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Lee M, Ha MY, Lee M, Kim JH, Kim SD, Kim I, Lee WB. Aligned structures of mesogenic motifs in epoxy resin and their thermal conductivities. NANOSCALE ADVANCES 2022; 4:1970-1978. [PMID: 36133416 PMCID: PMC9417641 DOI: 10.1039/d1na00896j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Accepted: 02/14/2022] [Indexed: 06/16/2023]
Abstract
The epoxy-based crosslinked polymer with the mesogenic group has been studied as a candidate resin material with high thermal conductivity due to the ordered structure of the mesogenic groups. In this study, we conducted all atomic molecular dynamics simulations with iterative crosslinking procedures on various epoxy resins with mesogenic motifs to investigate the effect of molecular alignment on thermal conductivity. The stacked structure of aromatic groups in the crosslinked polymer was analyzed based on the angle-dependent radial distribution function (ARDF), where the resins were categorized into three groups depending on their monomer shapes. The thermal conductivities of resins were higher than those of conventional polymers due to the alignment of aromatic groups, but no distinct correlation with the ARDF was found. Therefore, we conducted a further study about two structural factors that affect the alignment and the TC by comparing the resins within the same groups: the monomer with an alkyl spacer and functional groups in hardeners. The alkyl chains introduced in the epoxy monomers induced more stable stacking of aromatic groups, but thermal conductivity was lowered as they inhibited phonon transfer on the microscopic scale. In the other case, the functional groups in the hardener lowered the TC when the polar interaction with other polar groups in the monomer was strong enough to compete with the pi-pi interaction. These results represent how various chemical motifs in mesogenic groups affect their alignment on the atomistic scale, and also how they have effects on the TC consequently.
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Affiliation(s)
- Minhwan Lee
- School of Chemical and Biological Engineering, Seoul National University Seoul 08826 Republic of Korea
| | - Min Young Ha
- School of Chemical and Biological Engineering, Seoul National University Seoul 08826 Republic of Korea
| | - Mooho Lee
- Material Research Center, Samsung Advanced Institute of Technology, Samsung Electronics Co., Ltd Gyeonggi-do 16678 Republic of Korea
| | - Ju Hyun Kim
- Material Research Center, Samsung Advanced Institute of Technology, Samsung Electronics Co., Ltd Gyeonggi-do 16678 Republic of Korea
| | - Sung Dug Kim
- Material Research Center, Samsung Advanced Institute of Technology, Samsung Electronics Co., Ltd Gyeonggi-do 16678 Republic of Korea
| | - In Kim
- Material Research Center, Samsung Advanced Institute of Technology, Samsung Electronics Co., Ltd Gyeonggi-do 16678 Republic of Korea
| | - Won Bo Lee
- School of Chemical and Biological Engineering, Seoul National University Seoul 08826 Republic of Korea
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Soltani M, Raahemifar K, Nokhosteen A, Kashkooli FM, Zoudani EL. Numerical Methods in Studies of Liquid Crystal Elastomers. Polymers (Basel) 2021; 13:1650. [PMID: 34069440 PMCID: PMC8159147 DOI: 10.3390/polym13101650] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2021] [Revised: 04/19/2021] [Accepted: 04/21/2021] [Indexed: 01/24/2023] Open
Abstract
Liquid crystal elastomers (LCEs) are a type of material with specific features of polymers and of liquid crystals. They exhibit interesting behaviors, i.e., they are able to change their physical properties when met with external stimuli, including heat, light, electric, and magnetic fields. This behavior makes LCEs a suitable candidate for a variety of applications, including, but not limited to, artificial muscles, optical devices, microscopy and imaging systems, biosensor devices, and optimization of solar energy collectors. Due to the wide range of applicability, numerical models are needed not only to further our understanding of the underlining mechanics governing LCE behavior, but also to enable the predictive modeling of their behavior under different circumstances for different applications. Given that several mainstream methods are used for LCE modeling, viz. finite element method, Monte Carlo and molecular dynamics, and the growing interest and reliance on computer modeling for predicting the opto-mechanical behavior of complex structures in real world applications, there is a need to gain a better understanding regarding their strengths and weaknesses so that the best method can be utilized for the specific application at hand. Therefore, this investigation aims to not only to present a multitude of examples on numerical studies conducted on LCEs, but also attempts at offering a concise categorization of different methods based on the desired application to act as a guide for current and future research in this field.
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Affiliation(s)
- Madjid Soltani
- Department of Mechanical Engineering, K.N. Toosi University of Technology, Tehran 19991-43344, Iran; (F.M.K.); (E.L.Z.)
- Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada
- Centre for Biotechnology and Bioengineering (CBB), University of Waterloo, Waterloo, ON N2L 3G1, Canada
- School of Optometry and Vision Science, Faculty of Science, University of Waterloo, 200 University Ave. W, Waterloo, ON N2L 3G1, Canada;
- Advanced Bioengineering Initiative Center, Computational Medicine Center, K.N. Toosi University of Technology, Tehran 19991-43344, Iran
| | - Kaamran Raahemifar
- School of Optometry and Vision Science, Faculty of Science, University of Waterloo, 200 University Ave. W, Waterloo, ON N2L 3G1, Canada;
- College of Information Sciences and Technology (IST), Data Science and Artificial Intelligence Program, Penn State University, State College, Pennsylvania, PA 16801, USA
- Department of Chemical Engineering, Faculty of Engineering, University of Waterloo, 200 University Ave. W, Waterloo, ON N2L 3G1, Canada
| | - Arman Nokhosteen
- Department of Civil and Mechanical Engineering, University of Missouri-Kansas City, Kansas City, MO 64110, USA;
| | - Farshad Moradi Kashkooli
- Department of Mechanical Engineering, K.N. Toosi University of Technology, Tehran 19991-43344, Iran; (F.M.K.); (E.L.Z.)
| | - Elham L. Zoudani
- Department of Mechanical Engineering, K.N. Toosi University of Technology, Tehran 19991-43344, Iran; (F.M.K.); (E.L.Z.)
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Davidson EC, Kotikian A, Li S, Aizenberg J, Lewis JA. 3D Printable and Reconfigurable Liquid Crystal Elastomers with Light-Induced Shape Memory via Dynamic Bond Exchange. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e1905682. [PMID: 31664754 DOI: 10.1002/adma.201905682] [Citation(s) in RCA: 106] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2019] [Revised: 10/06/2019] [Indexed: 05/19/2023]
Abstract
3D printable and reconfigurable liquid crystal elastomers (LCEs) that reversibly shape-morph when cycled above and below their nematic-to-isotropic transition temperature (TNI ) are created, whose actuated shape can be locked-in via high-temperature UV exposure. By synthesizing LCE-based inks with light-triggerable dynamic bonds, printing can be harnessed to locally program their director alignment and UV light can be used to enable controlled network reconfiguration without requiring an imposed mechanical field. Using this integrated approach, 3D LCEs are constructed in both monolithic and heterogenous layouts that exhibit complex shape changes, and whose transformed shapes could be locked-in on demand.
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Affiliation(s)
- Emily C Davidson
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, MA, 02138, USA
| | - Arda Kotikian
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, MA, 02138, USA
| | - Shucong Li
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, 02138, USA
| | - Joanna Aizenberg
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, MA, 02138, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, 02138, USA
| | - Jennifer A Lewis
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, MA, 02138, USA
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Cresta V, Romano G, Kolpak A, Zalar B, Domenici V. Nanostructured Composites Based on Liquid-Crystalline Elastomers. Polymers (Basel) 2018; 10:E773. [PMID: 30960698 PMCID: PMC6403803 DOI: 10.3390/polym10070773] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Revised: 07/09/2018] [Accepted: 07/10/2018] [Indexed: 12/17/2022] Open
Abstract
Liquid-crystalline elastomers (LCEs) are the object of many research investigations due to their reversible and controllable shape deformations, and their high potential for use in the field of soft robots and artificial muscles. This review focuses on recent studies about polymer composites based on LCEs and nanomaterials having different chemistry and morphology, with the aim of instilling new physical properties into LCEs. The synthesis, physico-chemical characterization, actuation properties, and applications of LCE-based composites reported in the literature are reviewed. Several cases are discussed: (1) the addition of various carbon nanomaterials to LCEs, from carbon black to carbon nanotubes, to the recent attempts to include graphene layers to enhance the thermo-mechanic properties of LCEs; (2) the use of various types of nanoparticles, such as ferroelectric ceramics, gold nanoparticles, conductive molybdenum-oxide nanowires, and magnetic iron-oxide nanoparticles, to induce electro-actuation, magnetic-actuation, or photo-actuation into the LCE-based composites; (3) the deposition on LCE surfaces of thin layers of conductive materials (i.e., conductive polymers and gold nanolayers) to produce bending actuation by applying on/off voltage cycles or surface-wrinkling phenomena in view of tunable optical applications. Some future perspectives of this field of soft materials conclude the review.
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Affiliation(s)
- Vanessa Cresta
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa, via Moruzzi 13, 56124 Pisa, Italy.
| | - Giuseppe Romano
- Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139-4307, USA.
| | - Alexej Kolpak
- Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139-4307, USA.
| | - Boštjan Zalar
- Department of Condensed Matter Physics, Jozef Stefan Institute, Jamova Cesta 39, SI 1000 Ljubljana, Slovenia.
| | - Valentina Domenici
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa, via Moruzzi 13, 56124 Pisa, Italy.
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