Hydrogen-Bonding-Directed Layer-by-Layer Assembly of Poly(4

This paper describes the buildup of hydrogen-bonding-directed poly(4-vinylpyridine)/poly(4-vinylphenol) (PVPy/PVPh) multilayer film that was fabricate...
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Hydrogen-Bonding-Directed Layer-by-Layer Assembly of Poly(4-vinylpyridine) and Poly(4-vinylphenol): Effect of Solvent Composition on Multilayer Buildup Hongyu Zhang, Zhiqiang Wang, Yiqun Zhang, and Xi Zhang* Key Lab of Organic Optoelectronics and Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing 100084, People’s Republic of China, and Key Lab for Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130023, People’s Republic of China Received May 28, 2004. In Final Form: August 2, 2004 This paper describes the buildup of hydrogen-bonding-directed poly(4-vinylpyridine)/poly(4-vinylphenol) (PVPy/PVPh) multilayer film that was fabricated by layer-by-layer (LbL) assembly of PVPy and PVPh from an ethanol solution. UV-visible spectroscopy and Fourier transform infrared (FT-IR) spectroscopy revealed a uniform deposition process. The interaction between PVPy and PVPh was identified as hydrogen bonding through FT-IR spectroscopy and temperature-dependent IR spectral changes of the hydrogenbonded multilayer. Notably, we discussed the effect of solvent conditions on the growth of PVPy/PVPh multilayer films monitored by UV-visible spectroscopy. It was found that increasing the ratio of N,Ndimethylformamide (DMF) in the mixed ethanol/DMF solvents resulted in a marked decrease of the amount of polymers adsorbed, which was attributed to the increased polarity of the adsorption solutions. Furthermore, the solvent stability of PVPy/PVPh multilayer film in mixed ethanol/DMF solvents with different DMF ratios was also investigated. As a result, a new method for tuning the structure of hydrogen-bondingdirected multilayer film was developed.

1. Introduction Since Decher et al. introduced the method for preparing multilayer ultrathin films by the consecutive deposition of oppositely charged polyelectrolytes from dilute aqueous solution onto charged substrates, self-assembled ultrathin multilayer films through this layer-by-layer (LbL) process have been intensively investigated in recent years.1-3 The popularity of this LbL procedure is due to its simplicity, versatility, and systematical control over the structure and the thickness of the resulting films. Moreover, the materials used in LbL studies can be small organic molecules4 or inorganic compounds,5-8 macromolecules,9,10 biomacromolecules such as proteins,11,12 DNA,13 or even colloids.14,15 * Corresponding author. Current address: Key Lab of Organic Optoelectronics and Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing 100084, P. R. China. Fax: 008610-62772114. E-mail: [email protected]. (1) Decher, G.; Schlenoff, J. B. Multilayer thin filmssSequential Assembly of Nanocomposite Materials; VCH: Weinheim, Germany, 2003. (2) Decher, G.; Hong, J. D., Schmitt, J. Thin Solid Films 1992, 210/211, 831. (3) Decher, G. Science 1997, 277, 1232. (4) Zhang, X.; Gao, M. L.; Kong, X. X.; Sun, Y. P.; Shen, J. C. Chem. Commun. 1994, 1055. (5) Kleinfeld, E. R.; Ferguson, G. S. Science 1994, 265, 370. (6) Lvov, Y.; Ariga, K.; Ichinose, I.; Kunitake, T. Langmuir 1996, 12, 3038. (7) Ostrander, J. W.; Mamedov, A. A.; Kotov, N. A. J. Am. Chem. Soc. 2001, 123, 1101. (8) Liu, S. Q.; Kurth, D. G.; Bredenko¨tter, B.; Volkmer, D. J. Am. Chem. Soc. 2002, 124, 12279. (9) Laschewsky, A.; Mayer, B.; Wischerhoff, E.; Arys, X.; Joans, A. Thin Solid Films 1996, 284/285, 334. (10) He, J. A.; Valluzzi, R.; Yang, K.; Dolukhan, T.; Sun, C. M.; Kumar, J.; Tripathy, S. K.; Samuelson, L.; Balogh, L.; Tomalia, D. A. Chem. Mater. 1999, 11, 3268. (11) Kong, W.; Zhang, X.; Gao, M. L.; Zhou, H.; Li, W.; Shen, J. C. Macromol. Rapid Commun. 1994, 15, 405. (12) Lvov, Y.; Lu, Z.; Schenkman, J. B.; Zu, X.; Rusling, J. F. J. Am. Chem. Soc. 1998, 120, 4073. (13) Taton, T. A.; Mucic, R. C.; Mirkin, C. A.; Letsinger, R. L. J. Am. Chem. Soc. 2000, 122, 6305.

The driving forces for LbL assembly are primarily electrostatic and covalent bonds, but they can also involve charge transfer interaction and van der Waals interaction. Hydrogen bonding as the driving force of LbL selfassembled ultrathin films was first introduced by Rubner et al.16 and Zhang et al.17 almost simultaneously in 1997. In their work, a new concept was established for the fabrication of multilayer films by consecutively alternating the deposition of two kinds of polymers, one with hydrogenbonding-donating groups and the other with hydrogenbonding-accepting groups.16-21 Unlike electrostatically formed polyelectrolyte multilayers constructed in aqueous solutions,4-15 however, one of the advantages of the multilayers based on hydrogen bonding is that the formation of the LbL films can be also obtained in organic solvents, which opened a way for preparing multilayer structures using nonionic and water-insoluble polymers instead of water-soluble polyelectrolytes. Moreover, the relatively weak hydrogen bonds between the layered films can be readily altered, therefore providing a strategy for controlling the layered structure leading to functional multilayer materials. For example, Granick and coworkers prepared erasable hydrogen-bonded multilayers containing weak polyacids, which could be assembled at low pH and subsequently dissolved at higher pH as a consequence of increasing the ionization degree of the weak (14) Gao, M. Y.; Gao, M. L.; Zhang, X.; Yang, Y.; Yang, B.; Shen, J. C. Chem. Commun. 1994, 2777. (15) Schmitt, J.; Decher, G. Adv. Mater. 1997, 9, 61. (16) Stockton, W. B.; Rubner, M. F. Macromolecules 1997, 30, 2717. (17) Wang, L. Y.; Wang, Z. Q.; Zhang, X.; Shen, J. C.; Chi, L. F.; Fuchs, H. Macromol. Rapid Commun. 1997, 18, 509. (18) Wang, L. Y.; Fu, Y.; Wang, Z. Q.; Fan, Y. G.; Zhang, X. Langmuir 1999, 15, 1360. (19) Wang, L. Y.; Fu, Y.; Wang, Z. Q.; Wang, Y.; Sun, C. Q.; Fan, Y. G.; Zhang, X. Macromol. Chem. Phys. 1999, 200, 1523. (20) Wang, L. Y.; Cui, S, X.; Wang, Z. Q.; Zhang, X. Langmuir 2000, 16, 10490. (21) Fu, Y.; Chen, H.; Qiu, D. L.; Wang, Z. Q.; Zhang, X. Langmuir 2002, 18, 4989.

10.1021/la048685u CCC: $27.50 © 2004 American Chemical Society Published on Web 09/04/2004

H-Bonding-Directed LbL Assembly of PVPy and PVPh

polyacids.22,23 Lian et al. prepared polymer and nanoparticle composite multilayers based on hydrogen bonding.24 More noticeably, Rubner et al. developed thermal and photochemical techniques for stabilizing hydrogen-bonded multilayers and used this approach to produce micropatterned surfaces.25 Recently, Caruso et al. reported on the preparation of multilayer films comprising alternate stacks of hydrogen-bonded poly(4-vinylpyridine) (PVPy) and poly(acrylic acid) and electrostatically formed poly(sodium 4-styrenesulfonate) and poly(allylamine hydrochloride) layers via the LbL assembly technique, and their high pH sensitivity toward deconstruction.26 Sukhishvili et al. reported on the competitive role of hydrogen bonding and electrostatic interactions in the growth and stability of polyelectrolyte multilayers in a wide range of pHs.27 Very recently, on the basis of all prior work on hydrogenbonded multilayers performed in a flat geometry, hydrogen-bonded self-assembly also was used to build multilayer capsules, which could find important applications in many fields, especially in biology and medicine.28,29 There has been considerable interest recently in the investigation of the factors controlling LbL multilayer structures. Among these factors, the pH values30 and ionic strength31 of adsorption solutions were reported to be of main importance in multilayer assembly based on electrostatic interaction. Here, we attempt to develop a simple methodology for controlling the hydrogen-bonded multilayer buildup. Hence, we have employed poly(4-vinylpyridine) (PVPy) and poly(4-vinylphenol) (PVPh) as a hydrogen donor and a hydrogen acceptor, respectively, to construct hydrogen-bonding-directed multilayer films by alternating the deposition of PVPy and PVPh in a LbL fashion. In our case, the structure and properties of hydrogen-bonding-directed PVPy/PVPh multilayer films were tuned when the solvent composition of the deposition solution was changed. Furthermore, the deconstrution kinetics and desorbed amount of hydrogen-bonded multilayer can be controlled by changing the N,N-dimethylformamide (DMF) content of mixed ethanol/DMF solvents. Consequently, varying the solvent composition provides an additional means to control the film structure, which could be highly valuable for many theoretical and practical applications of LbL multilayer films. 2. Experimental Section 2.1. Materials. The polymers used in this study, poly(4vinylpyridine) (PVPy, Mw ) 60 000), poly(4-vinylphenol) (PVPh, Mw ) 20 000), and poly(ethyleneimine) (PEI, Mw ) 50 000), were obtained from Aldrich and used without further treatment. The chemical structures of PVPy and PVPh are illustrated in Figure 1. Ethanol, N,N-dimethylformamide (DMF), and other solvents used in this study were analytical grade. 2.2. Film Preparation. The LbL film was assembled on a quartz slide or a calcium fluoride (CaF2) plate. The quartz slide was used in UV-visible, X-ray reflectometry (XRR), and atomic force microscopy (AFM) measurements, and the CaF2 plate, in Fourier transform infrared (FT-IR) spectroscopy. The quartz slide and CaF2 plate need to be modified before LbL deposition. The (22) Sukhishvili, S. A.; Granick, S. J. Am. Chem. Soc. 2000, 122, 9550. (23) Sukhishvili, S. A.; Granick, S. Macromolecules 2002, 35, 301. (24) Hao, E. C.; Lian, T. Q. Chem. Mater. 2000, 12, 3392. (25) Yang, S. Y.; Rubner, M. F. J. Am. Chem. Soc. 2002, 124, 2100. (26) Cho, J.; Caruso, F. Macromolecules 2003, 36, 2845. (27) Kharlampieva, E.; Sukhishvili, S. A. Macromolecules 2003, 36, 9950. (28) Zhang, Y. J.; Guan, Y.; Yang, S. F.; Xu, J.; Han, C. C. Adv. Mater. 2003, 15, 832. (29) Kozlovskaya, V.; Ok, S.; Sousa, A.; Libera, M.; Sukhishvili, S. A. Macromolecules 2003, 36, 8590. (30) Shiratori, S. S.; Rubner, M. F. Macromolecules 2000, 33, 4213. (31) Dubas, S. T.; Schlenoff, J. B. Macromolecules 1999, 32, 8153.

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Figure 1. Water-insoluble polymers used in this study. quartz surface was modified with (4-aminobutyl)-dimethylmethoxysilane, resulting in an NH2-tailored surface, and the CaF2 surface was modified with a precursor layer of PEI. The fabrication of PVPy/PVPh ultrathin assemblies is described as follows. The NH2-terminated substrate was first immersed in a PVPy ethanol solution for 10 min. In this way, the substrate was covered with a PVPy layer, and thus, a surface tailored with hydrogen-bonding acceptors was formed. After rinsing with pure ethanol and drying under a nitrogen stream, the resulting substrate was transferred into a PVPh ethanol solution for 10 min, to add a PVPh layer. By repetition of the above two steps in a cyclic fashion, the LbL multilayer film was fabricated. The resulting multilayer films can be expressed as (PVPy/PVPh)n, where n is the number of deposition cycles (namely, the number of bilayers). 2.3. Methods. UV-visible spectra were obtained on a Shimadzu 3100 UV-visible near-IR recording spectrometer. FT-IR spectra of PVPy/PVPh multilayers were collected on a Bruker IFS 66V instrument equipped with a deuterated triglycine sulfate (DTGS) detector at a 4 cm-1 resolution. Atomic force microscopy (AFM) images were taken with a Dimension 3100 atomic force microscope under ambient conditions. The atomic force microscope was operated in the tapping mode with an optical readout using Si cantilevers. X-ray reflectometry (XRR) was carried out on a Rigaku X-ray diffractometer (D/max 2500V PC, using Cu KR radiation with a wavelength of 1.5406 Å).

3. Results and Discussion 3.1. Layer-by-Layer Buildup. UV-visible spectroscopy has proved to be a useful and facile technique for evaluating the growth process of multilayers and was thus used in the present work to monitor the LbL assembly process of PVPy/PVPh multilayer buildup. Figure 2a displays the UV-visible absorption spectra of (PVPy/ PVPh)n multilayers (with n ) 1-8) assembled on an NH2tailored quartz surface. As shown in Figure 2a, the PVPy absorption is clearly identified by the characteristic peak at 256 nm due to the π-π* transition of the pyridine ring of PVPy and the peaks at 230 and 278 nm attributed to the π-π* transition of the benzene ring of PVPh, which substantiates the incorporation of PVPy and PVPh into the multilayers. The inset of Figure 2a shows the absorbance of quartz-supported (PVPy/PVPh)n multilayer films at characteristic wavelengths (230, 256, and 278 nm) increases proportionally with the number of deposition cycles, n. This nearly linear growth of the absorption peaks indicates that an approximately equal amount of PVPy and PVPh is deposited for each adsorption procedure and that the PVPy/PVPh LbL films grow uniformly with each deposition cycle. FT-IR spectroscopy also confirms the stepwise growth of multilayer (PVPy/PVPh)n films on the PEI-coated CaF2 plate. The FT-IR spectra with n ) 0, 2, 4, 6, and 8 in the range 1650-1400 cm-1 are shown in Figure 2b. With n ) 2 PVPy/PVPh bilayers, PVPy bands at 1598, 1558, and 1418 cm-1 assigned to the ring vibration of pyridine and PVPh bands at 1512 and 1448 cm-1 ascribed to the ring vibration of benzene are more distinct. The five bands between 1650 and 1400 cm-1 were monitored during multilayer deposition in intensities linearly with the deposition number, n, further suggesting that the amount

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Figure 2. (a) UV-visible spectra of eight PVPy/PVPh bilayers, measured after each deposition cycle. The solid spectra are recorded after PVPh adsorption, and the dotted spectra, after PVPy deposition. Inset: absorbance at 230, 256, and 278 nm vs the number of deposition cycles. (b) FT-IR spectra of PVPy/ PVPh multilayer film with n ) 0, 2, 4, 6, and 8 (from bottom to top) assembled on a PEI-modified CaF2 plate. Inset: absorbance at 1598, 1558, 1512, 1448, and 1418 cm-1 vs the number of deposition cycles.

Figure 3. X-ray reflectivity curve of a six-bilayer PVPy/PVPh film deposited on a quartz substrate.

of polymers deposited during each cycle was approximately constant, which is consistent with that of the UV-visible study. X-ray reflectometry (XRR) was employed for estimating the thickness of the multilayer assembly of PVPy/PVPh, as shown in Figure 3. It is remarkable that typical Kiessig fringes, which arise from X-ray interference from the substrate-film and film-air interfaces,2 are clearly identifiable for the hydrogen-bonding-directed multilayer film (PVPy/PVPh)6. The absence of Bragg peaks in Figure 3 indicates that the gradient of the refraction index between distinct layers is not large enough to resolve such peaks, which could be attributed to the interpenetration between the neighboring layers. The presence of wellresolved Kiessig fringes proves the homogeneousness of the film. Accordingly, the thickness of the six-bilayer PVPy/

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Figure 4. FT-IR spectra recorded at room temperature for pure PVPy (curve a), pure PVPh (curve b), and multilayer (PVPy/ PVPh)6 film (curve c) in (A) the hydroxyl region and (B) the pyridine region.

PVPh film was calculated to be 20.5 nm, and the thickness of the layer pair was thus estimated to be 3.4 nm. 3.2. Driving Force for PVPy/PVPh Multilayer Fabrication. The driving force for the construction of the PVPy/PVPh multilayer films was identified by FT-IR spectroscopy. Figure 4 shows the FT-IR spectra of PVPh, PVPy, and the eight-bilayer PVPy/PVPh film recorded at room temperature. Hydrogen-bonding formation between pyridine and phenolic hydroxyl groups leads to characteristic splitting patterns in the IR absorption of the hydroxyl and the pyridine, respectively. In the hydroxyl region of PVPh (Figure 4A, curve b), the hydroxyl band of pure PVPh consists of two components: a broad band centered at 3375 cm-1, attributed to the hydrogen-bonded hydroxyl groups (self-association), and a relatively narrower band at 3525 cm-1, assigned to the free (nonassociated) hydroxyl groups. In PVPy/PVPh multilayer film, the appearance of an absorption band at 3124 cm-1 (Figure 4A, curve c) indicates that the intermolecular hydrogen bonding is formed between PVPh and PVPy. However, the intensity of the free hydroxyl band and self-associated hydroxyl band of the film is not reduced drastically, suggesting that there is a considerable number of hydroxyl groups that is not involved in intermolecular association during the multilayer buildup. Besides the hydroxyl stretching region, some characteristic modes of the pyridine ring are also sensitive to hydrogen-bonding association. Unfortunately, due to the complication of overlapping with other structure modes of the component polymer chain, only the band at 993 cm-1 can be used to identify the existence of hydrogenbonding interactions between the pyridine groups and the phenolic groups. Figure 4B, curve c, shows the FT-IR spectra in the 1030-970 cm-1 region of PVPy/PVPh multilayer film. Pure PVPy (see curve a) has a band at 993 cm-1 ascribed to pyridine ring absorption, and pure PVPh has a band at 1014 cm-1. The two bands are well-

H-Bonding-Directed LbL Assembly of PVPy and PVPh

Figure 5. FT-IR spectra of PVPy/PVPh multilayer film as a function of temperature.

separated, and no overlap is observed. In PVPy/PVPh multilayer film, a new band around 1006 cm-1 is manifested, which provides further evidence that the multilayer is assembled via hydrogen bonding. To gain more information about the changes of hydrogen bonding between the neighboring layers within the PVPy/ PVPh multilayer film, in situ temperature-dependent FTIR measurements were carried out. FT-IR spectra in the pyridine region, shown in Figure 5, illustrate the effect of heating on a PVPy/PVPh multilayer. As previously discussed, there are two peaks at 1006 and 993 cm-1 in Figure 4B, curve c, which are assigned to the characteristic hydrogen-bonding and free pyridine bands. In Figure 5, we can find that, with an increase in temperature from 25 to 150 °C, there is a gradual decrease in intensity of the band around 1006 cm-1 and, simultaneously, an increase in intensity of the band around 993 cm-1. This result indicates that the hydrogen bonding between PVPy and PVPh alternating layers can be weakened upon increasing temperature. When heating the multilayer at 150 °C for 30 min and then cooling to room temperature, AFM observation shows that there is no obvious change in the surface morphology before and after heating treatment. 3.3. Structure Control by Organic Solvent. The effect of the solvent composition on the PVPy/PVPh multilayer buildup was examined by preparing multilayer films from ethanol/DMF mixtures. Because PVPy and PVPh both absorb in the UV region, UV-visible spectroscopy is a feasible and reliable tool for investigating the influence of the solvent on the film growth. In this case, it was found that, at various DMF fractions in ethanol/DMF solvents (containing up to 50 vol %), a linear growth could be observed at 230, 256, and 278 nm, respectively. Figure 6 shows the plot of the absorbance of polymers at 230 nm versus the number of bilayers deposited onto NH2-modified quartz substrates for deposition solutions at various DMF fractions in ethanol/DMF solvents. From Figure 6, it can be seen that a linear relationship was observed at all DMF contents, indicating that, for the selected PVPy/PVPh system, the LbL selfassembly method allows a high level of control over the hydrogen-bonded multilayer deposition process. Furthermore, we can find that the adsorbed amounts of PVPy and PVPh are both decreased when increasing the content of DMF in the ethanol/DMF solvents, which indicates that hydrogen-bonded multilayer structures can be tuned by varying the solvent composition of dipping solutions. When the volume ratio of DMF is above 45 vol %, the multilayer cannot be obtained from the mixed solvents. Hence, there exists a critical DMF content above which no multilayer growth is possible. Recently, Schlenoff et al.31 and Caruso

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Figure 6. Absorbance at 230 nm vs the number of deposition cycles from the ethanol/DMF mixtures (DMF content: 0, 10, 30, 40, 45, and 50 vol %).

Figure 7. AFM height images of a three-bilayer PVPy/PVPh film fabricated from ethanol/DMF mixtures with the following different DMF contents: (a) 0, (b) 30, (c) 40, and (d) 45 vol %.

et al.32 reported that solvent quality could have an influence on the growth of polyelectrolyte multilayer films from water/ethanol mixtures. For their selected systems, they found a considerable increase in the overall thickness of polyelectrolyte multilayers with increasing ethanol content in the adsorption solvents. In our experiments, however, increasing the DMF content in ethanol/DMF solvents results in increasing the polarity of the adsorption solutions. PVPy/PVPh multilayer films tend to desorb more in organic solvents with higher polarities. Among the factors controlling the structure of multilayers, the ionic strength and pH value of the adsorption solutions and the charge density and molecular weight of the building polymers are reported to be of main importance. According to our previous discussion, it is clear that organic solvent composition offers another alternative in controlling hydrogen-bonding-directed multilayer structure. The influence of solvent composition on the surface morphology of the PVPy/PVPh multilayers was investigated by AFM. As shown in Figure 7a, the AFM image demonstrates a good coverage of the PVPy/PVPh film when fabricating the film in pure ethanol. The roughness of the film image was analyzed with nanoscope III software. The mean roughness (Ra) is calculated to be ∼1.9 nm within a given area of 2 × 2 µm2. When fabricating the film in a solvent mixture of ethanol and DMF, the surface (32) Poptoshev, E.; Schoeler, B.; Caruso, F. Langmuir 2004, 20, 829.

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greatly. The inset in Figure 8 shows that, in the case of six-bilayer PVPy/PVPh films deposited onto an NH2modified quartz substrate, the typical absorbance peaks of PVPy and PVPh at 230, 256, and 278 nm monotonically decreased from 0 to 100 vol % DMF content in mixed ethanol/DMF solvents. The above analysis indicates that, when the LbL film is dipped into mixed ethanol/DMF solvents with high DMF contents, the multilayer can be desorbed from the film and its deconstruction ratio can be controlled by adjusting the DMF content of the mixed solvents. 4. Conclusions Figure 8. Deconstruction kinetics of a six-bilayer PVPy/PVPh mutilayer film immersed in ethanol/DMF mixtures with different DMF contents for 5 min. Inset: UV-visible absorption spectra of separated (PVPy/PVPh)6 films after immersion in mixed solvents.

roughness can decrease a little bit depending on the content of DMF, as shown in Figure 7b and c. However, there is no film formed on the substrate anymore, when the DMF content is above 45%, see Figure 7d, which agrees well with the UV absorption data. Sukhishvili and Granick22,23 demonstrated that hydrogen-bonded multilayer films dissolve upon changes in environmental pH, and Caruso et al.33 constructed the thermoreponsive ultrathin films of poly(N-isopropylacrylamide) based on hydrogen bonding, which is sensitive to environmental temperature. Herein, we measured the change of film absorbance as a function of DMF content for multilayers exposed to solvents of varying DMF contents. Figure 8 illustrates the controlled deconstruction exposed to varying DMF contents for 5 min by changes of the environmental conditions. It indicates that, in the mixed ethanol/DMF solvents, PVPy/PVPh multilayer films are not stable and are prone to destruction, and the deconstruction process of the multilayer films depends sensitively on the DMF content of the ethanol/DMF solvents. From Figure 8, it can be seen that, with an increase in the DMF content of the mixed solutions from 0 to 40 vol %, the loss rate of the multilayer film increases (33) Quinn, J. F.; Caruso, F. Langmuir 2004, 20, 20.

In this article, we presented the fabrication and detailed characterization of the poly(4-vinylpyridine)/poly(4-vinylphenol) (PVPy/PVPh) LbL film based on hydrogen bonding. The assembling process, structure, surface morphology, and interaction between the two polymers of the LbL films were carefully characterized by UV-visible spectroscopy, FT-IR spectroscopy, AFM, and XRR. A general methodology of employing mixed solvents as deposition solutions to control the film growth was established. In our case, the polarity of the deposition solutions was varied by the addition of DMF to the dipping solution. Increasing the DMF content in the adsorption solution resulted in a marked decrease of the adsorbed amount of polymers onto solid substrates. Hence, a structure-controlled multilayer film was available by increasing or decreasing the polarity of the dipping solution. The deconstruction ratio of the hydrogen-bonded multilayer could be controlled by adjusting the DMF content of the mixed solvents. In summary, organic solvent can influence the structure of hydrogen-bonding-directed multilayer film, which offers a new and general approach for constructing thin films with a controlled and tailored structure. Acknowledgment. This research is supported by the Major State Basic Research Development Program (G2000078102), National Natural Science Foundation of China (20334010), and “863” project (2003AA302140), P. R. China. LA048685U