DOI: 10.1021/la9021323 14093 Langmuir 2009, 25(24), 14093–14099 Published on Web 10/13/2009 pubs.acs.org/Langmuir © 2009 American Chemical Society Highly Ductile Multilayered Films by Layer-by-Layer Assembly of Oppositely Charged Polyurethanes for Biomedical Applications † Paul Podsiadlo, ‡ Ming Qin, ‡ Meghan Cuddihy, ‡ Jian Zhu, ‡ Kevin Critchley, ‡ Eugene Kheng, § Amit K. Kaushik, § Ying Qi, # Hyoung-Sug Kim, z,þ Si-Tae Noh, z Ellen M. Arruda, §,3 Anthony M. Waas, ) ,§ and Nicholas A. Kotov* ,‡,^,# ‡ Departments of Chemical Engineering and § Mechanical Engineering and ) Aerospace Engineering and ^ Biomedical Engineering and # Materials Science and Engineering and 3 Program in Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, z Department of Chemical Engineering, Hanyang University, Ansan 425-791, Kyounggi-Do, South Korea, and þ R&D Center, Hepce Chemical Company, Ltd., Ansan 425-836, Kyounggi-Do, South Korea Received June 15, 2009. Revised Manuscript Received August 31, 2009 Multilayered thin films prepared with the layer-by-layer (LBL) assembly technique are typically “brittle” composites, while many applications such as flexible electronics or biomedical devices would greatly benefit from ductile, and tough nanostructured coatings. Here we present the preparation of highly ductile multilayered films via LBL assembly of oppositely charged polyurethanes. Free-standing films were found to be robust, strong, and tough with ultimate strains as high as 680% and toughness of ∼30 MJ/m 3 . These results are at least 2 orders of magnitude greater than most LBL materials presented until today. In addition to enhanced ductility, the films showed first-order biocompatibility with animal and human cells. Multilayered structures incorporating polyurethanes open up a new research avenue into the preparation of multifunctional nanostructured films with great potential in biomedical applications. Introduction Multilayered nanostructured thin films prepared with the layer- by-layer (LBL) assembly technique have gained wide popularity in the past decade. 1 Since its inception in the early 1990 0 s, the LBL field has experienced rapid growth, and today it is being utilized for a wide variety of applications, ranging from nanocomposites, 2-4 drug delivery platforms, 5,6 superhydrophobic coatings, 7 fuel cell and photovoltaic membranes, 8 microbatteries, 9,10 and onto solid-state memory devices. 11 Overall, the technique has shown remarkable versatility in combining a variety of components into functional structures, including nanoparticles, 12-14 nanotubes and nano- wires, 2,15,16 nanoplates, 3,4 dendrimers, 17 polysaccharides, 18 poly- peptides and DNA, 19-21 proteins, 22 and viruses. 9,10,23,24 Most of the LBL films presented until today can be considered in general as nonductile structures, while many applications, such as flexible electronics or biomedical coatings, would greatly benefit from enhanced ductility and toughness. In fact, nearly all LBL films show elastic moduli typically of a few gigapascals 2,3,25-29 (as high as 106 GPa 4 ) and only a few percentiles of ultimate strain. Two recent examples of hydrated multilayers and LBL tubes were shown to be much “softer” in nature, with moduli of only tens to a few hundreds of megapascals; however, no strain data were provided. 30,31 In † Part of the “Langmuir 25th Year: Self-assembled polyelectrolyte multi- layers: structure and function” special issue. *To whom correspondence should be addressed. Tel.: (734) 763-8768. Fax: (734) 764-7453. E-mail: kotov@umich.edu. (1) Decher, G. Science 1997, 277, 1232. (2) Mamedov, A. A.; Kotov, N. A.; Prato, M.; Guldi, D. M.; Wicksted, J. P.; Hirsch, A. Nat. Mater. 2002, 1, 190. (3) Tang, Z. Y.; Kotov, N. A.; Magonov, S.; Ozturk, B. Nat. Mater. 2003, 2, 413. (4) Podsiadlo, P.; Kaushik, A. K.; Arruda, E. M.; Waas, A. M.; Shim, B. S.; Xu, J. D.; Nandivada, H.; Pumplin, B. G.; Lahann, J.; Ramamoorthy, A.; Kotov, N. A. Science 2007, 318, 80. (5) Wood, K. C.; Chuang, H. F.; Batten, R. D.; Lynn, D. M.; Hammond, P. T. Proc. Natl. Acad. Sci. U.S.A. 2006, 103, 10207. (6) Wood, K. C.; Zacharia, N. S.; Schmidt, D. J.; Wrightman, S. N.; Andaya, B. J.; Hammond, P. T. Proc. Natl. Acad. Sci. U.S.A. 2008, 105, 2280. (7) Zhai, L.; Cebeci, F. C.; Cohen, R. E.; Rubner, M. F. Nano Lett. 2004, 4, 1349. (8) Tokuhisa, H.; Hammond, P. T. Adv. Funct. Mater. 2003, 13, 831. (9) Nam, K. T.; Kim, D. W.; Yoo, P. J.; Chiang, C. Y.; Meethong, N.; Hammond, P. T.; Chiang, Y. M.; Belcher, A. M. Science 2006, 312, 885. (10) Nam, K. T.; Wartena, R.; Yoo, P. J.; Liau, F. W.; Lee, Y. J.; Chiang, Y. M.; Hammond, P. T.; Belcher, A. M. Proc. Natl. Acad. Sci. U.S.A. 2008, 105, 17227. (11) Lee, J. S.; Cho, J.; Lee, C.; Kim, I.; Park, J.; Kim, Y. M.; Shin, H.; Lee, J.; Caruso, F. Nat. Nanotechnol. 2007, 2, 790. (12) Kotov, N. A.; Dekany, I.; Fendler, J. H. J. Phys. Chem. 1995, 99, 13065. (13) Keller, S. W.; Kim, H. N.; Mallouk, T. E. J. Am. Chem. Soc. 1994, 116, 8817. (14) Cooper, T. M.; Campbell, A. L.; Crane, R. L. Langmuir 1995, 11, 2713. (15) Podsiadlo, P.; Choi, S. Y.; Shim, B.; Lee, J.; Cuddihy, M.; Kotov, N. A. Biomacromolecules 2005, 6, 2914. (16) Podsiadlo, P.; Sui, L.; Elkasabi, Y.; Burgardt, P.; Lee, J.; Miryala, A.; Kusumaatmaja, W.; Carman, M. R.; Shtein, M.; Kieffer, J.; Lahann, J.; Kotov, N. A. Langmuir 2007, 23, 7901. (17) He, J. A.; Valluzzi, R.; Yang, K.; Dolukhanyan, T.; Sung, C. M.; Kumar, J.; Tripathy, S. K.; Samuelson, L.; Balogh, L.; Tomalia, D. A. Chem. Mater. 1999, 11, 3268. (18) Lvov, Y.; Onda, M.; Ariga, K.; Kunitake, T. J. Biomater. Sci., Polym. Ed. 1998, 9, 345. (19) Richert, L.; Lavalle, P.; Vautier, D.; Senger, B.; Stoltz, J. F.; Schaaf, P.; Voegel, J. C.; Picart, C. Biomacromolecules 2002, 3, 1170. (20) Boulmedais, F.; Ball, V.; Schwinte, P.; Frisch, B.; Schaaf, P.; Voegel, J. C. Langmuir 2003, 19, 440. (21) Lvov, Y.; Decher, G.; Sukhorukov, G. Macromolecules 1993, 26, 5396. (22) Lvov, Y.; Ariga, K.; Kunitake, T. Chem. Lett. 1994, 2323. (23) Yoo, P. J.; Nam, K. T.; Qi, J. F.; Lee, S. K.; Park, J.; Belcher, A. M.; Hammond, P. T. Nat. Mater. 2006, 5, 234. (24) Tang, Z. Y.; Wang, Y.; Podsiadlo, P.; Kotov, N. A. Adv. Mater. 2006, 18, 3203. (25) Jiang, C. Y.; Markutsya, S.; Pikus, Y.; Tsukruk, V. V. Nat. Mater. 2004, 3, 721. (26) Ko, H.; Jiang, C. Y.; Shulha, H.; Tsukruk, V. V. Chem. Mater. 2005, 17, 2490. (27) Gunawidjaja, R.; Jiang, C. Y.; Peleshanko, S.; Ornatska, M.; Singamaneni, S.; Tsukruk, V. V. Adv. Funct. Mater. 2006, 16, 2024. (28) Lin, Y. H.; Jiang, C.; Xu, J.; Lin, Z. Q.; Tsukruk, V. V. Adv. Mater. 2007, 19, 3827. (29) Nolte, A. J.; Rubner, M. F.; Cohen, R. E. Macromolecules 2005, 38, 5367. (30) Schoeler, B.; Delorme, N.; Doench, I.; Sukhorukov, G. B.; Fery, A.; Glinel, K. Biomacromolecules 2006, 7, 2065. (31) Cuenot, S.; Alem, H.; Louarn, G.; Demoustier-Champagne, S.; Jonas, A. M. Eur. Phys. J. E 2008, 25, 343.