1
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Terentjev EM. Liquid Crystal Elastomers: 30 Years After. Macromolecules 2025; 58:2792-2806. [PMID: 40160994 PMCID: PMC11948470 DOI: 10.1021/acs.macromol.4c01997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2024] [Revised: 02/19/2025] [Accepted: 02/25/2025] [Indexed: 04/02/2025]
Abstract
This is a Review that attempts to cast a look at the whole history of liquid crystal elastomers and the evolution of this field from its inception to the current state of the art. The exposition is limited by deliberately omitting several important elements of this field, such as densely cross-linked networks or smectic elastomers, focusing solely on the nematic phase of these elastomers. In this more narrow topic, we first discuss the current developments and perspectives in the materials chemistry. This is followed by three sections, each dedicated to one of the three main points of interest in the nematic liquid crystal elastomers: the reversible actuation, the soft elasticity, and the viscoelastic dynamics of nematic elastomers. In each of these directions, there have been significant developments over recent years but equally significant new avenues emerging for the research to follow.
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Affiliation(s)
- Eugene M. Terentjev
- Cavendish Laboratory, Cambridge
University, JJ Thomson
Avenue, Cambridge CB3 0HE, U.K.
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2
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Zhang F, Zhang J, Zhang K, Zhong X, He M, Qiu H, Gu J. Highly Thermally Conductive Liquid Crystalline Epoxy Resin Vitrimers with Reconfigurable, Shape-Memory, Photo-Thermal, and Closed-Loop Recycling Performance. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2025; 12:e2410362. [PMID: 39576734 PMCID: PMC11744650 DOI: 10.1002/advs.202410362] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2024] [Revised: 10/26/2024] [Indexed: 11/24/2024]
Abstract
The low thermal conductivity, poor toughness, and non-reprocessability of thermosetting epoxy resins severely restrict their applications and sustainable development in flexible electronics. Herein, liquid crystalline epoxy (LCE) and dynamic ester and disulfide bonds are introduced into the cured network of bisphenol A epoxy resin (E-51) to construct highly thermally conductive flexible liquid crystalline epoxy resin (LCER) vitrimers. LCER vitrimers demonstrate adjustable mechanical properties by varying the ratio of LCE to E-51, allowing it to transition from soft to strong. Typically, a 75 mol% LCE to 25 mol% E-51 ratio results in an in-plane thermal conductivity (λ) of 1.27 W m-1 K-1, over double that of pure E-51 vitrimer (0.61 W m-1 K-1). The tensile strength and toughness increase 2.88 folds to 14.1 MPa and 2.45 folds to 20.1 MJ m-3, respectively. Besides, liquid crystalline phase transition and dynamic covalent bonds enable triple shape memory and three-dimensional shape reconstruction. After four reprocessing cycles, λ and tensile strength remain at 94% and 72%, respectively. Integrating carbon nanotubes (CNTs) imparts photo-thermal effect and enables "on" and "off" switch under near-infrared light to LCER vitrimer. Furthermore, the CNTs/LCER vitrimer displays light-induced actuation, self-repairing, and self-welding besides the closed-loop recycling and rapid degradation performance.
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Affiliation(s)
- Fengyuan Zhang
- Shaanxi Key Laboratory of Macromolecular Science and TechnologySchool of Chemistry and Chemical EngineeringNorthwestern Polytechnical UniversityXi'anShaanxi710072P. R. China
| | - Junliang Zhang
- Shaanxi Key Laboratory of Macromolecular Science and TechnologySchool of Chemistry and Chemical EngineeringNorthwestern Polytechnical UniversityXi'anShaanxi710072P. R. China
| | - Kuan Zhang
- Shaanxi Key Laboratory of Macromolecular Science and TechnologySchool of Chemistry and Chemical EngineeringNorthwestern Polytechnical UniversityXi'anShaanxi710072P. R. China
| | - Xiao Zhong
- Shaanxi Key Laboratory of Macromolecular Science and TechnologySchool of Chemistry and Chemical EngineeringNorthwestern Polytechnical UniversityXi'anShaanxi710072P. R. China
| | - Mukun He
- Shaanxi Key Laboratory of Macromolecular Science and TechnologySchool of Chemistry and Chemical EngineeringNorthwestern Polytechnical UniversityXi'anShaanxi710072P. R. China
| | - Hua Qiu
- Shaanxi Key Laboratory of Macromolecular Science and TechnologySchool of Chemistry and Chemical EngineeringNorthwestern Polytechnical UniversityXi'anShaanxi710072P. R. China
| | - Junwei Gu
- Shaanxi Key Laboratory of Macromolecular Science and TechnologySchool of Chemistry and Chemical EngineeringNorthwestern Polytechnical UniversityXi'anShaanxi710072P. R. China
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3
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Zheng J, Feng H, Zhang X, Zheng J, Ng JKW, Wang S, Hadjichristidis N, Li Z. Advancing Recyclable Thermosets through C═C/C═N Dynamic Covalent Metathesis Chemistry. J Am Chem Soc 2024; 146:21612-21622. [PMID: 39046371 DOI: 10.1021/jacs.4c05346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/25/2024]
Abstract
Thermoset polymers have become integral to our daily lives due to their exceptional durability, making them feasible for a myriad of applications; however, this ubiquity also raises serious environmental concerns. Covalent adaptable networks (CANs) with dynamic covalent linkages that impart efficient reprocessability and recyclability to thermosets have garnered increasing attention. While various dynamic exchange reactions have been explored in CANs, many rely on the stimuli of active nucleophilic groups and/or catalysts, introducing performance instability and escalating the initial investment. Herein, we propose a new direct and catalyst-free C═C/C═N metathesis reaction between α-cyanocinnamate and aldimine as a novel dynamic covalent motif for constructing recyclable thermosets. This chemistry offers mild reaction conditions (room temperature and catalyst-free), ensuring high yields and simple isolation procedures. By incorporating dynamic C═C/C═N linkages into covalently cross-linked polymer networks, we obtained dynamic thermosets that exhibit both malleability and reconfigurability. The resulting tunable dynamic properties, coupled with the high thermal stability and recyclability of the C═C/C═N linkage-based networks, enrich the toolbox of dynamic covalent chemistry.
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Affiliation(s)
- Jie Zheng
- Institute of Sustainability for Chemicals, Energy and Environment (ISCE2), Agency for Science, Technology and Research (A*STAR), 1 Pesek Road, Jurong Island, Singapore 627833, Republic of Singapore
| | - Hongzhi Feng
- Institute of Sustainability for Chemicals, Energy and Environment (ISCE2), Agency for Science, Technology and Research (A*STAR), 1 Pesek Road, Jurong Island, Singapore 627833, Republic of Singapore
- Key Laboratory of Bio-Based Polymeric Materials Technology and Application of Zhejiang Province, Laboratory of Polymers and Composites, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, People's Republic of China
| | - Xinglong Zhang
- Institute of High Performance Computing (IHPC), Agency for Science, Technology, and Research (A*STAR), Singapore 138632, Republic of Singapore
| | - Jianwei Zheng
- Institute of High Performance Computing (IHPC), Agency for Science, Technology, and Research (A*STAR), Singapore 138632, Republic of Singapore
| | - Jeffrey Kang Wai Ng
- Institute of Sustainability for Chemicals, Energy and Environment (ISCE2), Agency for Science, Technology and Research (A*STAR), 1 Pesek Road, Jurong Island, Singapore 627833, Republic of Singapore
| | - Sheng Wang
- Institute of Sustainability for Chemicals, Energy and Environment (ISCE2), Agency for Science, Technology and Research (A*STAR), 1 Pesek Road, Jurong Island, Singapore 627833, Republic of Singapore
| | - Nikos Hadjichristidis
- Polymer Synthesis Laboratory, Chemistry Program, Physical Sciences and Engineering Division, KAUST Catalysis Center, King Abdullah University of Science and Technology (KAUST), Thuwal 23955, Saudi Arabia
| | - Zibiao Li
- Institute of Sustainability for Chemicals, Energy and Environment (ISCE2), Agency for Science, Technology and Research (A*STAR), 1 Pesek Road, Jurong Island, Singapore 627833, Republic of Singapore
- Institute of Materials Research and Engineering, Agency for Science, Technology, and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576, Republic of Singapore
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4
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Hu Z, Hu F, Deng L, Yang Y, Xie Q, Gao Z, Pan C, Jin Y, Tang J, Yu G, Zhang W. Reprocessible Triketoenamine-Based Vitrimers with Closed-Loop Recyclability. Angew Chem Int Ed Engl 2023; 62:e202306039. [PMID: 37314932 DOI: 10.1002/anie.202306039] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2023] [Revised: 06/11/2023] [Accepted: 06/14/2023] [Indexed: 06/16/2023]
Abstract
Development of thermosets that can be repeatedly recycled via both chemical route (closed-loop) and thermo-mechanical process is attractive and remains an imperative task. In this work, we reported a triketoenamine based dynamic covalent network derived from 2,4,6-triformylphloroglucinol and secondary amines. The resulting triketoenamine based network does not have intramolecular hydrogen bonds, thus reducing its π-electron delocalization, lowering the stability of the tautomer structure, and enabling its dynamic feature. By virtue of the highly reversible bond exchange, this novel dynamic covalent bond enables the easy construction of highly crosslinked and chemically reprocessable networks from commercially available monomers. The as-made polymer monoliths exhibit high mechanical properties (tensile strength of 79.4 MPa and Young's modulus of 571.4 MPa) and can undergo a monomer-network-monomer (yields up to 90 %) recycling mediated by an aqueous solution, with the new-generation polymer capable of restoring the material strength to its original state. In addition, owing to its dynamic nature, a catalyst-free and low-temperature reprogrammable covalent adaptable network (vitrimer) was achieved. The design concept reported herein can be applied to the development of other novel vitrimers with high repressibility and recyclability, and sheds light on future design of sustainable polymers with minimal environmental impact.
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Affiliation(s)
- Zeyou Hu
- College of Chemistry and Chemical Engineering, Hunan Key Laboratory of Micro & Nano Materials Interface Science, Central South University, Changsha, 410083, China
| | - Fan Hu
- College of Chemistry and Chemical Engineering, Hunan Key Laboratory of Micro & Nano Materials Interface Science, Central South University, Changsha, 410083, China
| | - Lifeng Deng
- College of Chemistry and Chemical Engineering, Hunan Key Laboratory of Micro & Nano Materials Interface Science, Central South University, Changsha, 410083, China
| | - Yumin Yang
- College of Chemistry and Chemical Engineering, Hunan Key Laboratory of Micro & Nano Materials Interface Science, Central South University, Changsha, 410083, China
| | - Qiujian Xie
- College of Chemistry and Chemical Engineering, Hunan Key Laboratory of Micro & Nano Materials Interface Science, Central South University, Changsha, 410083, China
| | - Zhu Gao
- College of Chemistry and Chemical Engineering, Hunan Key Laboratory of Micro & Nano Materials Interface Science, Central South University, Changsha, 410083, China
| | - Chunyue Pan
- College of Chemistry and Chemical Engineering, Hunan Key Laboratory of Micro & Nano Materials Interface Science, Central South University, Changsha, 410083, China
| | - Yinghua Jin
- Department of Chemistry, University of Colorado Boulder, Boulder, CO, 80309, USA
| | - Juntao Tang
- College of Chemistry and Chemical Engineering, Hunan Key Laboratory of Micro & Nano Materials Interface Science, Central South University, Changsha, 410083, China
| | - Guipeng Yu
- College of Chemistry and Chemical Engineering, Hunan Key Laboratory of Micro & Nano Materials Interface Science, Central South University, Changsha, 410083, China
| | - Wei Zhang
- Department of Chemistry, University of Colorado Boulder, Boulder, CO, 80309, USA
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5
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Zhao J, Meng F. Modeling Viscoelasticity and Dynamic Nematic Order of Exchangeable Liquid Crystal Elastomers. PHYSICAL REVIEW LETTERS 2023; 131:068101. [PMID: 37625059 DOI: 10.1103/physrevlett.131.068101] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2023] [Accepted: 04/26/2023] [Indexed: 08/27/2023]
Abstract
Exchangeable liquid crystal elastomers (XLCEs), an emerging class of recyclable polymer materials, consist of liquid crystalline polymers which are dynamically crosslinked. We develop a macroscopic continuum model by incorporating the microscopic dynamic features of the cross-links, which can be utilized to understand the viscoelasticity of the materials together with the dynamic nematic order. As applications of the model, we study the rheological responses of XLCEs in three cases: stress relaxation, strain ramp, and creep compliance, where the materials show interesting rheology as an interplay between the dynamic nematic order of the mesogenic units, the elasticity from the network structure, and the dissipation due to chain exchange reactions. Not only being useful in understanding the physical mechanism underlying the fascinating characteristics of XLCEs, this work can also guide their future fabrications with desired rheological properties.
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Affiliation(s)
- Jiameng Zhao
- CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Fanlong Meng
- CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
- Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou, Zhejiang 325000, China
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6
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Wang Z, Tang P, Chen S, Xing Y, Yin C, Feng J, Jiang F. Fully biobased sustainable elastomers derived from chitin, lignin, and plant oil via grafting strategy and Schiff-base chemistry. Carbohydr Polym 2023; 305:120577. [PMID: 36737210 DOI: 10.1016/j.carbpol.2023.120577] [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: 11/30/2022] [Revised: 01/05/2023] [Accepted: 01/09/2023] [Indexed: 01/12/2023]
Abstract
With the dramatically increased environmental problems, the rational design of sustainable polymers from renewable feedstocks opens new avenues to reduce the huge pollution impact. The major challenge for sustainable polymers is the decreased mechanical performance compared to that of petroleum-based materials. In this work, fully biobased sustainable elastomers were developed by integrating renewable chitin, lignin, and plant oil into one macromolecule, in which chitin was chosen as the rigid backbone, while a lignin-derived monomer vanillin acrylate (VA) and a plant oil-based monomer lauryl acrylate (LA) were selected as the hard and soft segments for the grafted side chains. A series of Chitin-graft-poly(vanillin acrylate-co-lauryl acrylate) (Chitin-g-P(VA-co-LA)) copolymers with varied feed ratios and chitin contents were synthesized by using reversible addition-fragmentation chain transfer (RAFT) polymerization as an effective grafting strategy. In addition, a dynamic cross-linked network was incorporated via Schiff-base reaction to improve the macroscopic behavior of such kind of chitin graft elastomers. These sustainable elastomers are mechanically strong and show excellent reprocessablity, as well as outstanding UV-blocking property. This strategy is versatile and can inspire the further development of fully biobased sustainable materials from natural resources.
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Affiliation(s)
- Zhiqiang Wang
- Biomass Molecular Engineering Center, Anhui Provincial Engineering Center for High Performance Biobased Nylons, Department of Materials Science and Engineering, School of Forestry and Landscape Architecture, Anhui Agricultural University, Hefei, Anhui 230036, China
| | - Pengfei Tang
- Biomass Molecular Engineering Center, Anhui Provincial Engineering Center for High Performance Biobased Nylons, Department of Materials Science and Engineering, School of Forestry and Landscape Architecture, Anhui Agricultural University, Hefei, Anhui 230036, China
| | - Shuaishuai Chen
- Biomass Molecular Engineering Center, Anhui Provincial Engineering Center for High Performance Biobased Nylons, Department of Materials Science and Engineering, School of Forestry and Landscape Architecture, Anhui Agricultural University, Hefei, Anhui 230036, China
| | - Yuxian Xing
- Biomass Molecular Engineering Center, Anhui Provincial Engineering Center for High Performance Biobased Nylons, Department of Materials Science and Engineering, School of Forestry and Landscape Architecture, Anhui Agricultural University, Hefei, Anhui 230036, China
| | - Chuantao Yin
- Biomass Molecular Engineering Center, Anhui Provincial Engineering Center for High Performance Biobased Nylons, Department of Materials Science and Engineering, School of Forestry and Landscape Architecture, Anhui Agricultural University, Hefei, Anhui 230036, China
| | - Jiajun Feng
- Biomass Molecular Engineering Center, Anhui Provincial Engineering Center for High Performance Biobased Nylons, Department of Materials Science and Engineering, School of Forestry and Landscape Architecture, Anhui Agricultural University, Hefei, Anhui 230036, China
| | - Feng Jiang
- Biomass Molecular Engineering Center, Anhui Provincial Engineering Center for High Performance Biobased Nylons, Department of Materials Science and Engineering, School of Forestry and Landscape Architecture, Anhui Agricultural University, Hefei, Anhui 230036, China.
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7
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Liang H, Wu Y, Zhang Y, Chen E, Wei Y, Ji Y. Elastomers Grow into Actuators. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2209853. [PMID: 36604968 DOI: 10.1002/adma.202209853] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 12/28/2022] [Indexed: 06/17/2023]
Abstract
It is common knowledge that when an elastomer (rubber) is stretched, its length will be maintained if its two ends are fixed. Here, it is serendipitously found that when an elastomer is slowly elongated further to achieve buckling under such conditions, the final length is much longer than the pre-stretched length. This allows the design of untethered autonomous synthetic-material-based soft robots that do not need any other chemical or electrical energy sources or external stimuli after the pre-strain is installed. Once the growth starts, the elongation continues to proceed even when the applied force is removed. Moreover, the elastomer, after growing, eventually forms a robust soft actuator that can be reshaped for different purposes. Few synthetic materials can grow like this, so far. This investigation shows that the material has an uncommon liquid crystal phase. Contrary to normal liquid crystals, it becomes birefringent only at high temperatures. The formation and the reshaping of the resulting soft actuators relate to a usually unnoticed reversible reaction. The work is promising to promote further understanding of dynamic covalent chemistry and liquid crystal elastomers, as well as to foster new designs and high-impact applications of bioinspired sustainable soft actuators in areas other than soft robots.
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Affiliation(s)
- Huan Liang
- The Key Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing, 100084, China
| | - Yahe Wu
- The Key Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing, 100084, China
| | - Yubai Zhang
- The Key Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing, 100084, China
| | - Erqiang Chen
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, Center for Soft Matter Science and Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Yen Wei
- The Key Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing, 100084, China
- Department of Chemistry, Center for Nanotechnology and Institute of Biomedical Technology, Chung-Yuan Christian University, Chung-Li, Taiwan, 32023, China
| | - Yan Ji
- The Key Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing, 100084, China
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8
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Guggenbiller G, Al Balushi A, Weems AC. Poly(β‐hydroxythioether)s as shape memory polymer foams for oil sorption in aquatic environments. J Appl Polym Sci 2022. [DOI: 10.1002/app.53569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Grant Guggenbiller
- Biomedical Engineering Program, Biomolecular and Chemical Engineering Department, Russ College of Engineering Ohio University Athens Ohio USA
| | - Ali Al Balushi
- Department of Mechanical Engineering, Russ College of Engineering Ohio University Athens Ohio USA
| | - Andrew C Weems
- Biomedical Engineering Program, Biomolecular and Chemical Engineering Department, Russ College of Engineering Ohio University Athens Ohio USA
- Department of Mechanical Engineering, Russ College of Engineering Ohio University Athens Ohio USA
- Ohio Musculoskeletal and Neurological Institute, and Center for Advanced Materials Processing, Russ College of Engineering Ohio University Athens Ohio USA
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9
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Fritz-Langhals E. Unique Superbase TBD (1,5,7-Triazabicyclo[4.4.0]dec-5-ene): From Catalytic Activity and One-Pot Synthesis to Broader Application in Industrial Chemistry. Org Process Res Dev 2022. [DOI: 10.1021/acs.oprd.2c00248] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Elke Fritz-Langhals
- Department of Chemistry, Technical University of Munich (TUM), Lichtenbergstraße 4, D-85747 Garching, Germany
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10
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Barnes M, Cetinkaya S, Ajnsztajn A, Verduzco R. Understanding the effect of liquid crystal content on the phase behavior and mechanical properties of liquid crystal elastomers. SOFT MATTER 2022; 18:5074-5081. [PMID: 35764591 DOI: 10.1039/d2sm00480a] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Liquid crystal elastomers are stimuli-responsive, shape-shifting materials. They typically require high temperatures for actuation which prohibits their use in many applications, such as biomedical devices. In this work, we demonstrate a simple and general approach to tune the order-to-disorder transition temperature (TODT) or nematic-to-isotropic transition temperature (TNI) of LCEs through variation of the overall liquid crystal mass content. We demonstrate reduction of the TNI in nematic LCEs through the incorporation of non-mesogenic linkers or the addition of lithium salts, and show that the TNI varies linearly with liquid crystal mass content over a broad range, approximately 50 °C. We also analyze data from prior reports that include three different mesogens, different network linking chemistries, and different alignment strategies, and show that the linear trend in TODT with liquid crystal mass content also holds for these systems. Finally, we demonstrate a simple approach to quantifying the maximum actuation strain through measurement of the soft elastic plateau and demonstrate applications of nematic LCEs with low TODTs, including the first body-responsive LCE that curls around a human finger due to body heat, and a fluidic channel that directionally pumps liquid when heated.
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Affiliation(s)
- Morgan Barnes
- Department of Materials Science and NanoEngineering, Rice University, Houston, Texas, 77005, USA.
| | - Sueda Cetinkaya
- Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas, 77005, USA
| | - Alec Ajnsztajn
- Department of Materials Science and NanoEngineering, Rice University, Houston, Texas, 77005, USA.
| | - Rafael Verduzco
- Department of Materials Science and NanoEngineering, Rice University, Houston, Texas, 77005, USA.
- Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas, 77005, USA
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11
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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: 13] [Impact Index Per Article: 4.3] [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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12
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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: 67] [Impact Index Per Article: 22.3] [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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13
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Liu Z, Xiong Y, Hao J, Zhang H, Cheng X, Wang H, Chen W, Zhou C. Liquid Crystal-Based Organosilicone Elastomers with Supreme Mechanical Adaptability. Polymers (Basel) 2022; 14:789. [PMID: 35215702 PMCID: PMC8880581 DOI: 10.3390/polym14040789] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 01/30/2022] [Accepted: 02/03/2022] [Indexed: 02/04/2023] Open
Abstract
Elastomers with supreme mechanical adaptability where the increasing stress under continuous deformation is significantly inhibited within a large deformation zone, are highly desired in many areas, such as artificial muscles, flexible and wearable electronics, and soft artificial-intelligence robots. Such system comprises the advantages of recoverable elasticity and internal compensation to external mechanical work. To obtain elastomer with supreme mechanical adaptability, a novel liquid crystal-based organosilicon elastomer (LCMQ) is developed in this work, which takes the advantages of reversible strain-induced phase transition of liquid crystal units in polymer matrix and the recoverable nano-sized fillers. The former is responsible for the inhibition of stress increasing during deformation, where the external work is mostly compensated by internal phase transition, and the latter provides tunable and sufficient high tensile strength. Such LCMQs were synthesized with 4-methoxyphenyl 4-(but-3-en-1-yloxy)benzoate (MBB) grafted thiol silicone oil (crosslinker-g-MBB) as crosslinking agent, vinyl terminated polydimethylsiloxane as base adhesive, and fumed silica as reinforcing filler by two-step thiol-ene "click" reaction. The obtained tensile strength and the elongation at break are better than previously reported values. Moreover, the resulting liquid crystal elastomers exhibit different mechanical behavior from conventional silicone rubbers. When the liquid crystal content increases from 1% (w/w) to 4% (w/w), the stress plateau for mechanical adaptability becomes clearer. Moreover, the liquid crystal elastomer has no obvious deformation from 25 °C to 120 °C and is expected to be used in industrial applications. It also provides a new template for the modification of organosilicon elastomers.
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Affiliation(s)
- Zhe Liu
- School of Materials Science and Engineering, Shandong University, Jinan 250061, China; (Z.L.); (J.H.); (H.Z.); (X.C.); (H.W.)
| | - Yuqi Xiong
- CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China, Hefei 230026, China;
| | - Jinghao Hao
- School of Materials Science and Engineering, Shandong University, Jinan 250061, China; (Z.L.); (J.H.); (H.Z.); (X.C.); (H.W.)
| | - Hao Zhang
- School of Materials Science and Engineering, Shandong University, Jinan 250061, China; (Z.L.); (J.H.); (H.Z.); (X.C.); (H.W.)
| | - Xiao Cheng
- School of Materials Science and Engineering, Shandong University, Jinan 250061, China; (Z.L.); (J.H.); (H.Z.); (X.C.); (H.W.)
| | - Hua Wang
- School of Materials Science and Engineering, Shandong University, Jinan 250061, China; (Z.L.); (J.H.); (H.Z.); (X.C.); (H.W.)
| | - Wei Chen
- CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China, Hefei 230026, China;
| | - Chuanjian Zhou
- School of Materials Science and Engineering, Shandong University, Jinan 250061, China; (Z.L.); (J.H.); (H.Z.); (X.C.); (H.W.)
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14
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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: 1.0] [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
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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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15
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Lin X, Gablier A, Terentjev EM. Imine-Based Reactive Mesogen and Its Corresponding Exchangeable Liquid Crystal Elastomer. Macromolecules 2022; 55:821-830. [PMID: 35572090 PMCID: PMC9098173 DOI: 10.1021/acs.macromol.1c02432] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Revised: 12/26/2021] [Indexed: 11/28/2022]
Abstract
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To date, exchangeable liquid crystalline
elastomers (xLCEs) have
been mainly fabricated by combining conventional LCEs with additional
exchangeable functional groups in their networks. While conventional
LCEs are frequently made from commercially available aromatic–ester
reacting mesogens or from mesogens based on a biphenyl core, such
reacting monomers are not optimized to fabricating xLCEs whose bond-exchange
reaction is fast and clean cut. Here, we develop a fast synthesis
route to produce a new type of reactive mesogen based on an aromatic–imine
structure that intrinsically enables a fast and stable bond-exchange
reaction in the resulting imine-based xLCE. This new xLCE displays
vitrimer plastic-flow behavior, and its bond-exchange activation energy
is calculated to be 54 kJ/mol. We also demonstrate that this xLCE
is thermally stable to withstand many recycling cycles without visible
decay, and its liquid crystallinity is preserved. Finally, we demonstrate
the reprogramming and realignment of the mesogen orientation in this
xLCE with the realigned xLCE capable of reversible thermal actuation.
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Affiliation(s)
- Xueyan Lin
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Alexandra Gablier
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Eugene M. Terentjev
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
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16
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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: 7] [Impact Index Per Article: 1.8] [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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17
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King O, Constant E, Weems AC. Shape Memory Poly(β-hydroxythioether) Foams for Oil Remediation in Aquatic Environments. ACS APPLIED MATERIALS & INTERFACES 2021; 13:20641-20652. [PMID: 33872493 DOI: 10.1021/acsami.1c02630] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Shape memory poly(β-hydroxythioether) foams were produced using organobase catalyzed reactions between epoxide and thiol monomers, allowing for the rapid formation of porous media within approximately 5 min, confirmed using both rheology and physical foam blowing. The porous materials possess ultralow densities (0.022 g × cm-3) and gel fractions of approximately 93%. Thermomechanical characterizations of the materials revealed glass transition temperatures tunable from approximately 50 to 100 °C, elastic moduli of approximately 2 kPa, and complete strain recovery upon heating of the sample above its glass transition temperature. The foams were characterized for their ability to take up oil from an aqueous multilayered ideal environment, revealing more than 2000% mass of oil (relative to the foam mass) could be collected. Importantly, while post-fabrication functionalization was possible with isocyanate chemistry followed by addition of hexadecanethiol or 3,3-bis(hexadecylthio)propan-1-ol, the oil collection efficiency of the system was not significantly enhanced, indicating that these materials, as porous media, possess unique attributes that make them appealing for environmental remediation without the need for costly modifications or manipulations.
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Affiliation(s)
- Olivia King
- Biomedical Engineering, Russ College of Engineering, Ohio University, Athens, Ohio 45701, United States
| | - Eric Constant
- Biomedical Engineering, Russ College of Engineering, Ohio University, Athens, Ohio 45701, United States
| | - Andrew C Weems
- Biomedical Engineering, Russ College of Engineering, Ohio University, Athens, Ohio 45701, United States
- Department of Mechanical Engineering; Translational Biosciences; Molecular and Chemical Biology; Orthopedic and Musculoskeletal Neurological Institute, Ohio University, Athens, Ohio 45701, United States
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