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Honorary Editor General ZHOU GuangZhao (Zhou Guang Zhao) Editor General ZHU ZuoYan Institute of Hydrobiology, CAS, Editor-in-Chief LI LeMin , China Associate Editor-in-Chief CAO Yong South China University of Technology, China TIAN ZhongQun Xiamen University, China CHEN HongYuan University, China XUE Zi-Ling University of Tennessee, USA FENG ShouHua , China YUAN Quan Dalian Institute of Chemical Physics, CAS, China LIN GuoQiang Shanghai Institute of Organic Chemistry, CAS, China Members

BAO XinHe LIAN TianQuan XIONG RenGen Dalian Institute of Chemical Physics, CAS, China Emory University, USA South East University, China BU XianHe LIANG WenPing XU ChunMing Nankai University, China National Natural Science Foundation of China, China University of Petroleum, China CHAI ZhiFang China YAM Vivian Wing-Wah Institute of High Energy Physics, CAS, China LIN JianHua University of Hong Kong, China CHAN Albert S C Peking University, China YAN DeYue Hong Kong Polytechnic University, China LIU GuoJun Shanghai Jiao Tong University, China CHEN Xian Queen’s University, Canada YANG Bai University of North Carolina-Chapel Hill, USA LIU Jun O Jilin University, China CHEN XiaoMing Johns Hopkins Medicine Institute, USA YANG DongSheng Sun Yat-Sen University, China LU FengCai University of Kentucky, USA Institute of Chemistry, CAS, China CHEN Yi YANG PengYuan Institute of Chemistry, CAS, China NIE ShuMing Fudan University, China CUI ZhanFeng Georgia Institute of Technology and Emory University, USA YANG WeiTao Oxford University, UK Duke University, USA PAN CaiYuan DUAN Xue YANG XueMing Beijing University of Chemical Technology, China University of Science and Technology of China, China Dalian Institute of Chemical Physics, CAS, China FEI WeiYang YANG YuLiang , China PU Lin University of Virginia, USA Fudan University, China FENG XiaoMing QIAO JinLiang YAO ShouZhuo Sichuan University, China SINOPEC Beijing Research Institute of Chemical University, China GAO ChangYou Industry, China YAO ZhuJun Zhejiang Universtiy, China SHAO YuanHua Shanghai Institute of Organic Chemistry, CAS, GAO Song Peking University, China China Peking University, China SHEN ZhiQuan YOU XiaoZeng GUO ZiJian Zhejiang University, China , China Nanjing University, China SHUAI ZhiGang YU LuPing HAN BuXing Tsinghua University, China University of Chicago, USA Institute of Chemistry, CAS, China SUN LiCheng ZHANG HongJie HE MingYuan Royal Institute of Technology (KTH), Sweden Changchun Institute of Applied Chemistry, CAS, Research Institute of Petroleum Processing, TANG Ben Zhong China SINOPEC, China Hong Kong University of Science & Technology, ZHANG JinSong HONG MaoChun China University of California, Riverside, USA Fujian Institute of Research on the Structure of TIAN He ZHANG JinZhong Matter, CAS, China East China University of Science & Technology, University of California, Santa Cruz, USA China HUANG PeiQiang ZHANG John ZengHui Xiamen University, China TONG Liang New York University, USA HUANG Zhen Columbia University, USA Georgia State University，USA TUNG ChenHo ZHANG LiHe Technical Institute of Physics and Chemistry, CAS, Peking University, China JIANG GuiBin China ZHANG Xi Research Center for Eco-Environmental Sciences, WAN LiJun Tsinghua University, China CAS, China Institute of Chemistry, CAS, China ZHANG YuKui JIANG Long WANG MeiXiang Dalian Institute of Chemical Physics, CAS, China Institute of Chemistry, CAS, China Institute of Chemistry, CAS, China ZHAO XinSheng JIAO Kui WANG ShiQing Peking University, China Qingdao University of Science and Technology, University of Akron, USA China WANG ZhenGang Xiamen University, China JU HuangXian California Institute of Technology, USA ZHENG LanSun Nanjing University, China WANG ZhongLin Xiamen University, China KONG Wei Georgia Institute of Technology, USA ZHOU QiLin Oregon State University, USA WU YunDong Nankai University, China LI QianShu Hong Kong University of Scence & Technology, ZHU Tong South China National University, China China Peking University, China LI YaDong XIE ZuoWei ZHU Julian X Tsinghua University, China Chinese University of Hong Kong, China Université de Montréal, Canada

Editorial Staff ZHU XiaoWen (Director) SONG GuanQun ZHANG XueMei

SCIENCE CHINA Chemistry

Contents Vol.55 No.5 May 2012

SPECIAL ISSUE: In Honor of the 80th Birthday of Professor WANG Fosong Preface CHENG Stephen Z. D. & CAO Yong Sci China Chem, 2012, 55(5): 643–645

NEWS & COMMENTS

Professor Fosong Wang on his 80th birthday: A great scientist and a great ambassador SAWAMOTO Mitsuo Sci China Chem, 2012, 55(5): 647

FEATURE ARTICLES

Design and synthesis of self-healing polymers ZHANG MingQiu & RONG MinZhi Sci China Chem, 2012, 55(5): 648–676

New D--A dyes for efficient dye-sensitized solar cells QU SanYin, HUA JianLi & TIAN He Sci China Chem, 2012, 55(5): 677–697

Microstructure, morphology, crystallization and rheological behavior of impact polypropylene copolymer SHANG-GUAN YongGang, CHEN Feng & ZHENG Qiang Sci China Chem, 2012, 55(5): 698–712

© Science China Press and Springer-Verlag Berlin Heidelberg 2012 chem.scichina.com www.springerlink.com

ii

The abnormal behavior of polymers glass transition temperature increase and its mechanism WANG Xiang, QI GuiCun, ZHANG XiaoHong, GAO JianMing, LI BingHai, SONG ZhiHai & QIAO JinLiang Sci China Chem, 2012, 55(5): 713–717

REVIEWS

Recent advances in flexible and stretchable electronics, sensors and power sources TOK Jeffrey B.-H. & BAO Zhenan Sci China Chem, 2012, 55(5): 718–725

Polystyrene-based blend nanorods with gradient composition distribution WU Hui, SU ZhaoHui, TERAYAMA Yuki & TAKAHARA Atsushi Sci China Chem, 2012, 55(5): 726–734

Self-assembled structures of a semi-rigid polyanion in aqueous solutions and hydrogels SUN TaoLin, WU ZiLiang & GONG JianPing Sci China Chem, 2012, 55(5): 735–742

iii

ARTICLES

Large open-circuit voltage polymer solar cells by poly(3-hexylthiophene) with multi-adducts fullerenes GONG Xiong, YU TianZhi, CAO Yong & HEEGER Alan J. Sci China Chem, 2012, 55(5): 743–748

Polymer solar cells with an inverted device configuration using polyhedral oligomeric silsesquioxane-[60]fullerene dyad as a novel electron acceptor ZHANG Wen-Bin, TU YingFeng, SUN Hao-Jan, YUE Kan, GONG Xiong & CHENG Stephen Z. D. Sci China Chem, 2012, 55(5): 749–754

Inverted polymer solar cells with a solution-processed zinc oxide thin film as an electron collection layer YANG TingBin, QIN DongHuan, LAN LinFeng, HUANG WenBo, GONG Xiong, PENG JunBiao & CAO Yong Sci China Chem, 2012, 55(5): 755–759

iv

A structurally ordered thiophene-thiazole copolymer for organic thin-film transistors CHEN DuGang, ZHAO Yan, ZHONG Cheng, YU Gui, LIU YunQi & QIN JinGui Sci China Chem, 2012, 55(5): 760–765

Alkali metal salts doped pluronic block polymers as electron injection/transport layers for high performance polymer light-emitting diodes ZHANG Kai, LIU ShengJian, GUAN Xing, DUAN ChunHui, ZHANG Jie, ZHONG ChengMei, WANG Lei, HUANG Fei & CAO Yong Sci China Chem, 2012, 55(5): 766–771

Preparation and self-assembly of amphiphilic polymer with aggregation-induced emission characteristics QIN AnJun, ZHANG Ya, HAN Ning, MEI Ju, SUN JingZhi, FAN WeiMin & TANG Ben Zhong Sci China Chem, 2012, 55(5): 772–778

Shear and extensional rheology of entangled polymer melts: Similarities and differences SUN Hao & WANG Shi-Qing Sci China Chem, 2012, 55(5): 779–786

v

Energetics of dioxygen binding into graphene patches with various sizes and shapes YUMURA Takashi, KOBAYASHI Hisayoshi & YAMABE Tokio Sci China Chem, 2012, 55(5): 787–795

Theoretical study of current-voltage characteristics of carbon nanotube wire functionalized with hydrogen atoms FUENO Hiroyuki, KOBAYASHI Yoshikazu & TANAKA Kazuyoshi Sci China Chem, 2012, 55(5): 796–801

Tuning periodicity of polymer-decorated carbon nanotubes WANG WenDa, LAIRD Eric D., LI Bing, LI LingYu & LI Christopher Y. Sci China Chem, 2012, 55(5): 802–807

Electrical conductivities of carbon nanotube-filled polycarbonate/polyester blends XIONG ZhuoYue, SUN Yao, WANG Li, GUO ZhaoXia & YU Jian Sci China Chem, 2012, 55(5): 808–813

vi

Comparison of magnetic properties of DNA-cetyltrimethyl ammonium complex with those of natural DNA KWON Young-Wan, CHOI Dong Hoon, JIN Jung-Il, LEE Chang Hoon, KOH Eui Kwan & GROTE James G. Sci China Chem, 2012, 55(5): 814–821

TEMPO-substituted polyacrylamide for an aqueous electrolyte-typed and organic-based rechargeable device CHIKUSHI Natsuru, YAMADA Hiroshi, OYAIZU Kenichi & NISHIDE Hiroyuki Sci China Chem, 2012, 55(5): 822–829

Oxidative polymerization of hydroquinone using deoxycholic acid supramolecular template ZHANG AiJuan, HE Jian, GUAN Ying, LI ZhanYong, ZHANG YongJun & ZHU Julian X. Sci China Chem, 2012, 55(5): 830–835

Electrochemically sensitive supra-crosslink and its corresponding hydrogel DU Ping, CHEN GuoSong & JIANG Ming Sci China Chem, 2012, 55(5): 836–843

vii

Exploration of structure and mechanism of insoluble gels formed in microwave-assisted Suzuki coupling for poly(9,9-dihexylfluorene)s ZHANG WenSi, LU Ping, WANG ZhiMing & MA YuGuang Sci China Chem, 2012, 55(5): 844–849

Improvement of the physical properties of poly(methyl methacrylate) by copolymerization with N-pentafluorophenyl maleimide; zero-orientational and photoelastic birefringence polymers with high glass transition temperatures TAGAYA Akihiro, LOU LiPing, IDE Yoko, KOIKE Yasuhiro & OKAMOTO Yoshiyuki Sci China Chem, 2012, 55(5): 850–853

Chemical-physical aspects of formation and evolution of phase structure in multi-polymers: Intensity fluctuation, phase structure and its fractal characteristics in blends of isotactic polypropylene with poly(cis-1,4-butadiene) rubber MA GuiQiu, YANG YuPing, HUANG DingHai & SHENG Jing Sci China Chem, 2012, 55(5): 854–864

SCIENCE CHINA Chemistry

• ARTICLES • May 2012 Vol.55 No.5: 802–807 · SPECIAL ISSUE · In Honor of the 80th Birthday of Professor WANG Fosong doi: 10.1007/s11426-012-4502-4

Tuning periodicity of polymer-decorated carbon nanotubes

WANG WenDa, LAIRD Eric D., LI Bing, LI LingYu & LI Christopher Y.*

A. J. Drexel Nanotechnology Institute and Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104, USA

Received October 1, 2011; accepted November 23, 2011; published online February 2, 2012

Carbon nanotube (CNT) is one of the most extensively investigated nanomaterials. Patterning soft matter such as liquid crys- tals and polymers on CNTs could potentially enable various applications for CNTs. We have demonstrated that controlled polymer crystallization using CNTs as the 1D nucleation sites can lead to periodically functionalized CNTs. Here we show that selected crystalline block copolymers can be periodically decorated along CNTs. This facile technique opens a gateway to pe- riodic patterning on 1-D nanomaterials.

polymer crystallization, carbon nanotube, block copolymers

1 Introduction [20–22]. Polymer crystallization has been recently used to probe polymer/nanoparticle interface [23–32]. In order to clearly Functionalization of carbon nanotubes (CNTs) is of great reveal the CNT/polymer interface and periodically pattern interest from both scientific and technological viewpoints crystalline polymers on CNTs, we proposed to use a con- [1–3]. Periodically functionalized CNTs can directly lead to trolled solution crystallization method. Polymer single crys- controlled two-dimensional or three-dimensional CNT su- tal-functionalized CNTs were recently observed [23, 33–40]. prastructures, which is an essential step toward building This novel technique is a generic method for CNT and nan- future CNT-based nanodevices. Very few reports have ad- ofiber functionalization [41, 42]. It can be used for a variety dressed periodic functionalization/patterning on CNTs. of CNTs, including single-walled (SWNT), multi-walled Czerw et al. demonstrated regular organization of poly (MWNT) and vapor grown carbon nanofibers (CNF). For- (propionylethylenimine-co-ethylenimine) on CNTs using mation mechanism of this unique structure was attributed to Scanning Tunneling Microscopy (STM) [4]. Single-stranded “size-dependent soft epitaxy”. Two main factors affected DNAs have been bound to CNTs, resulting in periodic heli- the polymer chain orientation on CNT during crystal growth: cal wrapping on the surface of CNTs [5, 6]. Surfactants epitaxy and geometry confinement. As the diameter of the such as sodium dodecyl sulfate (SDS) have been found to CNT is comparable to the radius of gyration of a polymer form uniform patterns on CNTs [7]. On the other hand, chain, its highly curved surface leads to strong geometric CNT-induced polymer crystallization is studied in polymer confinement and polymer chains are forced to align parallel CNT nanocomposites (PCNs) formed by CNTs and semi- to the CNT surface upon crystallization, regardless of the crystalline polymers such as iPP [8–12], PE [13], polyvinyl CNT chirality. As the diameter increases to ~100–300 nm, alcohol (PVA) [14], polyacrylonitrile (PAN) [15–17], ther- the geometric confinement effect became weakened and moplastic polyimide [18], conjugated organic polymer [19], epitaxy dictated the polymer lamellar growth. as well as thermoplastic elastomers such as polyurethane We have also demonstrated that the periodic structure is largely due to density fluctuation of polymer concentration *Corresponding author (email: [email protected]) along the CNT surface during the crystallization process;

© Science China Press and Springer-Verlag Berlin Heidelberg 2012 chem.scichina.com www.springerlink.com Wang WD, et al. Sci China Chem May (2012) Vol.55 No.5 803 the pattern therefore is not quite regular. To this end, using (FTIR) spectra were obtained on the Varian Excalibur semicrystalline block copolymers (BCP) could lead to uni- FTS-3000. Vacuum evaporation of carbon was conducted form patterns [43, 44]. The research work involving both on a Polaron Range E6300 Vacuum Evaporator. BCP and CNTs has been reported by a few groups [45–50]. For example, Taton and his coworkers used BCP polysty- 2.3 Fractionation of PE-b-PEO rene-block-poly(acrylic acid) (PS-b-PAA) to form micelles in H2O/ dimethylformamide solution [47]. SWNT was en- 10 g of PE-b-PEO was dissolved in 50 mL of dichloro- capsulated in core of the micelles made of PS while PAA methane. 100 mL of isopropyl ether was added to the solu- can be further cross-linked to form a solid structure. The tion subsequently. The mixture was then placed in a vacuum similar concept was adopted later on by Park et al. [49], and chamber to gradually remove the solvents. The BCPs with Agarwal et al. [46]. Most recently, we demonstrated that the highest PE percentage precipitated out first. The precip- low molecular weight polyethylene-b-poly (ethylene oxide) itated BCP was collected and labeled as fraction 1 to 6 in a (PE-b-PEO) BCP could be patterned onto CNT surface [39]. time order. Fraction 4 was chosen to be used in this research. Herein we report that polymer crystallization induced phase The GPC spectrum shows that the PDI of the fractionated separation holds the key to this regular pattern formation. BCP is 1.15. From the end-group analysis using 1H NMR, This unique hybrid structure is promising for a variety of the molecular weight is 1700 g/mol and the PE block is 50 nanoelectronic and biomedical applications. wt%.

2 Experimental 2.4 Thin film crystallization of BCP on SWNTs 0.02 mg of SWNTs was dissolved in 1.0 g of DCB by 1 h 2.1 Materials sonication. The SWNT/ DCB solution was dropcast on the Purified HiPco SWNTs were purchased from Carbon Nan- carbon-coated nickel grids and dried at ambient temperature. otechnologies Inc. 1,2-Dichlorobenzene (DCB), pentyl ace- BCP/chloroform solution with various concentrations was tate, thioglycolic acid, sulfuric acid (98%), isopropyl ether, spincoated on the SWNT-loaded grids at 3000 r/min for 30 dichloromethane, toluene and chloroform were purchased s. The samples were stained by ruthenium tetroxide (RuO4) from Sigma-Aldrich and used as received. PE-b-PEO (mo- prior to the TEM observation. lecular weight 1,400 g/mol, 50 wt% PE) was purchased from Sigma-Aldrich and was fractionated before usage. 2.5 Solution crystallization Polybutadiene (1,4 rich)-b-poly (ethylene oxide) (PB-b-PEO) (molecular weight 930–1020 g/mol) was purchased from For polymer solution crystallization, DCB was used as sol- Polymer Source Inc. and used as received. PE-b-SBR block vent. 0.1–0.5 mg PE-b-SBR was dissolved in 4 g DCB at copolymer samples were kindly provided by Bridgstonetire 120 °C. 0.1 mg SWNT and 1 g DCB solution was sonicated Co. PE block synthesized by hydrogenation of polybutadi- for 2–3 h at 45 C and then added to PE/ DCB solution. The ene (PB) has average molecular weight (MW) of 25,200, mixture was then quenched to the preset crystallization polydispersity index (PDI) of 1.14 and SBR has MW of temperature (Tc = 88 °C). The crystallization time was con- 100,220 and PDI of 1.25. The total hydrogenation percent- trolled to be 0.5–3 h. Sample was isothermally filtered after age is 99.3%. crystallization to remove the uncrystallized materials.

2.2 Instruments 3 Results and discussion

The Branso Ultrasonic Cleaner was used for sonication. 3.1 Homopolymer decorated CNTs Spincoating was performed on the Specialty Coating Sys- tems Spin Coater-G3P12. The Fisher Scientific Centrifuge Figure 1 shows an unshadowed TEM image of PE single Marathon 21000 was used for centrifugation. TEM experi- crystal decorated SWNT. Edge-on PE crystals can be clear- ments were conducted on the JEOL 2000FX TEM with an ly seen from the image. Selective area electron diffraction accelerating voltage of 120 kV. The PDI of PE-b-PEO was (ED) pattern from the circled area is shown in Figure 1(b). characterized by gel permeation chromatography (GPC) at While it is relatively weak, a pair of (002) diffraction spots 40 °C using tetrahydrofuran as the eluent at a flow rate of can be seen and the orientation is parallel to the lamellar 1.0 mL/min. Data were collected by the Refractive Index normal (CNT axis). This confirms that PE crystals are Detector 2414 and analyzed using the software provided by formed by CNT-induced PE crystallization and the polymer Waters. The calibration curve was constructed with nar- chains are parallel to the CNT axis. Figure 1(c) shows the rowly distributed PEO standards. Proton nuclear magnetic schematic representation of the unique hybrid structure. resonance (1H NMR) was measured on the Unityinova 500 This fibril-linked-disc structure is similar to the classic MHz NMR Spectrometer. The Fourier Transform Infrared “shish-kebab” polymer crystals formed under shear field, as 804 Wang WD, et al. Sci China Chem May (2012) Vol.55 No.5 first observed in the 1960s by Pennings [51, 52]. A shish- kebab polymer crystal usually consists of a central fibril (shish) and disc-shaped folded-chain lamellae (kebab) ori- ented perpendicularly to the shish. Since the morphology is similar to the classical polymer shish kebabs, nano hybrid shish kebab (NHSK) is used to describe the structure. High resolution TEM (HRTEM) was used to reveal the fine structure on the surface of SWNTs. Figure 2 shows a HRTEM image of SWNT/PE NHSK structure. At the PE kebab vicinity area (~2–5 nm from PE kebab) there are some polymer-like coatings on SWNT surface possibly due to the dangling chains or chain ends extended from PE sin- Figure 3 TEM image of PE-b-PEO decorated SWNTs. gle crystal kebab. Note that in this case, there are bundles of SWNTs, instead of individual SWNTs, that form the shish structure. This is because that before PE crystallization, TEM image of the resultant BCP/SWNT hybrid. Note that SWNTs are not completely “dissolved” so that these bun- the sample is stained with RuO4 to enhance the contrast. In dled SWNTs are wrapped by PE lamellar crystals. the image there are numerous elongated “worm-like” struc- tures with dark and bright stripes. The average length is ~1 3.2 Thin film crystallization of BCP on SWNTs m and the width is ~50 nm. The dark regions are PEO, while the bright ones are PE blocks because PEO was selec- Thin film crystallization was first used to explore the feasi- tively stained by RuO4. The consistent orientations of the bility of CNT-induced BCP crystallization. A SWNT/DCB adjacent stripes and the aspect ratio of this unique solution was dropcast on a carbon-coated nickel grid and worm-like morphology indicate that the axis of the under- dried at ambient temperature. The fractionated PE-b-PEO neath SWNT is perpendicular to the stripes, as shown in was dissolved in chloroform and the solution was then Figure 1(b). spincoated onto the SWNT-loaded grid. Figure 3 shows a Observing this regular pattern on CNTs at ~12 nm scale is intriguing and the formation of this unique structure is related to the interplay between BCP phase separation and CNT-induced polymer crystallization. BCPs are known to be able to phase separate into ordered microstructures at ~10–100 nm scale [53–55]. As they are dissolved in sol- vents, BCPs can be considered as macromolecular surfac- tants [47, 56]. In a CNT/BCP system, if one segment of the BCP is crystalline and is able to form single crystals on Figure 1 TEM micrograph of SWNTs periodically patterned with PE CNTs, the BCP phase separation and the CNT-induced lamellae crystals produced by crystallization of PE on SWNTs at 88 °C in crystallization should affect each other. Depending on the DCB (a); (b) the corresponding ED pattern; (c) the schematics of a NHSK. BCP/CNT/solvent interaction parameters, a few scenarios are possible: (1) BCPs form micelles (or other aggregates), which separate from CNTs; (2) BCPs form micelles wrap- ping around CNTs; and (3) one segment of the BCP crystal- lizes on CNTs, leading to the CNT-induced BCP phase sep- aration. The morphology of the BCP/SWNT hybrid in Figure 2 clearly indicates that the phase separation of PE-b-PEO is directed by the underneath SWNTs, suggesting that scenario 3 is the dominant physical process in the present system. In order to demonstrate the role of PE crystallization in the formation of the present hybrid structures, we further con- ducted two control experiments. In the first control experi- ment, PE-b-PEO was replaced with PB-b-PEO. In the se- cond one, a thin layer of amorphous carbon was deposited onto the SWNTs prior to spincoating. In both cases, alter- nating BCP patterns were not observed on the SWNTs. These control experiments clearly demonstrated that

CNT-induced PE crystallization was critical to the for- Figure 2 HRTEM micrograph of PE decorated SWNTs. mation of the alternating patterns on the CNTs. In the present Wang WD, et al. Sci China Chem May (2012) Vol.55 No.5 805

BCP/SWNT hybrids, upon crystallization, PE chains aligned which wrap on SWNT surface in between PE strips. These parallel to the SWNT axis forming the bright stripes. The are loosely packed amorphous SBR block. observed alternating stripes are thus perpendicular to the On the basis of the above observations, we propose a SWNT axis. Compared with the crystal patterns formed in growth mechanism for the formation of the BCP-decorated the CNT-induced homopolymer crystallization, the present SWNTs. During spincoating, the BCP molecules randomly alternating pattern formed by the BCP is far more uniform. adsorb onto the SWNT surface due to the favorable interac- In Figure 3, the period of the alternating pattern is 11.9 ± tion between PE segments and SWNTs, leading to hetero- 0.9 nm. The width of the bright stripes along the CNT axes geneous nucleation. After a stable nucleus forms, the PE is 5.9 ± 0.7 nm. Comparing this number with the extended crystal starts to grow following the soft epitaxy mechanism chain length of the PE block suggests that each PE domain [23]. In the solution crystallization case, PE crystallizes into is made of one layer of interdigitated extended PE chains. lamellar single crystal in solution and SBR blocks are ex- cluded out of the order structure as defects. So SBR dangles 3.3 Crystallization of PE-b-SBR on SWNTs either on the top or bottom of the PE lamellar in solution state. Upon solvent evaporation, SBR blocks adhere on PE-b-SBR was also used to crystallize onto SWNTs. De- SWNT surface because of reduced surface energy. Figure 5 tailed information regarding PE-b-SBR can be found in the shows a schematic representation of BCP decorated experimental section. Solution crystallization was used and SWNTs. DCB was the model solvent. Figure 4 shows TEM images of PE-b-SBR/SWNT nanostructure. Samples in Figure 4(a) was shadowed with platinum/palladium alloy wire (80:20, 0.2 mm) to enhance the contrast. The red arrow in Figure 4(a) indicates the shadow direction. It can be seen that there are lamellar-like objects on the surface of SWNT. These objects are arranged in an orthogonal orientation with re- spect to the tube axis. These lamellar-like objects are PE-b-SBR single crystals grown in DCB solution and they seem to be rounded in shape. The lateral size of these crystals is ~25 nm and the dis- tance between adjacent crystals is ~25–30 nm. Although shadow greatly enhanced the contrast of image, the sample appears “fatter” than its true thickness. Staining was also a widely used technique to reveal the fine structure of poly- mer and biological specimen. RuO4 was used to stain the sample. Figure 4(b) shows a TEM image of stained Figure 5 Schematic illustration of PE-b-SBR functionalized SWNT PE-b-SBR functionalized SWNT sample. TEM grid con- structure. taining the sample was stained in RuO4 vapor for 15 min before imaging. It is clear that the PE-b-SBR crystals appear much thinner than those in shadowed image. The darker 4 Conclusions strips indicated by blue arrows in Figure 4(b) are PE block. There are some appealingly lighter and foggy materials We have produced nanoscale alternating patterns of BCP along SWNTs. Both PE-b-PEO and PE-b-SBR have been used to form regular and periodic patterns on SWNTs. The periodicity of the patterns was ~12–30 nm along the SWNT axis. The formation mechanism was attributed to the inter- play of CNT-induced PE crystallization and the BCP phase separation. The reported work demonstrated a facile method to achieve periodic patterning on SWNTs, a key step to- wards using 1-D nanomaterials for the nanodevice applica- tions.

This work was supported by the National Natural Science Foundation of Figure 4 TEM images of PE-b-SBR functionalized SWNTs produced by China (DMR-0804838). crystallization of PE-b-SBR on SWNTs at 88 °C in DCB for 0.5 h. (a)

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