Polymers move in response to light
Abstract
Abstract Significant advances have recently been made in the development of functional polymers that are able to undergo light‐induced shape changes. The main challenge in the development of such polymer systems is the conversion of photoinduced effects at the molecular level to macroscopic movement of working pieces. This article highlights some selected polymer architectures and their tailored functionalization processes. Examples include the contraction and bending of azobenzene‐containing liquid‐crystal elastomers and volume changes in gels. We focus especially on light‐induced shape‐memory polymers. These materials can be deformed and temporarily fixed in a new shape. They only recover their original, permanent shape when irradiated with light of appropriate wavelengths. Using light as a trigger for the shape‐memory effect will extend the applications of shape‐memory polymers, especially in the field of medical devices where triggers other than heat are highly desirable.
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Depending on the material, SMP stimuli can also be light, electricity, an alternating magnetic field, pH changes, and solvents.
“Depending on the material used, stimuli can also be light [27] (UV [28], infrared or laser light [29][30][31][32][33]), electricity [30,[34][35][36][37][38][39][40][41][42][43][44], an alternating magnetic field, pH changes [49] and solvents [50][51][52][53].”
From Review on the Functional Determinants and Durability of Shape Memory Polymers (2010) · cites this paper as [27]
Cites
Lendlein, A., Kelch, S., Kratz, K., Schulte, J., & Schauer, S. (2002) · Wiley eBooks · doi:10.1002/0471238961.1908011612051404.a01 · Cited by 2,616 · see citing works
Self-citationPhotoinduced Motions in Azo-Containing Polymers
Natansohn, A., & Rochon, P. (2002) · Chemical Reviews · doi:10.1021/cr970155y · Cited by 2,235 · see citing works
Directed bending of a polymer film by light
Yu, Y., Nakano, M., & Ikeda, T. (2003) · Nature · doi:10.1038/425145a · Cited by 2,177 · see citing works
Biodegradable, Elastic Shape-Memory Polymers for Potential Biomedical Applications
Lendlein, A., & Langer, R. (2002) · Science · doi:10.1126/science.1066102 · Cited by 2,146 · see citing works
Self-citationLight-induced shape-memory polymers
Lendlein, A., Jiang, H., Jünger, O., & Langer, R. (2005) · Nature · doi:10.1038/nature03496 · Cited by 2,006 · see citing works
Self-citationOptical Switching and Image Storage by Means of Azobenzene Liquid-Crystal Films
Ikeda, T., & Tsutsumi, O. (1995) · Science · doi:10.1126/science.268.5219.1873 · Cited by 1,549 · see citing works
Photoalignment of Liquid-Crystal Systems
Ichimura, K. (2000) · Chemical Reviews · doi:10.1021/cr980079e · Cited by 1,497 · see citing works
Light-Driven Motion of Liquids on a Photoresponsive Surface
Ichimura, K., Oh, S.-K., & Nakagawa, M. (2000) · Science · doi:10.1126/science.288.5471.1624 · Cited by 1,473 · see citing works
Linear and Nonlinear Optical Properties of Photochromic Molecules and Materials
Delaire, J. A., & Nakatani, K. (2000) · Chemical Reviews · doi:10.1021/cr980078m · Cited by 1,217 · see citing works
A New Opto-Mechanical Effect in Solids
Finkelmann, H., Nishikawa, E., Pereira, G. G., & Warner, M. (2001) · Physical Review Letters · doi:10.1103/physrevlett.87.015501 · Cited by 1,062 · see citing works
Phase transition in polymer gels induced by visible light
Suzuki, A., & Tanaka, T. (1990) · Nature · doi:10.1038/346345a0 · Cited by 1,035 · see citing works
Koerner, H., Price, G., Pearce, N. A., Alexander, M., & Vaia, R. A. (2004) · Nature Materials · doi:10.1038/nmat1059 · Cited by 1,034 · see citing works
Fast liquid-crystal elastomer swims into the dark
Camacho-Lopez, M. A., Finkelmann, H., Palffy‐Muhoray, P., & Shelley, M. (2004) · Nature Materials · doi:10.1038/nmat1118 · Cited by 1,009 · see citing works
Carbon black filled conducting polymers and polymer blends
Huang, J. (2002) · Advances in Polymer Technology · doi:10.1002/adv.10025 · Cited by 852 · see citing works
Ultrafast Dynamics of Photochromic Systems
Tamai, N., & Miyasaka, H. (2000) · Chemical Reviews · doi:10.1021/cr9800816 · Cited by 842 · see citing works
Photoinduced Plasticity in Cross-Linked Polymers
Scott, T. F., Schneider, A. D., Cook, W. D., & Bowman, C. N. (2005) · Science · doi:10.1126/science.1110505 · Cited by 779 · see citing works
Liquid crystal elastomers with mechanical properties of a muscle
Thomsen, D. L., Keller, P., Naciri, J., Pink, R., Jeon, H., Shenoy, D., & Ratna, B. R. (2001) · Macromolecules · doi:10.1021/ma001639q · Cited by 689 · see citing works
Behl, M., & Lendlein, A. (2011) · Wiley eBooks · doi:10.1002/0471238961.1908011612051404.a01.pub2 · Cited by 664 · see citing works
Self-citationAnisotropic Bending and Unbending Behavior of Azobenzene Liquid‐Crystalline Gels by Light Exposure
Ikeda, T., Nakano, M., Yu, Y., Tsutsumi, O., & Kanazawa, A. (2003) · Advanced Materials · doi:10.1002/adma.200390045 · Cited by 594 · see citing works
Light‐Driven Side‐On Nematic Elastomer Actuators
Li, M., Keller, P., Li, B., Wang, X., & Brunet, M. (2003) · Advanced Materials · doi:10.1002/adma.200304552 · Cited by 591 · see citing works
Shape-memory materials and hybrid composites for smart systems: Part I Shape-memory materials
Wei, Z., Sandstroröm, R., & Miyazaki, S. (1998) · Journal of Materials Science · doi:10.1023/a:1004692329247 · Cited by 582 · see citing works
Transdermal photopolymerization for minimally invasive implantation
Elisseeff, J. H., Anseth, K. S., Sims, D. C., McIntosh, W., Randolph, M. A., & Langer, R. (1999) · Proceedings of the National Academy of Sciences · doi:10.1073/pnas.96.6.3104 · Cited by 576 · see citing works
Shibaev, V. P., Bobrovsky, A. Y., & Boiko, N. I. (2003) · Progress in Polymer Science · doi:10.1016/s0079-6700(02)00086-2 · Cited by 425 · see citing works
Photomechanical actuation in polymer–nanotube composites
Ahir, S. V., & Terentjev, E. M. (2005) · Nature Materials · doi:10.1038/nmat1391 · Cited by 423 · see citing works
Photoinduced phase transition of gels
Mamada, A., Tanaka, T., Kungwatchakun, D., et al. (1990) · Macromolecules · doi:10.1021/ma00207a046 · Cited by 378 · see citing works
uv manipulation of order and macroscopic shape in nematic elastomers
Hogan, P. M., Tajbakhsh, A. R., & Terentjev, E. M. (2002) · Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics · doi:10.1103/physreve.65.041720 · Cited by 366 · see citing works
Reversible phase transitions in polymer gels induced by radiation forces
Juodkazis, S., Mukai, N., Wakaki, R., Yamaguchi, A., Matsuo, S., & Misawa, H. (2000) · Nature · doi:10.1038/35041522 · Cited by 346 · see citing works
Photothermal properties of shape memory polymer micro‐actuators for treating stroke*
Maitland, D. J., Metzger, M. F., Schumann, D., Lee, A., & Wilson, T. S. (2002) · Lasers in Surgery and Medicine · doi:10.1002/lsm.10007 · Cited by 332 · see citing works
Shape Memory Effect Exhibited by Smectic-C Liquid Crystalline Elastomers
Rousseau, I. A., & Mather, P. T. (2003) · Journal of the American Chemical Society · doi:10.1021/ja039001s · Cited by 290 · see citing works
The generic enhancement of photochromic dye switching speeds in a rigid polymer matrix
Evans, R. A., Hanley, T. L., Skidmore, M. A., et al. (2005) · Nature Materials · doi:10.1038/nmat1326 · Cited by 239 · see citing works
Irie, M., & Kunwatchakun, D. (1986) · Macromolecules · doi:10.1021/ma00164a003 · Cited by 234 · see citing works
Yu, Y., Nakano, M., Shishido, A., Shiono, T., & Ikeda, T. (2004) · Chemistry of Materials · doi:10.1021/cm035092g · Cited by 226 · see citing works
Eisenbach, C. D. (1980) · Polymer · doi:10.1016/0032-3861(80)90083-x · Cited by 219 · see citing works
Irie, M. (2006) · Springer eBooks · doi:10.1007/bfb0043060 · Cited by 179 · see citing works
Light-induced tailoring of PEG-hydrogel properties
Andreopoulos, F. M., Beckman, E. J., & Russell, A. J. (1998) · Biomaterials · doi:10.1016/s0142-9612(97)00219-6 · Cited by 127 · see citing works
Carbon coated liquid crystal elastomer film for artificial muscle applications
Shenoy, D. K., Thomsen, D. L., Srinivasan, A., Keller, P., & Ratna, B. R. (2002) · Sensors and Actuators A Physical · doi:10.1016/s0924-4247(01)00793-2 · Cited by 123 · see citing works
Photodeformable Polymers: A New Kind of Promising Smart Material for Micro‐ and Nano‐Applications
Yu, Y., & Ikeda, T. (2005) · Macromolecular Chemistry and Physics · doi:10.1002/macp.200500318 · Cited by 111 · see citing works
Andreopoulos, F. M., Deible, C. R., Stauffer, M. T., Weber, S. G., Wagner, W. R., Beckman, E. J., & Russell, A. J. (1996) · Journal of the American Chemical Society · doi:10.1021/ja954117c · Cited by 95 · see citing works
Optically Switchable Liquid Crystal Photonic Structures
Urbas, A. M., Tondiglia, V. P., Natarajan, L. V., et al. (2004) · Journal of the American Chemical Society · doi:10.1021/ja045143q · Cited by 92 · see citing works
Aligned Growth of Calcite Crystals on a Self-Assembled Monolayer
Travaille, A. M., Donners, J. J. J. M., Gerritsen, J. W., Sommerdijk, N. A. J. M., Nolte, R. J. M., & van Kempen, H. (2002) · Advanced Materials · doi:10.1002/1521-4095(20020404)14:7 · Cited by 91 · see citing works
Vaia, R. (2005) · Nature Materials · doi:10.1038/nmat1400 · Cited by 85 · see citing works
Preparation and characteristics of photocrosslinkable hydrophilic polymer having cinnamate moiety
Nakayama, Y., & Matsuda, T. (1992) · Journal of Polymer Science Part A Polymer Chemistry · doi:10.1002/pola.1992.080301119 · Cited by 61 · see citing works
Degradable, Multifunctional Polymeric Biomaterials with Shape-Memory
Lendlein, A., & Kelch, S. (2005) · Materials Science Forum · doi:10.4028/www.scientific.net/msf.492-493.219 · Cited by 56 · see citing works
Self-citationAkabori, S., Habata, Y., Nakazawa, M., Yamada, Y., Shindo, Y., Sugimura, T., & Sato, S. (1987) · Bulletin of the Chemical Society of Japan · doi:10.1246/bcsj.60.3453 · Cited by 26 · see citing works
Tanaka, H., & Honda, K. (1977) · Journal of Polymer Science Polymer Chemistry Edition · doi:10.1002/pol.1977.170151113 · Cited by 20 · see citing works
Soai, K., Hayashi, H., Shinozaki, A., Umebayashi, H., & Yamada, Y. (1987) · Bulletin of the Chemical Society of Japan · doi:10.1246/bcsj.60.3450 · Cited by 13 · see citing works
Photoreversible reactions of poly(vinyl cinnamylideneacetate) and its model compound
Tanaka, H., & Otomegawa, E. (1974) · Journal of Polymer Science Polymer Chemistry Edition · doi:10.1002/pol.1974.170120516 · Cited by 11 · see citing works
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Behl, M., & Lendlein, A. (2007) · Materials Today · doi:10.1016/s1369-7021(07)70047-0 · Cited by 1,965 · see citing works
Self-citationReview of progress in shape-memory polymers
Liu, C., Qin, H., & Mather, P. T. (2007) · Journal of Materials Chemistry · doi:10.1039/b615954k · Cited by 1,942 · see citing works
Shape-memory polymers and their composites: stimulus methods and applications
Leng, J., Lan, X., Liu, Y., & Du, S. (2011) · Progress in Materials Science · doi:10.1016/j.pmatsci.2011.03.001 · Cited by 1,495 · see citing works
Soft Actuators for Small-Scale Robotics
Hines, L., Petersen, K., Lum, G. Z., & Sitti, M. (2017) · Advanced Materials · doi:10.1002/adma.201603483 · Cited by 1,337 · see citing works
A review of stimuli-responsive shape memory polymer composites
Meng, H., & Li, G. (2013) · Polymer · doi:10.1016/j.polymer.2013.02.023 · Cited by 1,190 · see citing works
Covalent Adaptable Networks (CANs): A Unique Paradigm in Cross-Linked Polymers
Kloxin, C. J., Scott, T. F., Adzima, B. J., & Bowman, C. N. (2010) · Macromolecules · doi:10.1021/ma902596s · Cited by 1,175 · see citing works
Stimulus-responsive shape memory materials: a review
Sun, L., Huang, W. M., Ding, Z., Zhao, Y., Wang, C. C., Purnawali, H., & Tang, C. (2012) · Materials & Design · doi:10.1016/j.matdes.2011.04.065 · Cited by 1,105 · see citing works
Multifunctional Shape‐Memory Polymers
Behl, M., Razzaq, M. Y., & Lendlein, A. (2010) · Advanced Materials · doi:10.1002/adma.200904447 · Cited by 971 · see citing works
Self-citationReprogrammable recovery and actuation behaviour of shape-memory polymers
Lendlein, A., & Gould, O. E. C. (2019) · Nature Reviews Materials · doi:10.1038/s41578-018-0078-8 · Cited by 723 · see citing works
Self-citationLight-triggered self-healing and shape-memory polymers
Habault, D., Zhang, H., & Zhao, Y. (2013) · Chemical Society Reviews · doi:10.1039/c3cs35489j · Cited by 662 · see citing works
A review of stimuli-responsive polymers for smart textile applications
Hu, J., Meng, H., Li, G., & Ibekwe, S. I. (2012) · Smart Materials and Structures · doi:10.1088/0964-1726/21/5/053001 · Cited by 639 · see citing works
Review of electro-active shape-memory polymer composite
Liu, Y., Lv, H., Lan, X., Leng, J., & Du, S. (2009) · Composites Science and Technology · doi:10.1016/j.compscitech.2008.08.016 · Cited by 548 · see citing works
Facile tailoring of thermal transition temperatures of epoxy shape memory polymers
Xie, T., & Rousseau, I. A. (2009) · Polymer · doi:10.1016/j.polymer.2009.02.035 · Cited by 535 · see citing works
Self-folding of polymer sheets using local light absorption
Liu, Y., Boyles, J. K., Genzer, J., & Dickey, M. D. (2012) · Soft Matter · doi:10.1039/c1sm06564e · Cited by 523 · see citing works
Light‐sensitive Intelligent Drug Delivery Systems<sup>†</sup>
Alvarez‐Lorenzo, C., Bromberg, L., & Concheiro, A. (2009) · Photochemistry and Photobiology · doi:10.1111/j.1751-1097.2008.00530.x · Cited by 519 · see citing works
3D Printed Photoresponsive Devices Based on Shape Memory Composites
Yang, H., Leow, W. R., Wang, T., Wang, J., Yu, J., He, K., Qi, D., Wan, C., & Chen, X. (2017) · Advanced Materials · doi:10.1002/adma.201701627 · Cited by 483 · see citing works
Kumpfer, J. R., & Rowan, S. J. (2011) · Journal of the American Chemical Society · doi:10.1021/ja205332w · Cited by 487 · see citing works
Thermally-induced two-way shape memory polymers: Mechanisms, structures, and applications
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Shape-memory polymers for multiple applications in the materials world
Pilate, F., Toncheva, A., Dubois, P., & Raquez, J.-M. (2016) · European Polymer Journal · doi:10.1016/j.eurpolymj.2016.05.004 · Cited by 332 · see citing works
Two-Way 4D Printing: A Review on the Reversibility of 3D-Printed Shape Memory Materials
Lee, A. Y., An, J., & Chua, C. K. (2017) · Engineering · doi:10.1016/j.eng.2017.05.014 · Cited by 326 · see citing works
Behl, M., & Lendlein, A. (2007) · Soft Matter · doi:10.1039/b610611k · Cited by 321 · see citing works
Self-citationBioinspired mechanically adaptive polymer nanocomposites with water-activated shape-memory effect
Mendez, J., Annamalai, P. K., Eichhorn, S. J., Rusli, R., Rowan, S. J., Foster, E. J., & Weder, C. (2011) · Macromolecules · doi:10.1021/ma201502k · Cited by 319 · see citing works
Various shape memory effects of stimuli-responsive shape memory polymers
Meng, H., Mohamadian, H., Stubblefield, M., Jerro, D., Ibekwe, S., Pang, S.-S., & Li, G. (2013) · Smart Materials and Structures · doi:10.1088/0964-1726/22/9/093001 · Cited by 257 · see citing works
Revealing triple-shape memory effect by polymer bilayers
Xie, T., Xiao, X., & Cheng, Y. (2009) · Macromolecular Rapid Communications · doi:10.1002/marc.200900409 · Cited by 251 · see citing works
Evaluation of a degradable shape-memory polymer network as matrix for controlled drug release
Wischke, C., Neffe, A. T., Steuer, S., & Lendlein, A. (2009) · Journal of Controlled Release · doi:10.1016/j.jconrel.2009.05.027 · Cited by 248 · see citing works
Self-citationLiu, Y., Li, Y., Yang, G., Zheng, X., & Zhou, S. (2015) · ACS Applied Materials & Interfaces · doi:10.1021/am5081056 · Cited by 214 · see citing works
Rapidly switchable water-sensitive shape-memory cellulose/elastomer nano-composites
Zhu, Y., Hu, J., Luo, H., Young, R. J., Deng, L., Zhang, S., Fan, Y., & Ye, G. (2012) · Soft Matter · doi:10.1039/c2sm07035a · Cited by 208 · see citing works
Li, Y., Chen, H., Liu, D., Wang, W., Liu, Y., & Zhou, S. (2015) · ACS Applied Materials & Interfaces · doi:10.1021/acsami.5b02940 · Cited by 206 · see citing works
Progress of shape memory polymers and their composites in aerospace applications
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Wu, L., Jin, C., & Sun, X. (2011) · Biomacromolecules · doi:10.1021/bm1012162 · Cited by 161 · see citing works
Kumar, U. N., Kratz, K., Wagermaier, W., Behl, M., & Lendlein, A. (2010) · Journal of Materials Chemistry · doi:10.1039/b923000a · Cited by 148 · see citing works
Self-citationReview on the Functional Determinants and Durability of Shape Memory Polymers
Pretsch, T. (2010) · Polymers · doi:10.3390/polym2030120 · Cited by 138 · see citing works
Raquez, J., Vanderstappen, S., Meyer, F., Verge, P., Alexandre, M., Thomassin, J., Jérôme, C., & Dubois, P. (2011) · Chemistry – A European Journal · doi:10.1002/chem.201100496 · Cited by 133 · see citing works
A biodegradable shape-memory nanocomposite with excellent magnetism sensitivity
Yu, X., Zhou, S., Zheng, X., Guo, T., Xiao, Y., & Song, B. (2009) · Nanotechnology · doi:10.1088/0957-4484/20/23/235702 · Cited by 111 · see citing works
Digital manufacture of shape changing components
Yu, K., Dunn, M. L., & Qi, H. J. (2015) · Extreme Mechanics Letters · doi:10.1016/j.eml.2015.07.005 · Cited by 76 · see citing works
Design of multistimuli-responsive shape-memory polymer materials by reactive extrusion
Pilate, F., Mincheva, R., De Winter, J., Gerbaux, P., Wu, L., Todd, R., Raquez, J.-M., & Dubois, P. (2014) · Chemistry of Materials · doi:10.1021/cm5020543 · Cited by 78 · see citing works
Carrico, J. D., Tyler, T., & Leang, K. K. (2017) · International Journal of Smart and Nano Materials · doi:10.1080/19475411.2018.1438534 · Cited by 78 · see citing works
Li, W., Liu, Y., & Leng, J. (2014) · RSC Adv. · doi:10.1039/c4ra10716k · Cited by 71 · see citing works
Hyperbranched polycoumarates with photofunctional multiple shape memory
Wang, S., Kaneko, D., Okajima, M., Yasaki, K., Tateyama, S., & Kaneko, T. (2013) · Angewandte Chemie International Edition · doi:10.1002/anie.201305647 · Cited by 54 · see citing works
Modeling the mechanics of light activated shape memory polymers
Sodhi, J. S., & Rao, I. J. (2010) · International Journal of Engineering Science · doi:10.1016/j.ijengsci.2010.05.003 · Cited by 50 · see citing works
Influence of in vitro degradation of a biodegradable nanocomposite on its shape memory effect
Yu, X., Zhou, S., Zheng, X., Xiao, Y., & Guo, T. (2009) · The Journal of Physical Chemistry C · doi:10.1021/jp9022986 · Cited by 38 · see citing works
Biodegradable shape memory nanocomposites with thermal and magnetic field responsiveness
Zhang, X., Lu, X., Wang, Z., Wang, J., & Sun, Z. (2013) · Journal of Biomaterials Science Polymer Edition · doi:10.1080/09205063.2012.735098 · Cited by 28 · see citing works
Xu, M., Cong, Y., & Zhang, B. (2017) · Liquid Crystals · doi:10.1080/02678292.2017.1308022 · Cited by 17 · see citing works
Synthesis and characterization of N,N-bis(2-hydroxyethyl) cinnamamide as a photo-responsive monomer
Jin, C., Sun, X., & Wu, L. (2011) · Designed Monomers and Polymers · doi:10.1163/138577210x541196 · Cited by 17 · see citing works
- Authors
- Jiang, H. Y., Kelch, S., & Lendlein, A.
- Affiliations
- RWTH Aachen University (DE)
- Corresponding author
- Lendlein, A.
- ORCID
- Lendlein, A.
- Venue
- Advanced Materials
- Publisher
- Wiley
- Published
- 2006-05-05
- Volume
- 18
- Issue
- 11
- Pages
- 1471-1475
- ISSN
- 0935-9648 (ISSN-L)
- 1521-4095
- OpenAlex
- W2043404570
- Cited by
- 631
- References
- 48
- Citations by year
- 2026: 9 · 2025: 20 · 2024: 31 · 2023: 25 · 2022: 30 · 2021: 32 · 2020: 26 · 2019: 47 · 2018: 34 · 2017: 38 · 2016: 47 · 2015: 34 · 2014: 50 · 2013: 49 · 2012: 33
- FWCI
- 48.00
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Advanced Materials (publishedVersion)
- RWTH Publications (RWTH Aachen) (submittedVersion)
- Topics
- Physical Sciences › Engineering › Mechanical Engineering › Advanced Materials and Mechanics
- Physical Sciences › Materials Science › Polymers and Plastics › Polymer composites and self-healing
- Physical Sciences › Materials Science › Materials Chemistry › Photochromic and Fluorescence Chemistry
- Keywords
- shape memory polymers, azobenzene, liquid crystal elastomers, photoinduced bending, photoresponsive gels, volume change, polymer functionalization, medical devices
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