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Engineered Asymmetric Composite Membranes with Rectifying Properties Liping Wen, Kai Xiao, Annadanam V. Sesha Sainath, Motonori Komura, Xiang-Yu Kong, Ganhua Xie, Zhen Zhang, Ye Tian, Tomokazu Iyoda,* and Lei Jiang* Solid-state synthetic nanochannels or membranes with greater flexibility in terms of shape and size, superior robustness, and improved surface properties can be used as abiotic analogs of biomembranes that regulate ion permeation through asymmetric cell membranes and are significant for performing proper cellular and biological processes.[1,2] At present, a variety of materials and technologies have been used to develop these artificial channels and membranes that can respond to some external stimulus, such as pH, ions, temperature, light, and electric potential.[3–7] However, for most of these nanochannels or membranes, it is hard to simultaneously control the porosity, thickness, and smart functions. Endowing these artificial nanochannels or membranes with controllable porosity, thickness, and smart functions similar to biomembranes is still a challenging task. Highly periodically ordered nanoporous membranes arising from the microphase separation of block copolymers (BCs) are attracting increasing attention in producing nanoporous membranes that can be used in sensing, filtrating, energy conversion, and storage systems, as well as in scaffolds and templates for efficient fabrication of various nanoscopic structures.[8–24] However, such nanoporous membranes are either symmetric structures or asymmetric membrane with too large pore size, which has symmetric ionic transport property, both of membranes cannot mimic the rectifying properties of biological ion channels.[25–29] Here, we report for the first time the preparation and characterization of an asymmetric composite membrane with rectifying properties via the phase separation of two novel synthesized BCs that can form an asymmetric geometry with two types of high-density visualized straight

Prof. L. Wen, Dr. X.-Y. Kong, Prof. L. Jiang Laboratory of Bioinspired Smart Interfacial Science Technical Institute of Physics and Chemistry Chinese Academy of Sciences Beijing 100190, P. R. China E-mail: [email protected] K. Xiao, G. Xie, Z. Zhang, Dr. Y. Tian Beijing National Laboratory for Molecular Sciences (BNLMS) Key Laboratory of Organic Solids Institute of Chemistry Chinese Academy of Sciences Beijing 100190, P. R. China Dr. A. V. S. Sainath, Dr. M. Komura, Prof. T. Iyoda Division of Integrated Molecular Engineering Chemical Resources Laboratory Tokyo Institute of Technology R1-25 4259 Nagatsuta Midori Ku, Yokohama 226-8503, Japan E-mail: [email protected]

DOI: 10.1002/adma.201504960

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channels of poly(ethylene oxide) (PEO) domains with different sizes. In addition, a pH stimulus-responsive molecule that can form a compositional asymmetric system is modified via plasma-induced grafting technique. The two developed BCs are PEO272-b-PMA(Chal)97 (BC-1) and PEO114-b-PMA(rChal)57 (BC2), which contain chalcone mesogen in the side chain whose parts can be photocrosslinked after irradiation with UV light (Figure S1–S3, Supporting Information). The stimulus-responsive molecule is poly(vinylpyridine) (P4VP) that can respond to the external pH environment. Compared with reported artificial membranes, the engineered asymmetric composite membrane has the advantages of simultaneously controllable ionic rectification, porosity, and film thickness. This system, for example, may potentially spark further experimental and theoretical efforts to exploit more complex “smart” membrane systems. As shown in Scheme 1, the asymmetric compositional membranes were prepared via phase separation of BCs and plasmainduced grafting. First, cellulose acetate (CA) was adopted as a sacrificial layer and was pre-coated on a substrate (≈100 nm thick) that could be quickly dissolved away with acetone. Then, the microphase-separated BC-1 was cast from a 4 wt% chloroform solution onto a sacrificial CA layer followed by annealing at 80 °C for 24 h under vacuum and photocrosslinked using 313 nm UV irradiation. Later, a microphase-separated BC-2 film was cast onto the BC-1 film. After the two processes of annealing and photocrosslinking, we obtained asymmetric geometric nanoporous membranes. Next, P4VP was added to the monolayer and laminated membranes via plasma-induced grafting, which offered an effective method for nanoscale surface engineering of materials and could easily and precisely functionalize a specific local area.[30] Thus, combining the plasma-induced grafting technique and phase separation of BCs, we synthesized asymmetric composite membranes with simultaneously controllable rectification, porosity, and film thickness. These engineered asymmetric compositional membranes could be exfoliated from the CA layer and easily transferred onto any other substrate. Here, the CA layer was ready to be removed and formed a freestanding membrane in the following manner. After immersion in acetone, the partly released membrane with the substrate was gently transferred into water for complete exfoliation. Consequently, the entire membrane was released from the substrate and floated on the surface of the water. This membrane could be easily extracted using a metal wire ring; it retained its shape without wrinkles and breaking (center in scheme 1). The monolayer BC nanostructures were imaged using atomic force microscopy (AFM). Figure 1A,B show typical AFM images of PEO272-b-PMA(Chal)97 and PEO114-b-PMA(rChal)57. For both

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Scheme 1. Fabrication of asymmetric composite membranes. i) Spin-coating cellulose acetate (CA, gray; 8 wt% acetone solution, 2000 rpm, 60 s) onto a silicon wafer substrate, ii) spin-coating BC-1 (blue; 4 wt% CHCl3 solution, 1000 rpm, 30 s) onto a sacrificial CA layer (gray), iii) annealing at 80 °C for 2 h under vacuum, iv) crosslinking the chalcone mesogens in the side chain of the PMA(Chal) segment upon UV irradiation (313 nm, 5 mW cm−2, 10 min), v) spin-coating BC-2 (yellow; 2 wt% toluene solution, 2000 rpm, 30 s) onto a first block copolymer layer (blue), vi) annealing at 80 °C for 2 h under vacuum, vii) crosslinking the reverse chalcone mesogens in the side chain of the PMA(rChal) segment upon UV irradiation (313 nm, 5 mW cm−2, 10 min), viii) plasma-induced grafting of P4VP, ix) cleanup of the unreacted P4VP with solvents, x) exfoliating the functionalized laminated membrane from the substrate, xi) exfoliating the monolayer membrane from the substrate, and xii) extracting the exfoliated membrane out of the water surface. The structural formulas in the left corner are the two novel synthesized block copolymers.

of the BCs, the PEO blocks were cylinders and/or spheres with perpendicular orientations to the surface, which was also supported by the transmission electron microscopy (TEM) images (Figure S4, Supporting Information). Meanwhile, after a 2 wt% toluene solution of PEO114-b-PMA(rChal)57 was cast onto the photocrosslinked PEO272-b-PMA(Chal)97 layer, an asymmetric composite membrane was prepared. AFM images of both sides of the membrane (Figure 1C,D) showed the same aligned hexagonal cylinder structures when BCs of PEO114-b-PMA(rChal)57 and PEO272-b-PMA(Chal)97 were used on the sacrificial CA layer. The diameter was approximately 5.3 ± 1.4 nm for the top layer of PEO114-b-PMA(rChal)57 (Figure 1C) and 10.2 ± 2.1 nm for the back side of PEO272-b-PMA(Chal)97 (Figure 1D). Apparently, there were some defects on the back side of the membrane, which was different from the front morphology that was obtained from the monolayer of PEO272-b-PMA(Chal)97. The reason for this behavior may be attributed to the assembly method in which the BC on the top was more easily assembled than the BC on the bottom. Clearly, the domain on one side of the laminated membrane was large, the domain on the other side was small, and their geometries were asymmetric. Figure 2A shows the 2D grazing-incidence small-angle X-ray scattering (GISAXS) pattern obtained at 25 °C, which contained several strong scattering peaks in the 2θf direction. GISAXS measurements were performed to examine the nanostructures

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and orientations of the transferred membranes.[31–33] The inplane scattering profile contained four scattering peaks with relative scattering vector lengths from the specular reflection position of 1, (3)1/2, (4)1/2, and (7)1/2.[34] These scattering peaks were characteristic of a hexagonally packed cylinder structure, indicating that the cylindrical microdomains of the PEO block (which was the minor component in the diblock copolymer) aligned in a direction perpendicular to the membrane plane and, furthermore, were hexagonally packed in the membrane plane. The peaks at 2θf = 0.22263° and 0.3158° corresponded to d-spacings of 32.536 nm and 22.12 nm, which were assigned to the distances between the PEO cylinders of PEO272-b-PMA(Chal)97 and PEO114-b-PMA(rChal)57, respectively (Figure 2B). Figure 2C–E show GISAXS 2D images that were obtained from the hexagonally arranged cylinder domains stemming from the monolayers of PEO272-b-PMA(Chal)97, PEO114-bPMA(rChal)57, and the asymmetric composite membrane made using PEO114-b-PMA(rChal)57 and PEO272-b-PMA(Chal)97, from which the bright dots in each side of in-plane profiles fit very well with the peaks shown in Figure 2B. The rectifying properties of these composite membranes before and after modification with P4VP were examined by measuring the ionic current, which was performed using a simple electrochemical device (Figure S5, Supporting Information). Figure 3A shows the I–V properties of the naked


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COMMUNICATION Figure 1. A,B). AFM morphology of PEO272-b-PMA(Chal)97 and PEO114-b-PMA(rChal)57; C,D). AFM morphology of the front and back side of an asymmetric composite membrane made using PEO114-b-PMA(rChal)57 (up) and PEO272-b-PMA(Chal)97 (down); diameter ≈10.5 nm, center-to-center distance ≈32 nm to PEO272-b-PMA(Chal)97; diameter ≈5.5 nm, center-to-center distance ≈22 nm to PEO114-b-PMA(rChal)57.

asymmetric composite membrane, which exhibited linear I–V curves over the pH range from 2.8 to 10.2. However, the ionic rectification was different for the functionalized asymmetric composite membranes. There was a sharp increase in the transmembrane ionic current when a positive voltage was applied (anode facing the nonmodified side) at pH 2.8 (Figure 3B). Because the original P4VP-functionalized BC was neutral, the anions and cations in the electrolyte could simultaneously transport across the channel driven by the potential, ohmic conductor, and linear I–V curves (Figure 3C, middle). When the P4VP-functionalized membrane was placed into an acidic ambient environment, the membrane's surface was positively charged due to proton uptake, which resulted in an anionselective, hydrophilic state. In this case, the anions preferred to flow from the grafted PEO domains (Figure 3C, right). After the P4VP-functionalized nanochannel system was placed in an alkali environment, the protons that were taken up released and recovered to the original neutral and hydrophobic state, and then, the ohmic conductor was recovered. If the top and bottom layer membranes were exchanged, we obtained the same trend in ionic current rectification (Figure S6, Supporting Information). Furthermore, the rectifying properties of these two monolayer membranes before and after modification with P4VP were examined by the measuring ionic current. Both of

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the membranes exhibited Ohmic characteristics (Figure S7, Supporting Information). Figure 4 shows the influence of the pH on the ionic transport properties of the membrane, which was defined as the ratio of the current changes measured at a given voltage (2 V) versus the current measured at the same voltage but with the reverse bias (i.e., −2 V). Before functionalization, the ratios of the monolayer membrane remained at approximately 1.0–1.2 as the pH changed from 2.8 to 10.2. After modification, the ratio of the engineered membrane at pH 10.2 was 1.16 ± 0.20, which was lower than 1.36 ± 0.22 calculated at pH 2.8. For the asymmetric composite membrane before modification, the current ratios remained at approximately 1.1 regardless of the pH of the electrolytes that were used. After modification, the ratio of the functionalized membrane at pH 2.8 was 2.15 ± 0.20; however, the ratios calculated at pH 6.5 and pH 10.2 remained unchanged. Only the engineered composite membranes showed clear ionic current rectification, which resulted from the asymmetry, including the geometry and chemical composition, and resulted in changes in the surface charges and wettability with the changing ambient pH (Figure S8, Supporting Information). The aforementioned experimental results can be quantitatively supported by a further theoretical model based on solving



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Figure 2. A) GISAXS characterization: αi is the incident angle where the X-ray beam impinges on the membrane surface, αf and 2θf are the exit angles of the X-ray beam with respect to the membrane surface and to the incidence plane, respectively, and qx, qy, and qz are the components of the scattering vector q; B) In-plane profiles of PEO114-b-PMA(rChal)57, PEO272-b-PMA(Chal)97 and the asymmetric composite membrane made using PEO114b-PMA(rChal)57 and PEO272-b-PMA(Chal)97; C–E) 2D GISAXS images of PEO114-b-PMA(rChal)57, PEO272-b-PMA(Chal)97 and the asymmetric composite membrane made using PEO114-b-PMA(rChal)57 and PEO272-b-PMA(Chal)97.

the Poisson and Nernst–Planck (PNP) equations. The Nernst– Plank[35] equation is: J i = −Di ( ∇c i + zi c i ∇φ ) , i = + , −

(1)

where i = + stands for cations and i = − stands for anions and the steady state continuity equation and the Poisson equation, 760


∇J i = 0,i = + , − , F2 ∇ 2φ = (c − − c + ) ε RT

(2)

where Ji is the ion flux, Di is the diffusion coefficient, zi is the charge number of the ionic species i, φ denotes the local


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COMMUNICATION Figure 3. Current–voltage (I–V) properties of the asymmetric composite membranes made from PEO114-b-PMA(rChal)57 (top) and PEO272-bPMA(Chal)97 (bottom), which were measured in 0.01 M KCl with different pH values. I–V properties of laminated membranes A) before and B) after asymmetric chemical modification with P4VP; the I–V characteristics were recorded under symmetric electrolyte conditions at pH 2.8 (squares), 6.5 (circles), and 10.2 (triangles).

dimensionless electric potential, and Ci refers to the concentration of species i. Combining these electrostatic models (refer to the Poisson equations and surface charge density) and transport of diluted species (refer to the Nernst–Planck equation), we simulated the ionic current rectification by calculating the concentration distribution inside the nanochannel membrane using COMSOL Multiphysics 4.4. As shown in Figure 5a, the ion concentration profile of the naked bilayer membrane was not affected by the bulk concentration (10 mol m−3) under varied applied electric field (±1 V); thus, it did not rectify the ionic current. After placing the functionalized asymmetric

Figure 4. Ionic current rectification of composite membranes before and after modification with P4VP, which were measured in different pH conditions (Sparse, pH 2.8; None, pH 6.5; Dense, pH 10.2).

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bilayer membranes into an acidic environment (0.01 C m−2), the concentration profiles were different; that is, the concentration obtained at 1 V was much higher than the negative one, which was the main cause of the rectified ionic current (Figure 5b). When the composite membrane was in a neutral or basic environment, the concentration profile was the same as that in the naked composite membrane, and no rectification of the I–V curve was obtained; the positive surface charge played a key role in the concentration distribution. At 1 V (the anode faced the grafted side and the cathode faced the naked one), anions were driven to the grafted side (anode) due to the electric static potential (Figure S9, Supporting Information). This phenomenon increased the conductance and the ion current. At −1 V (the cathode faced the grafted side of the membrane), the situation was reversed: Anions were driven to the naked region. This phenomenon decreased the conductance and ionic current. The net surface charge was positive, and anions were the majority of the carriers. With external applied voltage, the electric field direction drove the ions, which also contributed to the accumulation of anions. Apparently, the anions accumulated to a higher degree when there was a positive voltage applied than when there was a negative voltage. Therefore, the asymmetric geometric shape of the membrane contributed to the asymmetric distribution of ions near the surface, which was the quantitative explanation for the current rectification property of this artificial pH-induced smart membrane. As shown in Figure 5, the theoretical I–V curves of the membranes before and after modification from the PNP model showed excellent agreement with the experimental observations. In summary, we experimentally demonstrated an engineered asymmetric composite membrane, which is formed via the phase separation of two novel photocrosslinkable liquid



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Figure 5. Numerical simulation of an asymmetric composite membrane. a) Before (naked) and b) after modification with P4VP molecules. The calculated ion concentration profile inside the nanochannel membrane reveals that the ionic rectification results from the ion concentration enrichment at positive voltages and depletion at negative voltages. In this 2D configuration, the symmetric membrane does not rectify the ionic current. By sequentially introducing structural and electrostatic models, the rectification ratio is generated.

crystalline BCs and a pH-responsive molecule added via plasmainduced grafting. This system had the advanced feature of providing simultaneous control over porosity, film thickness, and pH-tunable asymmetric ionic transport properties. The responsive properties of this composite membrane were significantly dependent on the combination of the asymmetric geometry and the surface charge. Increasing the BC layer and decreasing the environmental pH improved the asymmetric responsive capabilities. Theoretical simulations provided insight into the origin of the geometry-charge-dependent ionic rectification and were in qualitative agreement with the experimental observations. We believe that this asymmetric composite system can be extended to higher levels of functionality by optimizing the composition of the BCs and functionalizing more complicated functional molecules. This novel system is an example of the beginning of engineered asymmetric composite membranes and advances further toward the development of “smart” membranes for real-world applications, such as membrane-based material applications ranging from separation, energy conversion, sensing, etc.

Experimental Section Materials: The novel developed photocrosslinkable liquid-crystalline BCs, PEO272-b-PMA(Chal)97 and PEO114-b-PMA(rChal)57, used in this study were prepared via atom-transfer radical polymerization (ATRP) of the new methacrylate monomer bearing a chalcone mesogen in the side chain from the PEO macroinitiator. The synthetic procedures of PEOmb-PMA(rChal/Chal)n are described elsewhere.[36] Peak assignments of 1H NMR spectrum in CDCl3 are given in Figure S1 (Supporting Information). Gel permeation chromatography (GPC) sample report of PEO272-b-PMA(Chal)97 gave a number-average molecular weight Mn of 38 494 g mol−1, a weight-average molecular weight of 45 886 g mol−1,

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and Mw/Mn = 1.19203. For the sample of PEO114-b-PMA(rChal)57, the GPC gave a number-average molecular weight Mn of 27 544 g mol−1, a weight-average molecular weight of 37 814 g mol−1, and Mw/Mn = 1.37286 (Figure S2, Supporting Information). Thermal properties of the BCs (Figure S3, Supporting Information) were investigated on a DSC8000 (PerkinElmer) instrument with indium and zinc employed for the temperature calibration. Samples of ≈2.0 mg were sealed in aluminum pans, and a nitrogen gas purge with a flux of ≈20 mL min−1 was used to prevent oxidative degradation of samples during the temperature scan. The samples were heated at a rate of 10 °C min−1. Membrane Characterization: The membrane characterization was performed via TEM, AFM, and GISAXS. TEM images were obtained using a Hitachi 7000 transmission electron microscope. AFM images were collected in a tapping mode using Dimension 3000 (Digital Instruments/Veeco) and NanoScope IV (Digital Instruments/Veeco) scanning force microscopes. GISAXS measurements were performed using a Nano-Viewer with a CCD camera (Rigaku Corp. Japan). The X-ray source was a laboratory specification 18 W Cu Kα radiation beam (λ = 1.541 Å) converged and monochromatized by a Confocal Max Flax mirror. The X-ray generator was a Rigaku Micro7 rotating anode generator (40 kV, 30 mA). The diameter of the X-ray beam was controlled by a three-slit optical system and was set to 250 µm. The incidence angle of the X-ray was set to 0.20°– 0.21° near the critical reflection angle of a silicon wafer to effectively obtain the in-plane signals. Current Measurement: The ionic transport properties of the membranes before and after plasma treatment were studied by analyzing the ionic current, which was measured by a Keithley 6487 picoammeter (Keithley Instruments, Cleveland, OH). The prepared monolayer and laminated membranes made by spin coating phaseseparated BCs and plasma-induced polymerization of P4VP was mounted between two chambers of the electrical cell. Ag/AgCl electrodes were used to apply a transmembrane potential across the membrane. The main transmembrane potential used in this work was evaluated and the scanning voltage varied from −1 to +1 V with a 20 s period. The electrolyte was 0.01 M KCl whose pH was adjusted with 1 M HCl and KOH solutions. Each test was repeated five times to obtain an average current value at different voltages. The testing temperature was 22 °C.


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Supporting Information is available from the Wiley Online Library or from the author.

Acknowledgements This work was supported by the National Research Fund for Fundamental Key Projects (2011CB935703), National Natural Science Foundation (21171171, 21434003, 91427303, 21201170, 91127025, 21421061), and the Key Research Program of the Chinese Academy of Sciences (KJZD-EW-M03). Received: October 8, 2015 Published online: December 2, 2015

[1] C. R. Martin, Z. S. Siwy, Science 2007, 317, 331. [2] L. Wen, X. Hou, Y. Tian, F.-Q. Nie, Y. Song, J. Zhai, L. Jiang, Adv. Mater. 2010, 22, 1021. [3] X. Hou, W. Guo, L. Jiang, Chem. Soc. Rev. 2011, 40, 2385. [4] D. Wu, F. Xu, B. Sun, R. Fu, H. He, K. Matyjaszewski, Chem. Rev. 2012, 112, 3959. [5] R. Chantiwas, S. Park, S. A. Soper, B. C. Kim, S. Takayama, V. Sunkara, H. Hwang, Y.-K. Cho, Chem. Soc. Rev. 2011, 40, 3677. [6] G. Soler-Illia, O. Azzaroni, Chem. Soc. Rev. 2011, 40, 1107. [7] M. Park, C. Harrison, P. M. Chaikin, R. A. Register, D. H. Adamson, Science 1997, 276, 1401. [8] T. L. Morkved, M. Lu, A. M. Urbas, E. E. Ehrichs, H. M. Jaeger, P. Mansky, T. P. Russell, Science 1996, 273, 931. [9] S. Ouk Kim, H. H. Solak, M. P. Stoykovich, N. J. Ferrier, J. J. de Pablo, P. F. Nealey, Nature 2003, 424, 411. [10] A. Checco, A. Rahman, C. T. Black, Adv. Mater. 2014, 26, 886. [11] M. Radjabian, V. Abetz, Adv. Mater. 2015, 27, 352. [12] J. Bang, U. Jeong, D. Y. Ryu, T. P. Russell, C. J. Hawker, Adv. Mater. 2009, 21, 4769. [13] A. Chen, M. Komura, K. Kamata, T. Iyoda, Adv. Mater. 2008, 20, 763. [14] H. Yu, X. Qiu, S. P. Nunes, K.-V. Peinemann, Angew. Chem. Int. Ed. 2014, 53, 10072.

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Supporting Information

[15] A. S. Zalusky, R. Olayo-Valles, J. H. Wolf, M. A. Hillmyer, J. Am. Chem. Soc. 2002, 124, 12761. [16] K.-V. Peinemann, V. Abetz, P. F. W. Simon, Nat. Mater. 2007, 6, 992. [17] M. Aizawa, J. M. Buriak, J. Am. Chem. Soc. 2005, 127, 8932. [18] J. S. Lee, A. Hirao, S. Nakahama, Macromolecules 1988, 21, 274. [19] G. Liu, N. Hu, X. Xu, H. Yao, Macromolecules 1994, 27, 3892. [20] Y. Wang, C. He, W. Xing, F. Li, L. Tong, Z. Chen, X. Liao, M. Steinhart, Adv. Mater. 2010, 22, 2068 [21] V. Z.-H. Chan, J. Hoffman, V. Y. Lee, H. Iatrou, A. Avgeropoulos, N. Hadjichristidis, R. D. Miller, E. L. Thomas, Science 1999, 286, 1716. [22] T. Thurn-Albrecht, R. Steiner, J. DeRouchey, C. M. Stafford, E. Huang, M. Bal, M. Tuominen, C. J. Hawker, T. P. Russell, Adv. Mater. 2000, 12, 787. [23] T. Thurn-Albrecht, J. Schotter, G. A. Kästle, N. Emley, T. Shibauchi, L. Krusin-Elbaum, K. Guarini, C. T. Black, M. T. Tuominen, T. P. Russell, Science 2000, 290, 2126. [24] D. Mecerreyes, E. Huang, T. Magbitang, W. Volksen, C. J. Hawker, V. Y. Lee, R. D. Miller, J. L. Hedrick, High Perform. Polym. 2001, 13, S11. [25] H. Yu, T. Iyoda, T. Ikeda, J. Am. Chem. Soc. 2006, 128, 11010. [26] M. Komura, T. Iyoda, Macromolecules 2007, 40, 4106. [27] T. Yamamoto, T. Kimura, M. Komura, Y. Suzuki, T. Iyoda, S. Asaoka, H. Nakanishi, Adv. Funct. Mater. 2011, 21, 918. [28] M. Komura, K. Watanabe, T. Iyoda, T. Yamada, H. Yoshida, Y. Iwasaki, Chem. Lett. 2009, 38, 408. [29] R. Watanabe, K. Kamata, T. Iyoda, J. Mater. Chem. 2008, 18, 5482. [30] X. Hou, Y. Liu, H. Dong, F. Yang, L. Li, L. Jiang, Adv. Mater. 2010, 22, 2440. [31] P. Müller-Buschbaum, Anal. Bioanal. Chem. 2003, 376, 3. [32] E. Metwalli, S. Couet, K. Schlage, R. Rohlsberger, V. Korstgens, M. Ruderer, W. Wang, G. Kaune, S. V. Roth, P. Muller-Buschbaum, Langmuir 2008, 24, 4265. [33] G. Renaud, R. Lazzari, F. Leroy, Surf. Sci. Rep. 2009, 64, 255. [34] G. Kaune, M. A. Ruderer, E. Metwalli, W. Wang, S. Couet, K. Schlage, R. Röhlsberger, S. V. Roth, P. Müller-Buschbaum, ACS Appl. Mater. Interfaces 2008, 1, 353. [35] D. Constantin, Z. S. Siwy, Phys. Rev. E. 2007, 76, 41202. [36] T. Kimura, Preparation of Free-Standing Micro-Phase Separated Film with Perpendicularly Penetrated Cylinder Structure, Tokyo Institute of Technology, Japan 2011.



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