Nanostructures

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J. Phys. Chem. B 2007, 111, 3918-3926

Fabrication of Shape-Controllable Polyaniline Micro/Nanostructures on Organic Polymer Surfaces: Obtaining Spherical Particles, Wires, and Ribbons Wenbin Zhong, Yongxin Wang, Yan Yan, Yufeng Sun, Jianping Deng, and Wantai Yang* State Key Laboratory of Chemical Resource Engineering, Beijing UniVersity of Chemical Technology, Beijing 100029, People’s Republic of China, and Department of Polymer Science, Beijing UniVersity of Chemical Technology, Beijing, 100029, People’s Republic of China ReceiVed: NoVember 25, 2006; In Final Form: February 3, 2007

A novel strategy was developed in order to prepare various micro/nanostructured polyanilines (PANI) on polymer substrates. The strategy involved two main steps, i.e., a grafting polymerization of acrylate acid (AA) onto the surface of a polypropylene (PP) film and subsequently an oxidative polymerization of aniline on the grafted surface. By tuning the conformation of the surface-grafted poly acrylate acid (PAA) brushes, as well as the ratio of AA to aniline, the shape of the PANIs fixated onto the surfaces of the polymer substrate could be controlled to go from spherical particles to nanowires and eventually to nanoribbons. In these structures, the PAA brushes not only acted as templates but also as dopants of PANI, and thereby, the nanostructured PANIs could be strongly bonded with the substrate. In addition, the surface of the PP films grafted with polyaniline nanowires and nanoribbons displayed superhydrophobicity with contact angles for water of approxiamtely 145 and 151°, respectively.

Introduction The fabrication of nanostructured polyanilines (PANIs) has become one of the most important domains in current research, mainly due to their potential applications in nano/microelectronic devices,1 nanoactuators,2 sensors,3 etc. Numerous micro/nanostructured PANIs with varying morphologies, including nanoparticles,4 nanowires,5 nanotubes,6 dendrites,7 helical/chiral nanofibers,8 hollow spheres/cubes,9 filaments,10 etc., have been synthesized with various methods. Recently, PANI nanowires have been prepared through an interfacial and “seeding” polymerization,11 and the synthesis of micro/nanostructured PANIs with a “soft template” such as poly acrylate acid (PAA) has also been reported.8a,12 For applications of nanostructured devices, a more interesting issue is how to construct these PANI nanostructures on substrate surfaces. To the best of our knowledge, most reports have focused on the fabrication of nanostructured PANIs on the surfaces of inorganic materials,13 whereas relevant research with respect to organic polymer substrates is quite limited.14,15 The use of organic polymer substrates is, however, increasing in importance owing to their light weight, flexibility, insulating ability, shock resistance, and low cost.16 Unfortunately, the direct preparation of nanostructured PANIs on organic surfaces by current aqueous oxidative or electrochemical synthesis methods is difficult because of the inertness and insulating properties of the surfaces. To realize this goal, at least two problems need to be solved: how to strongly immobilize the nanostructured PANIs onto the substrate surface and how to control the growth of the PANIs according to predefined shapes and directions. The surface wettability is an important property for most solid materials and is defined by both the surface free energy and surface morphology. Much attention has been focused on * To whom correspondence should be addressed. E-mail: yangwt@ mail.buct.edu.cn.

constructing superhydrophobic (with water contact angles (CA) larger than 150°) or superhydrophilic (with CAs lower than 5°) material surfaces, both for the sake of fundamental research and practical applications.17 The wettability of PANIs and polypyrrole (PPy) has been studied, and it has been found that the CA of PPy was increased from 12 to 96° after being doped with various amounts of fluorinated counterions.18 The reversible conversion of a PPy film from being superhydrophobic to becoming superhydrophilic was realized by changing the electrical potential.19 Recently, the fabrication of superhydrophilic PPy nanowire networks has been carried out.20 As for PANI, it has been reported that its wettability can be controlled by the redox degree21 and that the change in wettability from hydrophilic to hydrophobic can be controlled by the deposition time.22 Additionally, a PANI/polystyrene composite with superhydrophobicity has been prepared via an electrospinning method.23 In a previous study, where the motivation was to develop an efficient method for fabricating stable and morphologycontrolled PANI mico/nanostructures on flexible and insulating polymeric substrates, two primary results were achieved: (1) Conductive composite films with surface morphologies consisting of irregular particles were obtained when films of polypropylene photografted with acrylic acid (PP-g-PAA) were placed in aqueous solutions of aniline (ANI)/HCl/(NH4)2S2O8.14 (2) The surface morphology of these PP-g-PAA films displayed submicro/nanostructured PANI dendrites and a superhydrophilic surface performance after substitution of HCl with PAA and sodium dodecyl sulfate (SDS).15 In the present investigation, we report on a novel fabrication route for obtaining PANI micro/nanostructures on PP-g-PAA. This fabrication route is depicted in Figure 1 and consists in using the same PP-g-PAA film as previously described and simply adding AA monomer to the reaction solution instead of PAA. Subsequently, the ratio of AA to aniline was controlled by conducting a routine aqueous oxidative polymerization. Thus,

10.1021/jp0678296 CCC: $37.00 © 2007 American Chemical Society Published on Web 03/28/2007

Fabrication of Polyaniline Micro/Nanostructures

J. Phys. Chem. B, Vol. 111, No. 15, 2007 3919

Figure 1. An illustration of the fabrication method for PANI micro/nanostructures on the surface of PP films: (a) spherical particles, (b) nanowires, and (c) nanoribbons.

spherical particles, wires, and ribbons of PANI tethered to the surface of the PP film could be reproducibly obtained. Furthermore, since the PAA brushes acted as dopants for PANI, these PANI nanostructures were strongly bonded with the substrate. The resulting surface of the PP films with PANI nanowires and nanoribbons showed a high hydrophobicity. Experimental Details Materials. Commercially cast poly(propylene) (PP) films with 30 µm thicknesses were cut into rectangular samples with typical dimensions of 3.0 cm × 5.0 cm and were then extracted by acetone for 36 h to remove impurities and additives before use. Aniline and acrylic acid (AA) were distilled under a reduced pressure. Acetone, ammonium persulfate (APS), benzophenone (BP), and methanol were all of analytical grade and used without further purification. Preparation of Micro/Nanostructured PANIs on PP Film Surfaces. The method for preparing nanostructured PP-g-PAA/ PANI films involved two main steps, i.e., the grafting of PP films with AA followed by an oxidative polymerization of aniline monomer on the surface of these PP-g-PAA films. In a typical experiment, the grafting of PAA on the PP film surface was carried out with the photoinitiator BP, after which the films were purified, as reported by Yang and co-workers.24 Subsequently, the PP-g-PAA film (with an approximate grafting percentage of 1.1% PAA) was fixed to the wall of a beaker, in which 300 mL of deionized water with 2.3 mL of AA and various amounts of aniline were added. APS (with a molar ratio to aniline of 1:1) was charged to the above solution, which was then stirred for 2 h in an ice bath. The reaction was allowed to proceed for 12 h in the ice bath. Finally, the composite film was rinsed with water and then washed thrice with deionized water and methanol, consecutively, followed by drying in a vacuum oven at 30 °C for 24 h. Characterization. Atomic force microscopy (AFM) (Nanoscope III, Digital Instruments), field emission scanning electron microscopy (FESEM, JEOL JSM-6700 F), and scanning electron microscopy (SEM) (S250HK3, Cambridge) were used to observe the surface features of the resulting films. The electrical conductivity was measured by a two-probe method under laboratory conditions with a 2400 digital source meter (Keithley). The distributions of grafted chains on the surfaces of PP-g-PAA and PP-g-PAA/PANI films were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The ATR-FTIR spectra were recorded on Nicolet NEXUS 670 equipped with a variable angle horizontal ATR accessory, on which a 45° rectangular ZnSe crystal was used. Water CAs were detected by a contact angle system

(OCA20, Dataphysics). The UV-vis spectra of the PP-g-PAA/ PANI films were recorded on a GBC CINTRA 20. Results and Discussion When the molar ratio of AA to aniline was between 1:0.3 and 1:0.6, monolayer of spherical PANI particles was formed on the surface of the PP film (Figures 2). The FESEM images confirmed that the spherical particles were immobilized on the surface. The diameters of the spheres were between 70 and 200 nm (parts a and b of Figure 2) for a molar ratio of AA to aniline of 1:0.3, whereas they were in the range of 700 to 1100 nm (parts c and d of Figure 2) for a ratio of 1:0.6. It is reasonable to deduce that the average diameter of these particles could be readily controlled by tuning the ratio of AA to aniline. In addition, from parts e and f of Figure 2, it was clear that the number of spherical PANI particles increased with an increasing grafting percentage of PAA. It was found from wettability measurements that the CA values of PP films tethered with PANI spheres were 61 and 94°, corresponding to particle diameters of 70-200 and 700-1100 nm, respectively. In comparison it can be mentioned that the CAs of an untreated PP film and a PP-PAA film were 102 and 41°, respectivly.15 These results led to the logical suggestion that the PANI spheres were immobilized on the surface of the PP film through the grafting of PAA. Since PAA can be used as a template in order to fabricate nanostructured PANIs,8a,12,15,25 it was expected that PANI nanowires could be formed and immobilized on the surfaces of PP films through the grafted PAA. Figure 3 shows the morphology of such PANI nanowires on a PP film surface. Large-range porous PANI nanowires were observed by FESEM (Figure 3a) for molar ratios of AA to aniline between 1:0.9 and 1:1.1. High magnification (Figure 3b) of an area with a low PANI nanowire population displayed them laying horizontally on and growing from (Figure 3c) the PP film surface. In an area with a denser population, on the other hand, it was apparent from the high magnification FESEM image (Figure 3d) that the PANI nanowires were oriented perpendicularly to the surface as a result of crowding. The PANI nanowires were about 90140 nm in diameter and approximately 4 µm in length, as could be seen from the micrographs. There were slight increases in the average diameter between the samples when the molar ratio of AA to aniline was changed (i.e., 1:0.9 to 1:1.1). The slight difference in the length between the nanowires and PANI prepared with PAA/SDS15 can be correlated with the growth of the wires.13e,f,26 In addition, the formation of PANI nanowires was almost independent of the AA concentration in the current system (i.e., 0.07-0.3 M) and as long as the molar ratio of AA

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Figure 2. FESEM micrographs of PP film surfaces tethered with PANI spheres obtained from 0.11 M AA with a PAA grafting percentage of (a, b, c, d) 1.1%; (a and b) AA/aniline ) 1:0.3, (a) low magnification image, (b) high magnification image, CA image inset; (c and d,) AA/aniline ) 1:0.6; (c) low magnification image; (d) high magnification image, CA image inset; (e) AA/aniline ) 1:0.6, PAA grafting percentage of 0.8%; (f) AA/aniline ) 1:0.6, PAA grafting percentage of 1.5%.

to aniline was maintained between 1:0.9 to 1:1.1, the PANI nanowires could be readily obtained. However, for a molar ratio of AA to aniline of about 1:0.7, PANI spheres and nanowires were found to coexist. The aniline concentration was increased in the polymerization in order to further reveal the effect of the molar ratio of AA to aniline on the morphology of PANI. It was interesting to find that at a molar ratio of AA to aniline of 1:1.2 (AA, 0.23 M), PANI nanoribbons were formed on the surface of the PP films. Figure 4a shows a large-range image of the formed PANIs. It can be seen that they were somewhat irregularly dispersed on the surface. Figure 4b displays how the PANI nanoribbons aggregated together as “petals”, and among these “petals”, some of the PANI nanoribbons took roles as “linkers” (Figure 4c). The high magnification FESEM image (Figure 4d) clearly demonstrated that the dense area (in Figure 4a) was constructed by PANI nanoribbons. From parts b-d of Figure 4, the sizes of the nanoribbons could be approximated to 4 µm in length, 600 nm in width, and 70 nm in thickness. Moreover, compared to the straight nanowires observed in Figure 3, the PANI nanoribbons displayed a curved shape. At a molar ratio of AA

to aniline of 1:1.4, however, no nanoribbons were obtained. Instead microspheres and a few wires appeared on the PP film surface. ATR FTIR was employed to characterize the molecular structure of the spherical particles, nanowires and nanoribbons of PANI on the PP film surface. The spectra revealed that the characteristic peaks of the three PANI types were almost identical. Figure 5 displays one of these PP/PANI spectra along with control spectra of films of neat PP and PP-g-PAA. The PP/PANI spectrum displayed the three characteristic peaks of PANI, i.e., at 1301 cm-1 (CsN stretching vibration mode), 1497 cm-1 (CdC stretching vibration of benzenoid rings), and 1585 cm-1 (CdC stretching vibration of quinoid rings), as well as the characteristic band at 1708 cm-1 (CdO stretching vibration of carbonyl) suggesting that the PANI was doped with the carboxylic groups (COOH) of PAA. On the basis of previous work,28bit is reasonable that PAA as dopants should include two parts: one is PAA brushes (surface grafted chains), and the other is PAA oligomers attributed to AA polymerized by APS. These results corresponded well with what has already been reported in literature.12a,27



Figure 3. FESEM images of PANI nanowires on the surface of a PP film obtained with a PAA grafting percentage of 1.1%; an AA concentration of 0.11 M and an AA/aniline mol ratio of 1:1: (a) low-magnification image of PANI nanowires, CA image inset; (b) high-magnification image of PANI nanowires (low population area); (c) high-magnification image of PANI nanowires; (d) high-magnification image of PANI nanowires (dense population area).

Since the molar ratio of AA/aniline was found to control the PANI morphology (giving rise to either spherical particles, wires or ribbons), it was necessary to characterize the UV-vis spectra of the PP/ PANI composites (Figure 6). In Figure 6a, the PP/ PANI film with surface spherical particles displayed a strong peak at 330 nm, corresponding to the π-π* transition of benzene rings in PANI.28 However, this peak at 330 nm could not be seen for either the nanowires (Figure 6b) or the nanoribbons (Figure 6c). A broad peak with a tail at 800 nm assigned to the polaron transition (a typical protonation characterization) was found to slightly decrease with the concentration of aniline (Figure 6).29,12b,27 These results suggested that the PANI was doped with PAA. The conductivity of the PP/ PANI spheres, nanowires, and nanoribbons was 1.6 × 10-2, 8.3 × 10-2, and 5.7 × 10-2 S/cm, respectively, corresponding to molar ratios of AA to aniline of 1:0.6, 1:1, and 1:1.2. The reason for the conductivity of the PP/PANI spheres being slightly lower than for the other morphologies was probably a result of the spherical particles being dispersed. Moreover, the conductive performance of the PANI nanostructures further confirmed that they were doped with PAA. In a previous report,28b the investigation of the homopolymerization behavior of aniline in the present of AA was carried out. The following conclusions were drawn from this study: (1) The current system polymerized more slowly as compared to a system containing inorganic acid, and usually needed 4-10 h at 0 °C; (2) Free sulfate radicals produced from the decomposition of APS were able to initiate the polymerization of AA to form a PAA oligomer with a SO4H end group.28b Moreover, the change in pH value of the bulk solution was measured during the polymerization. The initial pH value was found to be 3.4, 3.7, 4.2, and 4.5 in the bulk solutions with the molar ratios of AA/aniline being 1:0.3, 1:0.6, 1:1, and 1:1.2, respectively. After the polymerization, the final pH values had

decreased to 3.1, 2.9, 2.1, and 1.9, respectively. When comparing these results with those from routine system containing inorganic acid, the changes in pH were unusual with three interesting aspects: (1) In the beginning of the polymerization, the values were high, corresponding to a low acidity; (2) At the end of the polymerization, the values were low, corresponding to a high acidity; (3) The higher the aniline concentration, the higher was the initial pH value, and the lower was the final pH value. Generally, low pH values favor polymerization.30 In order to further understand the mechanism of the formation of the PANI micro/nanostructures on the PP surface, the surface morphologies of PP films grafted with PAA, were investigated by AFM (parts a and b of Figure 7). It was apparent that the monolayer of spherical PAA particles with typical diameters of 30 nm were immobilized on the surface of the PP film. These results were similar to those of a PP film grafted with polymethyl methacrylate through a micro-emulsion system.31 As is known, the conformational variation of PAA polymer brushes from coil to extension in the solid-liquid interface depends on the environmental pH value and/or the content of carboxyl salt in the PAA chains.32 The molar ratio of AA (acid) to aniline (base) determines the ratio of aniline that should react with the carboxyl acid of the PAA brushes. It was expected that a higher concentration of the carboxyl-aniline salt would lead to an increased extension of the PAA brush in the solidliquid interface. Additionally, since PANI was a rigid macromolecule and PAA acted as a dopant, the conformation of PAA would also change under the effect of the PANI chains.7a When the molar ratio of AA to aniline was between 1:0.3 and 1:0.6, only small amounts of aniline were able to react with the PAA grafted on the PP film, as a result of AA being in excess. Therefore, the coil state of PAA could be maintained. Moreover, the degree of coiling of the PAA chains would probably decrease with an increasing concentration of aniline.


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Figure 4. FESEM images of PANI nanoribbons on the surface of PP film, obtained with a 1.1% grafting percentage of PAA, 0.23 M concentration of AA, and a molar ratio of AA/aniline of 1:1.2: (a) low-magnification image of the PANI nanoribbons, CA image inset; (b) high-magnification image of the PANI nanoribbons (like “petals”), (c and d) high-magnification images of the PANI nanoribbons in low populated and densely populated areas, respectively.

Figure 5. ATR FTIR absorbance spectra of (a) a PP film, (b) a PPg-PAA film, and (c) a PP/PANI nanowires composite film.

Figure 6. UV-vis spectra of conductive PP/PANI composite films obtained from an AA concentration of 0.11 M and AA/aniline molar ratios of (a) 1:0.6; (b) 1:1; (c) 1:1.2.

Thus, by adding APS to the aniline solution, the coiled PAA would give rise to the formation of size-controllable PANI spheres (Figure 2) on surfaces of polymer films. It should however be noted that the sizes of the PANI particles were much larger than the PAA ones. It was thus believed that a mechanism existed for the particle growth in the system. Such a scenario could be explained by the surface polymerization of anilines starting when the aniline monomers located on/in the PAA particles were reacted or adsorbed. This was followed by the polymerization taking place preferentially at the surface of the initial PANI particles according to a well-known auto-accelerated (self-activating) effect,33 i.e., the presence of PANI promoted the polymerization of aniline. Consequently, these

particles, immobilized on the surface of PP-g-PAA, would experience an increased growth. When the molar ratio of AA to aniline was in the range 1:0.9 to 1:1.1, more aniline monomers could access the PP-g-PAA surface. Thus the PAA chains would be able to extend out into the solution as a result of the formation of carboxyl-aniline salt. However, these PAA chains with carboxyl-aniline salt groups still had a tendency to aggregate and the assembly acted as the initial growth template for PANI. In order to explore the growth mechanism of the PANI wires, we observed the morphology of the PANIs 30 min after the addition of APS for a molar ratio of AA/aniline of 1:1. Figure 7c clearly shows that PANI nanorods with lengths of less than 1 µm had been formed



Figure 7. (a and b) AFM images of PP-g-PAA; (c) FESEM image of PP/PANI composite film 30 min after the addition of APS to the solution. The molar ratio of AA:aniline was 1:1.

and immobilized on the PP film at this time (the conversion of aniline in solution was about 10%).28b Subsequently, the PANI nanorods gradually grew into nanowires,13e,13f,26 based on the same auto-accelerated effect as discussed previously.33 When the molar ratio of AA to aniline was maintained at 1:1.2, the PANI nanoribbons could be reproducibly obtained. This was a rather remarkable result, and the growth process of the ribbons was therefore elaborately examined for with varying reaction times, as shown in Figure 8. After addition of APS during a time period of 40 min, interconnected sheetlike PANI structures were formed on the PP film surface through the grafted PAA (parts a and b of Figure 8). The thickness of these sheetlike PANI layers was about 60 nm. The petal-like nanoribbons (parts c and d of Figure 8) were observed after the polymerization had run for 120 min. It was thus believed that the sheetlike structures grew in length to eventually form the nanoribbons. The formation of the nanoribbons was completed after an additional 160 min (parts e-h of Figure 8). From parts e-h of Figure 8, particularly Figure 8g, it was apparent that the “roots” of the nanoribbons were similar to those of the sheetlike structures in parts a and b of Figure 8. However, the nanoribbons were, surprisingly, never found in the bulk solution. Several instructive hypotheses have been proposed for the formation mechanism of nanowires or fibers.5,13e,13f,26,34 Among them, a well-accepted opinion is that rigid PANIs can themselves be used as “templates” in formation of the nanostructures. This is a result of PANI having a higher reactivity than the aniline monomer. Moreover, Manohar’s group has proposed that the anilinium-peroxydisulfate ion clusters play an important role in the overall morphology of the emeraldine salt as determined from dynamic light-scattering measurements.5d

On the basis of the experimental results above as well as opinions found in the literature,5,13e,13f,26,34 we have put forward a plausible interpretation for the formation of the PANI nanoribbons. As a result of aniline being in excess (AA to aniline was 1.2), the PAA chains on the surface of the PP-g-PAA film were allowed to completely react with aniline to form a carboxylic salt. Additionally, AA-aniline may form micelles as reported with naphthalene sulfonic acid (NSA)-aniline.6c Therefore the chains of PAA-aniline salts were able to extend into the aqueous reaction solution and participate in the formation of AA-aniline micelles. After the addition of APS, the surface polymerization of aniline started from each PAAaniline chain, and subsequently, as polymerization proceeded, these PAA-PANIs could form nanorods or needles with diameters of about 70 nm. This can be likened to the aggregation of polymer brushes. After this, two processes proceeded simultaneously. One was the increase in length of the initially formed nanorods, and the other was the linking of the nanostructures in their width direction as a result of the doping or complex interaction of the PAA oligomers (assigned to AA polymerized) with the PANIs.28b From parts a and b of Figure 8, we can observe these nanorods and very loose ribbons with certain widths. The growth model implied that the PANI nanostructures would maintain a certain thickness but that their length and width would change. By careful examination of the images in Figure 8, it is not difficult to see that the widths and lengths of the nanoribbons immobilized on the PP surface increased with polymerization time whereas the thickness remained unchanged. The control of the surface wettability is of crucial importance for materials in practical applications.35 The surface wettabilty of materials is governed by both the chemical composition and


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Figure 8. SEM images displaying the growth of PANI nanoribbons at various polymerization times: (a and b) 40 min, (a) low-magnification image, (b) high-magnification image; (c and d) 120 min, (c) low-magnification image, (d) high-magnification image; (e, f, g, and h) 280 min. The AA concentration was 0.23 M, and the AA/aniline molar ratio was 1:1.2.

the roughness of a surface. The former defines whether the surface is hydrophobic or hydrophilic; whereas the latter can further magnify this hydrophobicty or hydrophilicity.36 In other words, the configuration of polymers on the surface is an

essential factor for the wettability. Many approaches have been developed to construct surface nano/microstructures to obtain a surface modification.17h,37 A previous investigation describes the fabrication of a hydrophilic surface of PP film with

Fabrication of Polyaniline Micro/Nanostructures immobilized sub-micro/nanostructured PANI dendrites.15 In the present study, the inverse scenario was observed, i.e., a hydrophobic surface was obtained with the nanostructured PANIs. The CAs of the PP films with the three PANI morphologies were measured. The average values were ∼6193, 145, and 151° corresponding to spherical particles, nanowires, and nanoribbons, respectively. When the concentration of aniline increased (also implying an increase in the molar ratio of AA/aniline from 1:0.3 to 1:0.6), the CA was found to increase from 61 to 93°. This might have been the result of the increase in hydrophobic groups in the PANI spheres. This result was similar to that reported by Ding.22 When the molar ratio of AA/ aniline was 1:1 and 1:1.2, immobilized PANI nanowires and nanoribbons were obtained on the PP film surface. These nanowires and nanoribbons gave rise to a rough surface with porous structures that covered the original PP surface (cf. Figures 3 and 4). It was considered that the hydrophobic part of the PANIs dominated the facade of the nanowires and nanoribbons. Additionally, there was much air trapped in the pores of the nanostructures. Both of these features constructed a hydrophobic shield from the environment.38 When water was dropped on the surface, it was unable to impregnate the pores and wet the modified surface. Thus the PP film grafted with nanowires and nanoribbons showed a hydrophobic or even superhydrophobic property. Conclusions In summary, shape-controllable PANIs with structures varying from spherical particles to nanowires to nanoribbons were fixated onto the surfaces of PP films. This was achieved both by tuning the conformation of PAA brushes grafted on the surfaces of the PP films and by controlling the ratio of AA to aniline. Moreover, the PAA brushes not only acted as templates for the PANI structures but also as dopants. The surfaces tethered with nanowires and nanoribbons proved to be superhydrophobic. Concisely, this innovative approach for preparing nanostructured polymers on the surface of a substrate, i.e., first introducing polymer brushes and then modulating their conformation by tuning the solution composition, has opened a new synthesis route in the development of advanced materials. It is believed that the ability to fabricate nanostructured, intrinsically conductive polymers on the surfaces of organic materials should lead to potential applications in disposable electron devices, chemical sensors and all-polymer field-effect transistors. Acknowledgment. The Major Project of the National Science Foundation of China (No. 50433040) is gratefully acknowledged for financial support. References and Notes (1) Macdiarmid, A. G. Angew. Chem., Int. Ed. 2001, 40, 2581. (2) Lu, W.; Fadeev, A. G.; Qi, B.; Smela, E.; Mattes, B. R.; Ding, J.; Spinks, G. M.; Mazurkiewicz, J.; Zhou, D.; Wallace, G. G.; Macfarlane, D. R.; Forsyth, S. A.; Forsyth, M. Science 2002, 297, 983. (3) (a) Wang, J.; Chan, S.; Carlson, R. R.; Luo, Y.; Ge, G.; Ries, R. S.; Heath, J. R.; Tseng, H-R. Nano Lett. 2004, 4, 1693. (b) Virji, S.; Huang, J.; Kaner, R. B.; Weiller, B. H. Nano Lett. 2004, 4, 491. (c) Huang, J.; Virji, S.; Weiller, B. H.; Kaner, R. B. Chem.-Eur. J. 2004, 10, 1314. (d) Ma, X.; Li, G.; Wang, M.; Cheng, Y.; Bai, R.; Chen, H. Chem.-Eur. J. 2006, 12, 3254. (4) (a) Stejshal, J.; Kratochvil, P.; Armes, S. P.; Lascelles, S. F.; Riede, A.; Helmstedt, M.; Prokes, J.; K_ivka, I. Macromolecules 1996, 29, 6814. (b) Kim, B-J.; Oh, S-G.; Han, M-G.; Im, S-S. Langmuir 2000, 16, 5841. (5) (a) Huang, J.; Kaner, R. B. Angew. Chem., Int. Ed. 2004, 43, 5817. (b) Li, D.; Kaner, R. B. J. Am. Chem. Soc. 2006, 128, 968. (c) Zhang, X.; Manohar, S. K. Chem. Commun. 2004, 20, 2360. (d) Zhang, X.; Kolla, H. S.; Wang, X.; Raja, K.; Manohar, S. K. AdV. Funct. Mater. 2006, 16, 1145. (e) Chiou, N.; Epstein, A. AdV. Mater. 2005, 17, 1679. (f) Zhong, W.; Deng,

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