thermotropic. The alignment of liquid crystalline oligomers to shear flow via direct ink write printing is an increasingly popular approach to prepare aligned and 3-D printed liquid crystalline elastomers (LCEs). Here, we are concerned with the contribution of order and thermal history on the rheological properties of liquid crystalline. When the oligomers begin in a polydomain nematic state, the transition to an aligned nematic state occurs gradually over a wide range of shear rates. Conversely, when the oligomers begin in an isotropic state they behave as a Newtonian fluid until a critical shear rate is reached, at which point they align in a critical manner. It is shown that by either decreasing liquid crystalline content or increasing temperature, the viscosity of the oligomer melt decreases while this critical shear rate increases. In addition, the normal stress of oligomers is positive over all shear rates but decreases significantly in magnitude with increasing temperature. By combining the analysis of both temperature and liquid crystalline content, it is demonstrated that the temperature relative to the nematic-isotropic transition temperature is key to the oligomers' unique flow behaviors.
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Affiliation(s)
- Grant E Bauman
- Department of Chemical and Biological Engineering, University of Colorado Boulder, 596 UCB, Boulder, CO 80309, USA.
| | - Timothy J White
- Department of Chemical and Biological Engineering, University of Colorado Boulder, 596 UCB, Boulder, CO 80309, USA.
- Materials Science and Engineering Program, University of Colorado Boulder, 027 UCB, Boulder, CO 80303, USA
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7
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Chen G, Feng H, Zhou X, Gao F, Zhou K, Huang Y, Jin B, Xie T, Zhao Q. Programming actuation onset of a liquid crystalline elastomer via isomerization of network topology. Nat Commun 2023; 14:6822. [PMID: 37884494 PMCID: PMC10603074 DOI: 10.1038/s41467-023-42594-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Accepted: 10/16/2023] [Indexed: 10/28/2023] Open
Abstract
Tuning actuation temperatures of liquid crystalline elastomers (LCEs) achieves control of their actuation onsets, which is generally accomplished in the synthesis step and cannot be altered afterward. Multiple actuation onsets in one LCE can be encoded if the post-synthesis regulation of actuation temperature can be spatiotemporally achieved. This would allow realizing a logical time-evolution of actuation, desired for future soft robots. Nevertheless, this task is challenging given the additional need to ensure mesogen alignment required for actuation. We achieved this goal with a topology isomerizable network (TIN) of LCE containing aromatic and aliphatic esters in the mesogenic and amorphous phases, respectively. These two ester bonds can be distinctly activated for transesterification. The homolytic bond exchange between aliphatic esters allows mechanically induced mesogen alignment without affecting the mesogenic phase. Most importantly, the heterolytic exchange between aromatic and aliphatic esters changes the actuation temperature under different conditions. Spatial control of the two mechanisms via a photo-latent catalyst unleashes the freedom in regulating actuation temperature distribution, yielding unusual controllability in actuation geometries and logical sequence. Our principle is generally applicable to common LCEs containing both aromatic and aliphatic esters.
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Affiliation(s)
- Guancong Chen
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, Zhejiang, China
- College of Material, Chemistry and Chemical Engineering, Key Laboratory of Organosilicon Chemistry and Material Technology, Ministry of Education, Hangzhou Normal University, Hangzhou, 311121, Zhejiang, China
| | - Haijun Feng
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, Zhejiang, China
| | - Xiaorui Zhou
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, Zhejiang, China
| | - Feng Gao
- National Engineering Laboratory for Textile Fiber Materials & Processing Technology, Zhejiang Sci-Tech University, Hangzhou, 310018, Zhejiang, China
| | - Kai Zhou
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, Zhejiang, China
| | - Youju Huang
- College of Material, Chemistry and Chemical Engineering, Key Laboratory of Organosilicon Chemistry and Material Technology, Ministry of Education, Hangzhou Normal University, Hangzhou, 311121, Zhejiang, China
| | - Binjie Jin
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, Zhejiang, China.
| | - Tao Xie
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, Zhejiang, China
| | - Qian Zhao
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, Zhejiang, China.
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8
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Rehman HU, Hedenqvist MS, Chen Y, Guo Y, Li H, Liu H. Stretchable, Strong, Recyclable Helicide Elastomer Based on Dynamic Covalent Interactions. ACS APPLIED MATERIALS & INTERFACES 2023; 15:46280-46291. [PMID: 37729208 DOI: 10.1021/acsami.3c08329] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/22/2023]
Abstract
Current methods for making and disposing synthetic polymers have been widely pursued and are largely unsustainable. As a part of the solution, the reversible nature of dynamic covalent bonds emerges as an extraordinarily diverse and valuable feature in the development of exotic molecules and extended structures. With these bonds, it should be possible to construct recyclable and mechanically interlocked molecular structures using relatively simple precursors with preorganized geometries. A new helicide-based elastomer network is developed here with self-healing, recycling, and degradation features using a similar concept. The best self-healing performance (100%) was noted over 10-20 min, with various H2O, HCl, and NaOH solutions that delivered mechanical properties in the 1-1.4 MPa range. For hydrolytic degradation, the parameters are defined based on the type of binding, the pH of the solutions, and the copolymer network, which endowed a degradation time of approximately 4-11 h for each prepared sample. However, due to the reversible nature of the dynamic bonds, the material showed good recyclable mechanical properties compared to the pristine samples after five consecutive cycles, which meet the requirements of recyclable materials and recyclable packaging.
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Affiliation(s)
- Hafeez Ur Rehman
- State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
- Department of Physics, The University of Lahore, 1-KM Defense Road, Lahore 54000, Pakistan
| | - Mikael S Hedenqvist
- Department of Fibre and Polymer Technology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden
| | - Yujie Chen
- State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Yutong Guo
- State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Hua Li
- Collaborative Innovation Centre for Advanced Ship and Dee-Sea Exploration, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Hezhou Liu
- Collaborative Innovation Centre for Advanced Ship and Dee-Sea Exploration, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
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9
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Guo H, Saed MO, Terentjev EM. Mechanism of Pressure-Sensitive Adhesion in Nematic Elastomers. Macromolecules 2023; 56:6247-6255. [PMID: 37637306 PMCID: PMC10448750 DOI: 10.1021/acs.macromol.3c01038] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Revised: 06/25/2023] [Indexed: 08/29/2023]
Abstract
Nematic liquid crystal elastomers (LCEs) have anomalously high vibration damping, and it has been assumed that this is the cause of their anomalously high-pressure-sensitive adhesion (PSA). Here, we investigate the mechanism behind this enhanced PSA by first preparing thin adhesive tapes with LCE of varying cross-linking densities, characterizing their material and surface properties, and then studying the adhesion characteristics with a standard set of 90° peel, lap shear, and probe tack tests. The study confirms that the enhanced PSA is only present in (and due to) the nematic phase of the elastomer, and the strength of bonding takes over 24 h to fully reach its maximum value. Such a long saturation time is caused by the slow relaxation of local stress and director orientation in the nematic domains after pressing against the surface. We confirm this mechanism by showing that freshly pressed and annealed tape reaches the same maximum bonding strength on cooling, when the returning nematic order is forming in its optimal configuration in the pressed film.
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Affiliation(s)
- Hongye Guo
- Cavendish Laboratory, University
of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, U.K.
| | - Mohand O. Saed
- Cavendish Laboratory, University
of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, U.K.
| | - Eugene M. Terentjev
- Cavendish Laboratory, University
of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, U.K.
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10
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Bauman GE, Hoang JD, Toney MF, White TJ. Degree of Orientation in Liquid Crystalline Elastomers Defines the Magnitude and Rate of Actuation. ACS Macro Lett 2023; 12:248-254. [PMID: 36715430 DOI: 10.1021/acsmacrolett.2c00754] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The anisotropy of liquid crystalline elastomers (LCEs) is derived from the interaction-facilitated orientation of the molecular constituents. Here, we correlate the thermomechanical response of a series of LCEs subjected to mechanical alignment to measurements of the Hermans orientation parameter. The LCEs were systematically prepared with varying concentrations of liquid crystalline mesogens, which affects the relative degree of achievable order. These compositions were subject to varying degrees of mechanical alignment to prepare LCEs with orientations that span a wide range of orientation parameters. The stimuli-response of the LCEs indicates that the liquid crystalline content defines the temperature of actuation, whereas the orientation parameter of the LCE is intricately correlated to both the total actuation strain of the LCE as well as the rate of thermomechanical response.
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Affiliation(s)
- Grant E Bauman
- Department of Chemical and Biological Engineering, University of Colorado Boulder, 596 UCB, Boulder, Colorado 80309, United States
| | - Jonathan D Hoang
- Materials Science and Engineering Program, University of Colorado Boulder, 613 UCB, Boulder, Colorado 80303, United States
| | - Michael F Toney
- Department of Chemical and Biological Engineering, University of Colorado Boulder, 596 UCB, Boulder, Colorado 80309, United States.,Materials Science and Engineering Program, University of Colorado Boulder, 613 UCB, Boulder, Colorado 80303, United States.,Renewable and Sustainable Energy Institute, University of Colorado Boulder, 027 UCB, Boulder, Colorado 80309, United States
| | - Timothy J White
- Department of Chemical and Biological Engineering, University of Colorado Boulder, 596 UCB, Boulder, Colorado 80309, United States.,Materials Science and Engineering Program, University of Colorado Boulder, 613 UCB, Boulder, Colorado 80303, United States
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11
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Lewis KL, Herbert KM, Matavulj VM, Hoang JD, Ellison ET, Bauman GE, Herman JA, White TJ. Programming Orientation in Liquid Crystalline Elastomers Prepared with Intra-Mesogenic Supramolecular Bonds. ACS APPLIED MATERIALS & INTERFACES 2023; 15:3467-3475. [PMID: 36598490 DOI: 10.1021/acsami.2c18993] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
The large, directional stimuli-response of aligned liquid crystalline elastomers (LCEs) could enable functional utility in robotics, medicine, consumer goods, and photonics. The alignment of LCEs has historically been realized via mechanical alignment of a two-stage reaction. Recent reports widely utilize chain extension reactions of liquid crystal monomers (LCM) to form LCEs that are subject to either surface-enforced or mechanical alignment. Here, we prepare LCEs that contain intra-mesogenic supramolecular bonds synthesized via direct free-radical chain transfer photopolymerization processible by a distinctive mechanical alignment mechanism. The LCEs were prepared by the polymerization of a benzoic acid monomer (11OBA), which dimerized to form a liquid crystal monomer, with a diacrylate LCM (C6M). The incorporation of the intra-mesogenic hydrogen bonds increases the achievable nematic order from mechanical programming. Accordingly, LCEs prepared with larger 11OBA concentration exhibit higher magnitude thermomechanical strain values when compared to a LCE containing only covalent bonds. These LCEs can be reprogrammed with heat to return the aligned film to the polydomain state. The LCE can then be subsequently programmed to orient in a different direction. The facile preparation of (re)programmable LCEs with supramolecular bonds opens new avenues for the implementation of these materials as shape deployable elements.
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Affiliation(s)
- Kristin L Lewis
- Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, Colorado80309, United States
| | - Katie M Herbert
- Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, Colorado80309, United States
| | - Valentina M Matavulj
- Material Science and Engineering Program, University of Colorado Boulder, Boulder, Colorado80309, United States
| | - Jonathan D Hoang
- Material Science and Engineering Program, University of Colorado Boulder, Boulder, Colorado80309, United States
| | - Eric T Ellison
- Department of Geological Sciences, University of Colorado Boulder, Boulder, Colorado80309, United States
| | - Grant E Bauman
- Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, Colorado80309, United States
| | - Jeremy A Herman
- Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, Colorado80309, United States
| | - Timothy J White
- Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, Colorado80309, United States
- Material Science and Engineering Program, University of Colorado Boulder, Boulder, Colorado80309, United States
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12
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Goncharova IK, Kutumov SP, Novikov RA, Shiryaeva TY, Volodin AD, Korlyukov AA, Arzumanyan AV. The selective synthesis of di- and cyclosiloxanes bearing several hidden p-tolyl-functionalities. J Organomet Chem 2022. [DOI: 10.1016/j.jorganchem.2022.122482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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13
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Hebner TS, Kirkpatrick BE, Anseth KS, Bowman CN, White TJ. Surface-Enforced Alignment of Reprogrammable Liquid Crystalline Elastomers. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2204003. [PMID: 35988144 PMCID: PMC9561760 DOI: 10.1002/advs.202204003] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 08/04/2022] [Indexed: 05/31/2023]
Abstract
Liquid crystalline elastomers (LCEs) are stimuli-responsive materials capable of undergoing large deformations. The thermomechanical response of LCEs is attributable to the coupling of polymer network properties and disruption of order between liquid crystalline mesogens. Complex deformations have been realized in LCEs by either programming the nematic director via surface-enforced alignment or localized mechanical deformation in materials incorporating dynamic covalent chemistries. Here, the preparation of LCEs via thiol-Michael addition reaction is reported that are amenable to surface-enforced alignment. Afforded by the thiol-Michael addition reaction, dynamic covalent bonds are uniquely incorporated in chemistries subject to surface-enforce alignment. Accordingly, LCEs prepared with complex director profiles are able to be programmed and reprogrammed by (re)activating the dynamic covalent chemistry to realize distinctive shape transformations.
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Affiliation(s)
- Tayler S. Hebner
- Department of Chemical and Biological EngineeringUniversity of ColoradoBoulderCO80303USA
| | - Bruce E. Kirkpatrick
- Department of Chemical and Biological EngineeringUniversity of ColoradoBoulderCO80303USA
- Medical Scientist Training ProgramUniversity of Colorado Anschutz Medical CampusAuroraCO80045USA
| | - Kristi S. Anseth
- Department of Chemical and Biological EngineeringUniversity of ColoradoBoulderCO80303USA
- Materials Science and Engineering ProgramUniversity of ColoradoBoulderCO80303USA
| | - Christopher N. Bowman
- Department of Chemical and Biological EngineeringUniversity of ColoradoBoulderCO80303USA
- Materials Science and Engineering ProgramUniversity of ColoradoBoulderCO80303USA
| | - Timothy J. White
- Department of Chemical and Biological EngineeringUniversity of ColoradoBoulderCO80303USA
- Materials Science and Engineering ProgramUniversity of ColoradoBoulderCO80303USA
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14
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Debsharma T, Amfilochiou V, Wróblewska AA, De Baere I, Van Paepegem W, Du Prez FE. Fast Dynamic Siloxane Exchange Mechanism for Reshapable Vitrimer Composites. J Am Chem Soc 2022; 144:12280-12289. [PMID: 35758403 DOI: 10.1021/jacs.2c03518] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
To develop siloxane-containing vitrimers with fast dynamic characteristics, different mechanistic pathways have been investigated using a range of catalysts. In particular, one siloxane exchange pathway has been found to show a fast dynamic behavior in a useful temperature range (180-220 °C) for its application in vitrimers. The mechanism is found to involve 1,5,7-triazabicyclo [4.4.0] dec-5-ene (TBD) as an organic catalyst in the presence of hydroxyl groups. Using this new mechanistic approach, vitrimers with ultrafast stress-relaxation characteristics (relaxation times below 10 s) have been prepared with a readily available epoxy resin and siloxane-amine hardener. Subsequently, the low viscosity siloxane-containing vitrimer resin enabled the preparation of glass fiber-reinforced vitrimer composites using an industrially relevant vacuum-assisted resin infusion technique. The resulting composite was successfully thermoformed into a new shape, which makes it possible to envision a second life for such highly engineered materials.
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Affiliation(s)
- Tapas Debsharma
- Polymer Chemistry Research Group, Centre of Macromolecular Chemistry (CMaC), Department of Organic and Macromolecular Chemistry, Faculty of Sciences, Ghent University, Ghent B-9000, Belgium
| | - Virginia Amfilochiou
- Department of Materials, Textiles and Chemical Engineering, Mechanics of Materials and Structures, Ghent University, Technologiepark 46, Zwijnaarde 9052 , Belgium
| | - Aleksandra Alicja Wróblewska
- Polymer Chemistry Research Group, Centre of Macromolecular Chemistry (CMaC), Department of Organic and Macromolecular Chemistry, Faculty of Sciences, Ghent University, Ghent B-9000, Belgium
| | - Ives De Baere
- Department of Materials, Textiles and Chemical Engineering, Mechanics of Materials and Structures, Ghent University, Technologiepark 46, Zwijnaarde 9052 , Belgium
| | - Wim Van Paepegem
- Department of Materials, Textiles and Chemical Engineering, Mechanics of Materials and Structures, Ghent University, Technologiepark 46, Zwijnaarde 9052 , Belgium
| | - Filip E Du Prez
- Polymer Chemistry Research Group, Centre of Macromolecular Chemistry (CMaC), Department of Organic and Macromolecular Chemistry, Faculty of Sciences, Ghent University, Ghent B-9000, Belgium
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15
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Bauman GE, McCracken JM, White TJ. Actuation of Liquid Crystalline Elastomers at or Below Ambient Temperature. Angew Chem Int Ed Engl 2022; 61:e202202577. [PMID: 35482590 DOI: 10.1002/anie.202202577] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Indexed: 11/09/2022]
Abstract
Liquid crystal elastomers (LCE) are an emerging class of material actuators. LCE undergo macroscopic dimensional changes when subjected to a stimulus. The large stimuli-response of LCE is associated with thermotropic disruption of order. Historically, comparatively high temperatures are required to disrupt orientation in LCE to achieve meaningful work output. Here, we introduce an approach to prepare LCE via thiol-Michael/thiol-ene reactions that actuate at or below ambient temperature. Alignment was imparted to the LCE by mechanical alignment and 3D printing. The LCE materials detailed here achieve strains of 40 % with a maximum deformation rate of 6.5 % °C-1 . The functional utility of the tunability of the thermotropic response of these materials is illustrated in reconfiguration triggered via body heat and sequential actuation of a multi-material element.
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Affiliation(s)
- Grant E Bauman
- Department of Chemical and Biological Engineering, University of Colorado Boulder, 596 UCB, Boulder, CO 80309, USA
| | - Joselle M McCracken
- Department of Chemical and Biological Engineering, University of Colorado Boulder, 596 UCB, Boulder, CO 80309, USA
| | - Timothy J White
- Department of Chemical and Biological Engineering, University of Colorado Boulder, 596 UCB, Boulder, CO 80309, USA
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16
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Facile synthesis of amine-substituted cyclosiloxanes via a photocatalytic thiol-ene reaction to generate ketoenamine-linked hybrid networks. Polym J 2022. [DOI: 10.1038/s41428-022-00678-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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17
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Guo H, Saed MO, Terentjev EM. Thiol-acrylate side-chain liquid crystal elastomers. SOFT MATTER 2022; 18:4803-4809. [PMID: 35713099 PMCID: PMC9241586 DOI: 10.1039/d2sm00547f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 06/01/2022] [Indexed: 06/15/2023]
Abstract
The Michael addition 'click' chemistry was used to graft acrylate-terminated mesogenic groups onto the polysiloxane backbone polymer chain with thiol functional groups, with a constant 15% fraction of diacrylate reacting monomers as crosslinkers. Three different types of mesogens were used, and also their 50 : 50 mixtures, and in all cases we have obtained the smectic-A phase of the resulting liquid crystalline elastomer. Using X-ray diffraction, calorimetry and dynamic mechanical analysis, we investigated the relationship between the molecular structure of mesogenic side groups and the structure and properties of the elastomers. The shape-memory of smectic elastomers was verified. The unusual features were the semi-crystalline nature of elastomers with non-polar mesogens and the clear role of side-by-side rod dimerization of polar mesogens leading to a higher smectic layer spacing. We investigated the evolution of the smectic alignment on uniaxial stretching along the layer normal and identified two distinct ways in which the elastomer responds: the coarsened Helfrich-Hurault zig-zag layer texture and the large-scale stripe domains of uniform layer rotation in the systems with lower order parameter and the associated layer constraints.
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Affiliation(s)
- Hongye Guo
- Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 0HE, UK.
| | - Mohand O Saed
- Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 0HE, UK.
| | - Eugene M Terentjev
- Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 0HE, UK.
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18
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19
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Twisting for soft intelligent autonomous robot in unstructured environments. Proc Natl Acad Sci U S A 2022; 119:e2200265119. [PMID: 35605115 DOI: 10.1073/pnas.2200265119] [Citation(s) in RCA: 50] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
SignificanceAutonomy is crucial for soft robotics that are constructed of soft materials. It remains challenging to create autonomous soft robots that can intelligently interact with and adapt to changing environments without external controls. To do so, it often requires an analogical soft "brain" that integrates on-board sensing, control, computation, and decision-making. Here, we report an autonomous soft robot embodied with physical intelligence for decision-making via adaptive soft body-environment interactions and snap-through instability, without integrated sensing and external controls. This study harnesses physical intelligence as a new paradigm for designing autonomous soft robots that can interact intelligently with their environments, thus potentially reducing the burdens on the conventional integrated sensing, control, computations, and decision-making systems in designing intelligent soft robots.
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20
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Bauman GE, McCracken JM, White TJ. Actuation of Liquid Crystalline Elastomers at or Below Ambient Temperature. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202202577] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Grant E. Bauman
- Department of Chemical and Biological Engineering University of Colorado Boulder 596 UCB Boulder CO 80309 USA
| | - Joselle M. McCracken
- Department of Chemical and Biological Engineering University of Colorado Boulder 596 UCB Boulder CO 80309 USA
| | - Timothy J. White
- Department of Chemical and Biological Engineering University of Colorado Boulder 596 UCB Boulder CO 80309 USA
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21
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Li Y, Liu T, Ambrogi V, Rios O, Xia M, He W, Yang Z. Liquid Crystalline Elastomers Based on Click Chemistry. ACS APPLIED MATERIALS & INTERFACES 2022; 14:14842-14858. [PMID: 35319184 DOI: 10.1021/acsami.1c21096] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Liquid crystalline elastomers (LCEs) have emerged as an important class of functional materials that are suitable for a wide range of applications, such as sensors, actuators, and soft robotics. The unique properties of LCEs originate from the combination between liquid crystal and elastomeric network. The control of macroscopic liquid crystalline orientation and network structure is crucial to realizing the useful functionalities of LCEs. A variety of chemistries have been developed to fabricate LCEs, including hydrosilylation, free radical polymerization of acrylate, and polyaddition of epoxy and carboxylic acid. Over the past few years, the use of click chemistry has become a more robust and energy-efficient way to construct LCEs with desired structures. This article provides an overview of emerging LCEs based on click chemistries, including aza-Michael addition between amine and acrylate, radical-mediated thiol-ene and thiol-yne reactions, base-catalyzed thiol-acrylate and thiol-epoxy reactions, copper-catalyzed azide-alkyne cycloaddition, and Diels-Alder cycloaddition. The similarities and differences of these reactions are discussed, with particular attention focused on the strengths and limitations of each reaction for the preparation of LCEs with controlled structures and orientations. The compatibility of these reactions with the traditional and emerging processing techniques, such as surface alignment and additive manufacturing, are surveyed. Finally, the challenges and opportunities of using click chemistry for the design of LCEs with advanced functionalities and applications are discussed.
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Affiliation(s)
- Yuzhan Li
- School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
| | - Tuan Liu
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Veronica Ambrogi
- Department of Chemical, Materials and Production Engineering, University of Naples Federico II, Napoli 80125, Italy
| | - Orlando Rios
- Department of Materials Science and Engineering, The University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Min Xia
- School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China
| | - Wanli He
- School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
| | - Zhou Yang
- School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
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22
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Saed M, Gablier A, Terentjev EM. Exchangeable Liquid Crystalline Elastomers and Their Applications. Chem Rev 2022; 122:4927-4945. [PMID: 33596647 PMCID: PMC8915166 DOI: 10.1021/acs.chemrev.0c01057] [Citation(s) in RCA: 53] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Indexed: 12/30/2022]
Abstract
This Review presents and discusses the current state of the art in "exchangeable liquid crystalline elastomers", that is, LCE materials utilizing dynamically cross-linked networks capable of reprocessing, reprogramming, and recycling. The focus here is on the chemistry and the specific reaction mechanisms that enable the dynamic bond exchange, of which there is a variety. We compare and contrast these different chemical mechanisms and the key properties of their resulting elastomers. In the conclusion, we discuss the most promising applications that are enabled by dynamic cross-linking and present a summary table: a library of currently available materials and their main characteristics.
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Affiliation(s)
- Mohand
O. Saed
- Cavendish Laboratory, University
of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, U.K.
| | - Alexandra Gablier
- Cavendish Laboratory, University
of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, U.K.
| | - Eugene M. Terentjev
- Cavendish Laboratory, University
of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, U.K.
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23
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Hebner TS, Podgórski M, Mavila S, White TJ, Bowman CN. Shape Permanence in Diarylethene-Functionalized Liquid-Crystal Elastomers Facilitated by Thiol-Anhydride Dynamic Chemistry. Angew Chem Int Ed Engl 2022; 61:e202116522. [PMID: 35023253 DOI: 10.1002/anie.202116522] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Indexed: 11/07/2022]
Abstract
Diarylethene-functionalized liquid-crystalline elastomers (DAE-LCEs) containing thiol-anhydride bonds were prepared and shown to undergo reversible, reprogrammable photoinduced actuation. Upon exposure to UV light, a monodomain DAE-LCE generated 5.5 % strain. This photogenerated strain was demonstrated to be optically reversible over five cycles of alternating UV/Visible light exposure with minimal photochrome fatigue. The incorporation of thiol-anhydride dynamic bonds allowed for retention of actuated states. Further, re-programming of the nematic director was achieved by heating above the temperature for bond exchange to occur (70 °C) yet below the nematic-to-isotropic transition temperature (100 °C) such that order was maintained between mesogens. The observed thermal stability of each of the diarylethene isomers of over 72 h allowed for decoupling of photo-induced processes and polymer network effects, showing that both polymer relaxation and back-isomerization of the diarylethene contributed to LCE relaxation over a period of 12 hours after actuation unless bond exchange occurred.
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Affiliation(s)
- Tayler S Hebner
- Department of Chemical and Biological Engineering, University of Colorado Boulder, 596 UCB, Boulder, CO 80309, USA
| | - Maciej Podgórski
- Department of Chemical and Biological Engineering, University of Colorado Boulder, 596 UCB, Boulder, CO 80309, USA.,Department of Polymer Chemistry, Institute of Chemical Sciences, Faculty of Chemistry, Maria Curie-Sklowdowska University, M. Curie-Sklodowska Sq. 5, 20-031, Lublin, Poland
| | - Sudheendran Mavila
- Department of Chemical and Biological Engineering, University of Colorado Boulder, 596 UCB, Boulder, CO 80309, USA
| | - Timothy J White
- Department of Chemical and Biological Engineering, University of Colorado Boulder, 596 UCB, Boulder, CO 80309, USA.,Material Science and Engineering Program, University of Colorado Boulder, 596 UCB, Boulder, CO 80309, USA
| | - Christopher N Bowman
- Department of Chemical and Biological Engineering, University of Colorado Boulder, 596 UCB, Boulder, CO 80309, USA.,Material Science and Engineering Program, University of Colorado Boulder, 596 UCB, Boulder, CO 80309, USA
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24
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Park KW, Zujovic Z, Leitao EM. Synthesis and Characterization of Disiloxane Cross-Linked Polysulfides. Macromolecules 2022. [DOI: 10.1021/acs.macromol.1c02558] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Kun Woo Park
- School of Chemical Sciences, University of Auckland, Private Bag, 92019, Auckland 1142, New Zealand
- The MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington, Wellington 6140, New Zealand
| | - Zoran Zujovic
- School of Chemical Sciences, University of Auckland, Private Bag, 92019, Auckland 1142, New Zealand
| | - Erin M. Leitao
- School of Chemical Sciences, University of Auckland, Private Bag, 92019, Auckland 1142, New Zealand
- The MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington, Wellington 6140, New Zealand
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25
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Hong HJ, Park SY. Effects of network structure of main-chain liquid crystal elastomer on its thermal actuation performance. J IND ENG CHEM 2022. [DOI: 10.1016/j.jiec.2022.03.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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26
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Lin X, Zou W, Terentjev EM. Double Networks of Liquid-Crystalline Elastomers with Enhanced Mechanical Strength. Macromolecules 2022; 55:810-820. [PMID: 35572091 PMCID: PMC9097525 DOI: 10.1021/acs.macromol.1c02065] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2021] [Revised: 01/06/2022] [Indexed: 11/28/2022]
Abstract
![]()
Liquid-crystalline elastomers (LCEs)
are frequently used in soft
actuator development. However, applications are limited because LCEs
are prone to mechanical failure when subjected to heavy loads and
high temperatures during the working cycle. A mechanically tough LCE
system offers larger work capacity and lower failure rate for the
actuators. Herein, we adopt the double-network strategy, starting
with a siloxane-based exchangeable LCE and developing a series of
double-network liquid-crystalline elastomers (DN-LCEs) that are mechanically
tougher than the initial elastomer. We incorporate diacrylate reacting
monomers to fabricate DN-LCEs, some of which have the breaking stress
of 40 MPa. We incorporate thermoplastic polyurethane to fabricate
a DN-LCE, achieving an enormous ductility of 90 MJ/m3.
We have also attempted to utilize the aza-Michael chemistry to make
a DN-LCE that retains high plasticity because of several bond-exchange
mechanisms; however, it failed to produce a stable reprocessable LCE
system using conventional ester-based reactive mesogens. Each of these
DN-LCEs exhibits unique features and characteristics, which are compared
and discussed.
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Affiliation(s)
- Xueyan Lin
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, U.K
| | - Weike Zou
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, U.K
- State Key Laboratory of Chemical Engineering, Zhejiang University, Hangzhou 310027, P.R. China
| | - Eugene M. Terentjev
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, U.K
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27
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Cheng K, Chortos A, Lewis JA, Clarke DR. Photoswitchable Covalent Adaptive Networks Based on Thiol-Ene Elastomers. ACS APPLIED MATERIALS & INTERFACES 2022; 14:4552-4561. [PMID: 35006669 DOI: 10.1021/acsami.1c22287] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Covalent adaptive networks combine the advantages of cross-linked elastomers and dynamic bonding in a single system. In this work, we demonstrate a simple one-pot method to prepare thiol-ene elastomers that exhibit reversible photoinduced switching from an elastomeric gel to fluid state. This behavior can be generalized to thiol-ene cross-linked elastomers composed of different backbone chemistries (e.g., polydimethylsiloxane, polyethylene glycol, and polyurethane) and vinyl groups (e.g., allyl, vinyl ether, and acrylate). Photoswitching from the gel to fluid state occurs in seconds upon exposure to UV light and can be repeated over at least 180 cycles. These thiol-ene elastomers also exhibit the ability to heal, remold, and serve as reversible adhesives.
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Affiliation(s)
- Kezi Cheng
- School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Alex Chortos
- School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
- School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907, United States
| | - Jennifer A Lewis
- School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
| | - David R Clarke
- School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
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28
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Yang J, Gong J, Tao L, Tang Z, Yang Z, Cao P, Wang Q, Wang T, Luo H, Zhang Y. Reconfigurable and NIR-responsive shape memory polymer containing bipheunit units and graphene. Polym J 2022. [DOI: 10.1038/s41428-021-00609-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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29
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Ma J, Yang Y, Valenzuela C, Zhang X, Wang L, Feng W. Mechanochromic, Shape‐Programmable and Self‐Healable Cholesteric Liquid Crystal Elastomers Enabled by Dynamic Covalent Boronic Ester Bonds. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202116219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Jiazhe Ma
- School of Materials Science and Engineering Tianjin University Tianjin 300350
| | - Yanzhao Yang
- School of Materials Science and Engineering Tianjin University Tianjin 300350
| | - Cristian Valenzuela
- School of Materials Science and Engineering Tianjin University Tianjin 300350
| | - Xuan Zhang
- School of Materials Science and Engineering Tianjin University Tianjin 300350
| | - Ling Wang
- School of Materials Science and Engineering Tianjin University Tianjin 300350
| | - Wei Feng
- School of Materials Science and Engineering Tianjin University Tianjin 300350
- Tianjin Key Laboratory of Composite and Functional Materials Tianjin 300350 P. R. China
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30
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Hebner TS, Podgórski M, Mavila S, White TJ, Bowman CN. Shape Permanence in Diarylethene‐Functionalized Liquid Crystal Elastomers Facilitated by Thiol‐Anhydride Dynamic Chemistry. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202116522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Tayler S. Hebner
- University of Colorado Boulder Chemical and Biological Engineering 596 UCB 80309 Boulder UNITED STATES
| | - Maciej Podgórski
- University of Colorado Boulder Chemical and Biological Engineering UNITED STATES
| | - Sudheendran Mavila
- University of Colorado Boulder Chemical and Biological Engineering UNITED STATES
| | - Timothy J. White
- University of Colorado Boulder Chemical and Biological Engineering UNITED STATES
| | - Christopher N. Bowman
- University of Colorado Department of Chemical and Biological Engineering Campus Box 596, JSCBB Building 80309-0596 Boulder UNITED STATES
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31
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Zhang C, Lu X, Wang Z, Xia H. Progress in Utilizing Dynamic Bonds to Fabricate Structurally Adaptive Self-Healing, Shape Memory, and Liquid Crystal Polymers. Macromol Rapid Commun 2021; 43:e2100768. [PMID: 34964192 DOI: 10.1002/marc.202100768] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 12/15/2021] [Indexed: 11/09/2022]
Abstract
Stimuli-responsive structurally dynamic polymers are capable of mimicking the biological systems to adapt themselves to the surrounding environmental changes and subsequently exhibiting a wide range of responses ranging from self-healing to complex shape-morphing. Dynamic self-healing polymers (SHPs), shape-memory polymers (SMPs) and liquid crystal elastomers (LCEs), which are three representative examples of stimuli-responsive structurally dynamic polymers, have been attracting broad and growing interest in recent years because of their potential applications in the fields of electronic skin, sensors, soft robots, artificial muscles, and so on. We review recent advances and challenges in the developments towards dynamic SHPs, SMPs and LCEs, focusing on the chemistry strategies and the dynamic reaction mechanisms that enhance the performances of the materials including self-healing, reprocessing and reprogramming. We compare and discuss the different dynamic chemistries and their mechanisms on the enhanced functions of the materials, where three summary tables are presented: a library of dynamic bonds and the resulting characteristics of the materials. Finally, we provide a critical outline of the unresolved issues and future perspectives on the emerging developments. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Chun Zhang
- State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute, Sichuan University, Chengdu, 610065, China
| | - Xili Lu
- State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute, Sichuan University, Chengdu, 610065, China
| | - Zhanhua Wang
- State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute, Sichuan University, Chengdu, 610065, China
| | - Hesheng Xia
- State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute, Sichuan University, Chengdu, 610065, China
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32
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Ma J, Yang Y, Valenzuela C, Zhang X, Wang L, Feng W. Mechanochromic, Shape-Programmable and Self-Healable Cholesteric Liquid Crystal Elastomers Enabled by Dynamic Covalent Boronic Ester Bonds. Angew Chem Int Ed Engl 2021; 61:e202116219. [PMID: 34962037 DOI: 10.1002/anie.202116219] [Citation(s) in RCA: 68] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Indexed: 11/08/2022]
Abstract
Endowing a cholesteric liquid crystal elastomer (CLCE) exhibiting helicoidal nanostructure with dynamically tailorable functionalities is of paramount significance for its emerging applications in diverse fields such as adaptive optics and soft robotics. Here, a mechanochromic, shape-programmable and self-healable CLCE is judiciously designed and synthesized through integrating dynamic covalent boronic ester bonds into the main-chain CLCE polymer network. The circularly polarized reflection of CLCEs can be reversibly and dynamically tuned across the entire visible spectrum by mechanical stretching. Thanks to the introduction of dynamic boronic ester bonds, the CLCEs were found to show robust reprogrammable and self-healing capabilities. The research disclosed herein can provide new insights into the development of 4D (color and 3D shape) programmable photonic actuators towards bioinspired camouflage, adaptive optical systems, and next-generation intelligent machines.
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Affiliation(s)
- Jiazhe Ma
- Tianjin University, Materials Science & Engineering, CHINA
| | - Yanzhao Yang
- Tianjin University, Materials Science & Engineering, CHINA
| | | | - Xuan Zhang
- Tianjin University, Materials Science & Engineering, CHINA
| | - Ling Wang
- Tianjin University, Materials Science & Engineering, School of Materials Science and Engineering, Tianjin University, 300072, Tianjin, CHINA
| | - Wei Feng
- Tianjin University, Materials Science & Engineering, CHINA
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33
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Abstract
In contrast to conventional hard actuators, soft actuators offer many vivid advantages, such as improved flexibility, adaptability, and reconfigurability, which are intrinsic to living systems. These properties make them particularly promising for different applications, including soft electronics, surgery, drug delivery, artificial organs, or prosthesis. The additional degree of freedom for soft actuatoric devices can be provided through the use of intelligent materials, which are able to change their structure, macroscopic properties, and shape under the influence of external signals. The use of such intelligent materials allows a substantial reduction of a device's size, which enables a number of applications that cannot be realized by externally powered systems. This review aims to provide an overview of the properties of intelligent synthetic and living/natural materials used for the fabrication of soft robotic devices. We discuss basic physical/chemical properties of the main kinds of materials (elastomers, gels, shape memory polymers and gels, liquid crystalline elastomers, semicrystalline ferroelectric polymers, gels and hydrogels, other swelling polymers, materials with volume change during melting/crystallization, materials with tunable mechanical properties, and living and naturally derived materials), how they are related to actuation and soft robotic application, and effects of micro/macro structures on shape transformation, fabrication methods, and we highlight selected applications.
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Affiliation(s)
- Indra Apsite
- Faculty of Engineering Science, Department of Biofabrication, University of Bayreuth, Ludwig Thoma Str. 36A, 95447 Bayreuth, Germany
| | - Sahar Salehi
- Department of Biomaterials, Center of Energy Technology und Materials Science, University of Bayreuth, Prof.-Rüdiger-Bormann-Straße 1, 95447 Bayreuth, Germany
| | - Leonid Ionov
- Faculty of Engineering Science, Department of Biofabrication, University of Bayreuth, Ludwig Thoma Str. 36A, 95447 Bayreuth, Germany.,Bavarian Polymer Institute, University of Bayreuth, Universitätsstr. 30, 95440 Bayreuth, Germany
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Damoc M, Stoica AC, Dascalu M, Asandulesa M, Shova S, Cazacu M. Dual crystalline-amorphous salen-metal complexes behave like nematic droplets with AIEgens vistas. Dalton Trans 2021; 50:13841-13858. [PMID: 34522937 DOI: 10.1039/d1dt01980e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A series of metal salen complexes, original in view of the presence in their structure of a highly flexible and hydrophobic spacer, were prepared on the basis of the reaction of 1,3-bis(3-aminopropyl)tetramethyldisiloxane with 3,5-dichloro-, 3,5-dibromo- and 3-hydroxy-salicylaldehyde and various metal ions (Co2+, Ni2+, Cu2+ and Zn2+). The isolated products were completely characterized from the structural point of view by FTIR, NMR, elemental analysis and single crystal X-ray diffraction, and further investigated from the perspective of the behavior induced mainly by the structural peculiarities. Emphasis is placed on self-assembly properties, both in bulk and in solution, depending on temperature, solvent nature and concentration, including thermotropic and lyotropic liquid crystals (LC). LCs that appear in the form of nematic toroidal droplets have been fully demonstrated by polarized optical microscopy (POM), differential scanning calorimetry (DSC), broadband dielectric spectroscopy (BDS) and fluorescence anisotropy studies. The fluorescence analysis results revealed the aggregation-induced emission (AIE) phenomenon, where the emission occurs only for liquid crystals, with a few exceptions. Because these complexes can exist in both amorphous and crystalline states, it raised the question of how properties, such as electrical, change when switching from one state to another. These were well highlighted by DSC, BDS, PXRD, FTIR and fluorescence anisotropy.
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Affiliation(s)
- Madalin Damoc
- Department of Inorganic Polymers, "Petru Poni" Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41A, 700487 Iasi, Romania.
| | - Alexandru-Constantin Stoica
- Department of Inorganic Polymers, "Petru Poni" Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41A, 700487 Iasi, Romania.
| | - Mihaela Dascalu
- Department of Inorganic Polymers, "Petru Poni" Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41A, 700487 Iasi, Romania.
| | - Mihai Asandulesa
- Department of Inorganic Polymers, "Petru Poni" Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41A, 700487 Iasi, Romania.
| | - Sergiu Shova
- Department of Inorganic Polymers, "Petru Poni" Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41A, 700487 Iasi, Romania.
| | - Maria Cazacu
- Department of Inorganic Polymers, "Petru Poni" Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41A, 700487 Iasi, Romania.
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Bio-based vitrimer-like polyurethane based on dynamic imine bond with high-strength, reprocessability, rapid-degradability and antibacterial ability. POLYMER 2021. [DOI: 10.1016/j.polymer.2021.124208] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Sun D, Zhang J, Li H, Shi Z, Meng Q, Liu S, Chen J, Liu X. Toward Application of Liquid Crystalline Elastomer for Smart Robotics: State of the Art and Challenges. Polymers (Basel) 2021; 13:1889. [PMID: 34204168 PMCID: PMC8201031 DOI: 10.3390/polym13111889] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 05/29/2021] [Accepted: 05/31/2021] [Indexed: 11/17/2022] Open
Abstract
Liquid crystalline elastomers (LCEs) are lightly crosslinked polymers that combine liquid crystalline order and rubber elasticity. Owing to their unique anisotropic behavior and reversible shape responses to external stimulation (temperature, light, etc.), LCEs have emerged as preferred candidates for actuators, artificial muscles, sensors, smart robots, or other intelligent devices. Herein, we discuss the basic action, control mechanisms, phase transitions, and the structure-property correlation of LCEs; this review provides a comprehensive overview of LCEs for applications in actuators and other smart devices. Furthermore, the synthesis and processing of liquid crystal elastomer are briefly discussed, and the current challenges and future opportunities are prospected. With all recent progress pertaining to material design, sophisticated manipulation, and advanced applications presented, a vision for the application of LCEs in the next generation smart robots or automatic action systems is outlined.
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Affiliation(s)
- Dandan Sun
- School of Materials Science and Engineering, The Key Laboratory of Material Processing and Mold of Ministry of Education, Henan Key Laboratory of Advanced Nylon Materials and Application, Zhengzhou University, Zhengzhou 450001, China; (D.S.); (Z.S.); (Q.M.); (J.C.); (X.L.)
| | - Juzhong Zhang
- School of Materials Science and Engineering, The Key Laboratory of Material Processing and Mold of Ministry of Education, Henan Key Laboratory of Advanced Nylon Materials and Application, Zhengzhou University, Zhengzhou 450001, China; (D.S.); (Z.S.); (Q.M.); (J.C.); (X.L.)
| | - Hongpeng Li
- School of Mechanical Engineering, Yangzhou University, Yangzhou 225127, China;
| | - Zhengya Shi
- School of Materials Science and Engineering, The Key Laboratory of Material Processing and Mold of Ministry of Education, Henan Key Laboratory of Advanced Nylon Materials and Application, Zhengzhou University, Zhengzhou 450001, China; (D.S.); (Z.S.); (Q.M.); (J.C.); (X.L.)
| | - Qi Meng
- School of Materials Science and Engineering, The Key Laboratory of Material Processing and Mold of Ministry of Education, Henan Key Laboratory of Advanced Nylon Materials and Application, Zhengzhou University, Zhengzhou 450001, China; (D.S.); (Z.S.); (Q.M.); (J.C.); (X.L.)
| | - Shuiren Liu
- School of Materials Science and Engineering, The Key Laboratory of Material Processing and Mold of Ministry of Education, Henan Key Laboratory of Advanced Nylon Materials and Application, Zhengzhou University, Zhengzhou 450001, China; (D.S.); (Z.S.); (Q.M.); (J.C.); (X.L.)
| | - Jinzhou Chen
- School of Materials Science and Engineering, The Key Laboratory of Material Processing and Mold of Ministry of Education, Henan Key Laboratory of Advanced Nylon Materials and Application, Zhengzhou University, Zhengzhou 450001, China; (D.S.); (Z.S.); (Q.M.); (J.C.); (X.L.)
| | - Xuying Liu
- School of Materials Science and Engineering, The Key Laboratory of Material Processing and Mold of Ministry of Education, Henan Key Laboratory of Advanced Nylon Materials and Application, Zhengzhou University, Zhengzhou 450001, China; (D.S.); (Z.S.); (Q.M.); (J.C.); (X.L.)
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Lin X, Saed MO, Terentjev EM. Continuous spinning aligned liquid crystal elastomer fibers with a 3D printer setup. SOFT MATTER 2021; 17:5436-5443. [PMID: 33970980 PMCID: PMC8170681 DOI: 10.1039/d1sm00432h] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Accepted: 04/30/2021] [Indexed: 06/12/2023]
Abstract
Fibrous liquid crystalline elastomers (LCE) are an attractive variant of LCE-based actuators due to their small thickness, leading to faster response times to stimuli, as well as the increased mechanical strength. Fabrication of LCE fibers has been attempted by various research groups using electro-spinning or micro-fluidic techniques, without much success. Here we propose an alternative way to achieve single-step continuous spinning LCE fibers in a more scalable and robust way, based on a liquid-ink 3D printer. We demonstrate this technique in our home-made device by dynamically extruding/stretching liquid crystalline oligomer mixed with photo-reactive cross-linker, to fix the aligned network under UV light after extrusion. The report also describes a protocol for material synthesis and identifies optimal conditions for the stable fiber spinning process. Microns-thick LCE fibers with two different compositions have been successfully spun, and demonstrated enhanced mechanical properties with the inherited thermal-actuation capability. This technique also demonstrates the potential to fine-tune the mechanical properties of fibers to enable further development in fiber-based LCE applications.
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Affiliation(s)
- Xueyan Lin
- Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 0HE, UK.
| | - Mohand O Saed
- Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 0HE, UK.
| | - Eugene M Terentjev
- Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 0HE, UK.
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Wang Z, Cai S. Recent progress in dynamic covalent chemistries for liquid crystal elastomers. J Mater Chem B 2021; 8:6610-6623. [PMID: 32555841 DOI: 10.1039/d0tb00754d] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Liquid crystal elastomers (LCEs) have recently shown great potential in the applications of soft robotics, biomedical devices, active morphing structures, self-regulating systems and biomimetic demonstrations. Physical properties of LCEs highly depend on their crosslinking and the alignment of mesogens in the polymer network. Different strategies have been adopted to control and program the alignment of mesogens in LCEs over the recent decades, including stretching a loosely crosslinked LCE during its second-step crosslinking reaction, application of a strong magnetic or electrical field onto an LCE during its crosslinking process, and crosslinking a LCE thin film on the top of a surface with predesigned molecular texture. In the most recent decade, dynamic covalent bonds, which can undergo exchange reactions with or without external stimuli, have been introduced into LCEs to enable facile programing of mesogen orientation in the elastomer. In addition to the programmability, the LCEs with dynamic covalent bonds have also shown great recyclability, self-healing abilities and reprogrammability. In this article, we will review the recent progress in the synthesis, programming and application of LCEs with dynamic covalent bonds. We will also discuss the challenges and research opportunities in the field.
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Affiliation(s)
- Zhijian Wang
- Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, CA 92093, USA.
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40
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Gablier A, Saed MO, Terentjev EM. Transesterification in Epoxy–Thiol Exchangeable Liquid Crystalline Elastomers. Macromolecules 2020. [DOI: 10.1021/acs.macromol.0c01757] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Alexandra Gablier
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, U.K
| | - Mohand O. Saed
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, U.K
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Ohzono T, Norikane Y, Saed MO, Terentjev EM. Light-Driven Dynamic Adhesion on Photosensitized Nematic Liquid Crystalline Elastomers. ACS APPLIED MATERIALS & INTERFACES 2020; 12:31992-31997. [PMID: 32609481 DOI: 10.1021/acsami.0c08289] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In liquid crystal elastomers (LCEs), the internal mechanical loss increases around the nematic-isotropic phase transition and remains high all through the nematic phase, originating from the internal orientational relaxation related to the so-called "soft elasticity". Because the viscoelastic dissipation of the materials affects their adhesion properties, the nematic-isotropic phase transition can cause dramatic changes in the adhesion strength. Although the phase transitions can generally be induced by heat, here, we demonstrate the light-driven transition in dynamic adhesion in dye-doped nematic LCE. The special dye is chosen to efficiently generate local heat on light absorption. The adhesion strength is lowered with fine tunability depending on the light power, which governs the effective local temperature and through that the viscoelastic damping of the system. We demonstrate the light-assisted dynamic control of adhesion in a 90°-peel test and in pick-and-release of objects, which may lead to the development of stimuli-responsive adhesive systems with fine spatio-temporal controls.
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Affiliation(s)
- Takuya Ohzono
- Research Institute for Electronics and Photonics, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8565, Japan
| | - Yasuo Norikane
- Research Institute for Electronics and Photonics, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8565, Japan
| | - Mohand O Saed
- Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, U.K
| | - Eugene M Terentjev
- Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, U.K
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Saed MO, Terentjev EM. Catalytic Control of Plastic Flow in Siloxane-Based Liquid Crystalline Elastomer Networks. ACS Macro Lett 2020; 9:749-755. [PMID: 35648563 DOI: 10.1021/acsmacrolett.0c00265] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Liquid crystalline elastomer networks cross-linked by dynamic covalent bonds (xLCE) have the ability to be (re)processed during the plastic flow. However, the current bond-exchange strategies that are used to induce plastic flow in xLCE lack the efficient method to control the elastic-plastic transition. Here we describe a straightforward method to manipulate the transition to plastic flow via the choice of catalyst in xLCE cross-linked by siloxane. The nature and the amount of catalyst have a profound effect on the elastic-plastic transition temperature, and the stress relaxation behavior of the network. The temperature of fast plastic flow and the associated bond-exchange activation energy varied from 120 °C and 83 kJ/mol in the "fastest" exchange promoted by triazobicyclodecene (TBD) to 240 °C and 164 kJ/mol in the "slowest" exchange with triphenylphosphine (PPH), with a range of catalysts in between. We have identified the optimum conditions for programming an aligned monodomain xLCE, high programming temperature (230 °C) and low nematic to isotropic transition (60 °C), to achieve thermally and mechanically stable actuators.
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Affiliation(s)
- Mohand O. Saed
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Eugene M. Terentjev
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
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