10266 DOI: 10.1021/la100434b Langmuir 2010, 26(12), 10266–10270Published on Web 03/24/2010

pubs.acs.org/Langmuir

© 2010 American Chemical Society

Self-Organized Honeycomb-PatternedMicroporous Polystyrene Thin Films

Fabricated by Calix[4]arene Derivatives

Eisaku Nomura,*,† Asao Hosoda,‡ Masafumi Takagaki,‡ Hajime Mori,‡ Yasuhito Miyake,‡

Motonari Shibakami,§ and Hisaji Taniguchi‡

†Department of Material Science, Wakayama National College of Technology, 77 Noshima, Nada, Gobo,Wakayama 644-0023, Japan, ‡Industrial Technology Center of Wakayama Prefecture, 60 Ogura, Wakayama649-6261, Japan, and §Institute of Biological Resources and Functions, National Institute of Advanced Industrial

Science and Technology (AIST), Central fifth, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan

Received January 29, 2010. Revised Manuscript Received March 10, 2010

Calix[4]arene derivatives bearing carboxyl groups at the upper rim and alkyl groups at the lower rimwere synthesized.Micrometer-size porous honeycomb-patterned thin films were prepared by evaporating chloroform solution ofpolystyrene containing the calixarene derivatives under high humidity. These films were coated on gold electrodes ofQCM, and the high-frequency changes were observed to detect volatile organic compounds such as dichlorobenzene.

Inroduction

Considerable attention has been paid to patterned micropo-rous polymer thin films prepared by casting polymer solution inhigh humidity, which is known as the “breath figure” method.1-6

This technique is quite simple as follows.Micrometer-size poroushoneycomb-patterned thin films were prepared by evaporatingpolymer solution under high humidity. Micrometer-size waterdroplets as templates were condensed on the surface of the cooledpolymer solution and resulted in the highly ordered porous thinfilm after evaporation of both solvent and water. While thisphenomenon was not completely understood, the hexagonalarrangement seemed to be driven by capillary attractive forces3

and convection currents.5 Architecture of polymer was alsoan important factor to condense water microdroplets withoutcoalescence. A variety of polymers such as star polymers,1,7

rod-coil block copolymer,8 amphiphilic copoymers,2,9 bio-resource polymers,10 and other polymers11 were used for thefabricating films. Among those, the presence of hydrophilicgroups in the polymeric structure or additives seems to be animportant role to condense the water droplets and form highlyordered holes on the film surface. Various applications of thesefilms were reported as follows: tissue engineering,12 optoelectro-nics,13 superhydrophobic film,14 and so on. We considered thatthe similar honeycomb films would be fabricated by calixarenederivatives having both hydrophobic and hydrophilic groups ortheir composites. Calixarenes have been paid considerable atten-tion because of their potential utility as molecular receptors andionophores.15 We thought that the promising utilization of thecalixarene-based honeycomb-patterned films for quartz crystalmicrobalance (QCM) gas sensor would be attractive because ofan excellent molecular recognition ability of calixarenes. TheQCM technique is based on oscillation frequency shift causedby transient absorption of analytes onto quartz surface.16 Thegas sensor responses of QCM based on calixarene filmshave been studied, for example, self-assembled monolayersof calixresorcinarene derivative,17 Langmuir-Blodgett (LB)

*Corresponding author. E-mail: nomura@wakayama-nct.ac.jp.(1) Widawski, G.; Rawiso, M.; Francois, B. Nature 1994, 369, 387–389.(2) Maruyama, N.; Karthaus, O.; Ijiro, K.; Shimomura, M.; Koito, T.;

Nishimura, S.; Sawadaishi, T.; Nishi, N.; Tokura, S. Supramol. Sci. 1998, 5,331–336.(3) Pitois, O.; Franc-ois, B. Eur. Phys. J. B 1999, 8, 225–231.(4) Karthaus, O.; Maruyama, N.; Cieren, X.; Shimomura, M.; Hasegawa, H.;

Hashimoto, T. Langmuir 2000, 16, 6071–6076.(5) Srinivasarao,M.; Collings, D.; Philips, A.; Patel, S. Science 2001, 292, 79–83.(6) Stenzel, M. H. Aust. J. Chem. 2002, 55, 239–243.(7) (a) Connal, L. A.; Vestberg, R.; Gurr, P. A.; Hawker, C. J.; Qiao, G. G.

Langmuir 2008, 24, 556–562. (b) Karikari, A. S.; Williams, S. R.; Heisey, C. L.;Rawlett, A. M.; Long, T. E. Langmuir 2006, 22, 9687–9693.(8) (a) Jenkhe, S. A.; Chen, X. L. Science 1999, 283, 372–375. De Boer, B.;

Stalmach, U.; Nijland, H.; Hadziioannou, G.Adv.Mater. 2000, 12, 1581–1583. (b) Lin,C.-L.; Tung, P.-H.; Chang, F.-C. Polymer 2005, 46, 9304–9313.(9) (a) Tung, P.-H.; Huang, C.-F.; Chen, S.-C.; Hsu, C.-H.; Chang, F.-C.

Desalination 2006, 200, 55–57. (b) Tian, Y.; Liu, S.; Wang, L.; Liu, B.; Shi, Y. Polymer2007, 48, 2338–2334. (c) Bolognesi, A.; Galeotti, F.; Giovanella, U.; Bertini, F.; Yunus,S. Langmuir 2009, 25, 5333–5338.(10) (a) Nemoto, J.; Uraki, Y.; Kishimoto, T.; Sano, Y.; Funada, R.; Obata, N.;

Yabu, H.; Tanaka, M.; Shimomura, M. Bioresour. Technol. 2005, 96, 1955–1958.(b) Fukuhira, Y.; Kitazono, E.; Hayashi, T.; Kanako, H.; Tanaka, M.; Shimomura, M.;Sumi, Y. Biomaterials 2006, 27, 1797–1802. (c) Kadla, J. F.; Asfour, F. H.; Bar-Nir, B.Biomacromolecules 2007, 8, 161–165. (d) Sun, H.; Li, W.; Wu, L. Langmuir 2009, 25,10466–10472.(11) (a) Karthaus, O.; Cieren, X.; Maruyama, N.; Shimomura, M. Mater. Sci.

Eng., C 1999, 10, 103–106. (b) Yabu, H.; Tanaka, M.; Ijiro, K.; Shimomira, M.Langmuir 2003, 19, 6297–6300. (c) Xu, Y.; Zhu, B.; Xu, Y. Polymer 2005, 46, 713–717. (d) Bolognesi, A.; Mercogliano, C.; Yunus, S.; Civardi, M.; Comoretto, D.;Turturro, A. Langmuir 2005, 21, 3480–3485. (e) Deepak, V. D.; Asha, S. K. J. Phys.Chem. B 2006, 110, 21450–21459. (f) Vivek, A. V.; Babu, K.; Dhamodharan, R.Macromolecules 2009, 42, 2300–2303.

(12) (a) Nishikawa, T.; Nishida, J.; Ookura, R.; Nishimura, S.-I.; Wada, S.;Karino, T.; Shimomura,M.Mater. Sci. Eng., C 1999, 8-9, 495–500. (b) Beattie, D.;Wong, K. H.; Williams, C.; Poole-Warren, L. A.; Davis, T. P.; Barner-Kowollik, C.;Stenzel, M. H.Biomacromolecules 2006, 7, 1072–1082. (c) Tanaka, M.; Nishikawa, K.;Okubo, H.; Kamachi, H.; Kawai, T.; Matsushita, M.; Todo, S.; Shimomura, M.ColloidsSurf., A 2006, 284-285, 464–469. (d) Suuami, H.; Ito, E.; Tanaka, M.; Yamamoto, S.;Shimomura, M.Colloids Surf., A 2006, 284-285, 548–551. (e) Yamamoto, S.; Tanaka,M.; Sunami, H.; Ito, E.; Yamashita, S.; Morita, Y.; Shimomura, M. Langmuir 2007, 23,8114–8120.

(13) (a) de Boer, B.; Stalmach, U.; van Hutten, P. F.; Melzer, C.; Krasnikov,V. V.; Hadziioannou, G. Polymer 2001, 42, 9097–9109. (b) Yabu, H.; Shimomira, M.Langmuir 2005, 21, 1709–1711.

(14) Yabu, H.; Takebayashi, M.; Tanaka, M.; Shimomura, M. Langmuir 2005,21, 3235–3237.

(15) (a) Gutsche, C. D. In Calixarenes, Monographs in Supramolecular Chem-istry; Stoddart, J. F., Ed.; The Royal Society of Chemistry: Cambridge, 1989.(b) Gutsche, C. D. In Calixarenes Revisited, Monographs in SupramolecularChemistry; Stoddat, J. F., Ed.; The Royal Society of Chemistry: Cambridge, 1998.(c) Calixarenes in the Nanoworld; Vicens, J., Harrowfield, J., Eds.; Springer:Dordrecht, 2007.

(16) Nakamoto, T.; Moriizumi, T. In Artificial Olfactory System Using NeuralNetwork, Handbook of Sendors and Actuators; Yamasaki, H., Ed.; Elsevier Science:Amsterdam, 1996; Vol. 3.

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Nomura et al. Article

film of p-tert-butylcalix[6]arene,18 and nonporous castingfilms of calixarenes19,20 and calixresorcinarene derivatives.19

In their reports, the sensor responses depended on molecularstructures of calixarenes. To our best knowledge, the honey-comb-patterned films consisted of calixarene derivatives ortheir composites were not investigated. Therefore, their prop-erty of the molecular recognition is very interesting to beapplied to sensor films.

In this paper, we prepared calixarene derivatives bearingcarboxyl groups at the upper rim and alkyl groups at the lowerrim and fabricated honeycomb-patterned thin films by evaporat-ing chloroform solution containing the calixarene derivatives andpolystyrene (PS) in a given ratio under high humidity. The surfacemorphology was characterized by optical and scanning electronmicroscopy (SEM), and the molecular recognition property oftheir films was investigated by oscillation frequency shifts ofQCM coated on the gold electrodes toward various volatileorganic compounds.

Results and Discussion

The calixarenederivativeswere preparedas shown inScheme1.Alkyl groups as lipophilic groups and carboxyl groups as hydro-philic groups were introduced into the lower rim and the upperrim of the p-tert-butylcalix[4]arene (1), respectively. The calixar-ene tetraalkyl ethers 2a-cwere prepared by the reaction of 1withalkyl bromide in DMF in the presence of NaH in high yield.Formyl groups were introduced to the para positions by usinghexamethylenetetramine (HMT) and trifluoroacetic acid (Duffreaction) to give the derivatives 3a-c in moderate yields.21 Theformyl groups were oxidized to afford tetracarboxylated calixar-ene 4a-c.22 These derivatives had cone structures, in which allphenol units have same direction, determined by means of NMRspectral data which showed double doublet signals based onmethylene bridges of the calixarene ring.

The 1 mg/mL chloroform solution containing equal weightsof calixarene 4c and PS (CA%=50) was prepared and fabricatedon a glass surface by evaporating the solution under high-humidity air flow. The surface of the resulting films reflected

iridescent color, as shown in Figure 1. The optical micrographs ofthe films that were fabricated by carixarene 4c and PS in a givenratio under highhumidity are shown inFigure 2.Whateverweightratio of 4c to PS was varied from 0.1 to 0.9 in the chloroformsolution, honeycomb-patterned films having ca. 1-2 μm poreswere obtained (Figure 2a-e). However, when the chloroformsolutions of the low percentage of 4c (CA%<10) or PS-only wereused, no regulated porous films were prepared under the sameconditions (Figure 2f). We used linear standard PS havingMw =1.09� 106. In the case of linear PS bearing hydrophilic groups as aterminal group, highly regular honeycomb-microstructured mor-phology is obtained by itself.23 The SEM images of the films areshown in Figure 3. In the large area of the films, regular poreswere formed in a honeycomb structure, and the average holediameter was ca. 1-2 μm. The variation of thickness wasobserved on the film surface. In the region of thinner surfacemonolayer film having regular pores was observed as shown inFigure 3b,e,f. The film thickness of this region which wasestimated from the SEM pictures on the tilted stage at a10-30� angle was ∼1 μm in height. In the region of thickersurface, multilayer film having deep cavities that was formedaround a template of water droplets was observed as shown inFigure 3c.The thickness of this regionwas estimated at ca. 2-3μmin height. The similar honeycomb films having ca. 1-2 μm poreswere also obtained from the calixarene 4b, however, not from 4a

due to low solubility in chloroform.The calixarene-based honeycomb-patterned films were applied

for QCM-based gas sensor utilizing excellent molecular recogni-tion ability of calixarenes. The porous and nonporous films weredeposited on QCM. The gas samples used were four ethersolutions containing organic compounds as follows: A, haloga-nated compounds; B, aromatic compounds; C, halogenatedaromatic compounds; D, alcohols. A 1 μL of the mixed solutionwas injected into the glass flask which was kept at 22 �C by waterjacket after introduction of dry nitrogen gas. The mixed solutionwas gradually evaporated to fill the flask in concentrations at 100ppm in each gaseous state. Reduction of oscillation frequency ofthe film-coated QCMwas measured in 10 min after the injection.Typical results of the shifts (-ΔHz) in the fundamental oscillationfrequency are shown in Figure 4. Porous honeycomb-patternedfilm containing a composition of 10% calixarene showed largershifts than the nonporous films. Among the mixed gas (A-D)used, chlorinated aromatic hydrocarbon (C) led to relatively highchange. The frequency shifts toward each component of the

Scheme 1. Synthesis of Tetracaboxylcalixarene Derivatives

Figure 1. Opticalmicrograph of the film cast from the chloroformsolution of 4c and PS (CA%= 50). Scale bar is 1 μm long.

(18) (a) Mu~noz, S.; Nakamoto, T.; Moriizumi, T. The Transactions of TheInstitute of Electrical Engineers of Japan; 1999, 119-E, 430–435. (b) Mu~noz, S.;Nakamoto, T.; Moriizum, T. Sens. Mater. 1999, 11, 427–435.(19) (a) Koshets, I. A.; Kazantseva, Z. I.; Shirshov, Yu. M.; Cherenok, S. A.;

Kalchenko, V. I. Sens. Actuators, B 2005, 106, 177–181. (b) Dickert, F. L.; B€aumler,U. P. A.; Stathopulos, H. Anal. Chem. 1997, 69, 1000–1005.(20) Dickert, F. L.; Schuster, O. Microchim. Acta 1995, 119, 55–62.(21) Komori, T.; Shinkai, S. Chem. Lett. 1992, 901–904.(22) Sansone, F.; Barboso, S.; Casnati, A.; Fabbi, M.; Pochini, A.; Ugozzoli, F.;

Ungaro, R. Eur. J. Org. Chem. 1998, 897–905.(23) Bolognesi, A.; Mercogliano, C.; Yunus, S.; Civardi, M.; Comoretto, D.;

Turturro, A. Langmuir 2005, 21, 3480–3485.

10268 DOI: 10.1021/la100434b Langmuir 2010, 26(12), 10266–10270

Article Nomura et al.

mixed gas C were investigated under the similar conditions, andthe results are shown in Figure 5. There was no high selectivitytoward isomers of dichlorobenzene. It is obvious that porous filmincreases surface area. Higher shifts for the porous films may bebased on not only the effect of surface area but also the surfacestructure of the films. We tried to obtain information on thesurface fine structure that has honeycomb pattern by means ofFT-IR and XPS. Unfortunately, the spectral differences betweentheir nonporous and porous films for FT-IR and XPS spectrawere not observed.

The oscillation frequency shifts of the QCM coated with thecomposite films containing 0-100% of the calixarene 4c weremeasured using p-DCB gas (10 ppm). The results are shown inFigure 6. In the case of the nonporous films, the frequency

changes greatly depended on the composition of the films anddecreased with a reduction in the calixarene content. This resultshowed transient absorptionof p-DCBon the calixarenemoleculewas favored.On the other hand, the salient changes for the porousfilms were not observedwith a reduction in the calixarene contentof between 90 and 30%.The relatively large change for the porousfilm was observed in the calixarene content of 10%. It was notclear that the effect of the calixarenemolecule was not observed inthe case of porous and nonporous films with the higher concen-tration of the calixarene at CA% > 50. However, there are nosignificant difference in the honeycomb-patterned films obtainedfrom the given CA% solutions, as shown in Figures 2 and 3. Asmentioned above, no spectral differences between their nonpo-rous and porous films for the measurements of FT-IR and XPS

Figure 2. Opticalmicrographof the films formed from the chloroform solutionof 4c andPS.CA%: (a) 75, (b) 63, (c) 38, (d) 25, (e) 13, and (f)5. All scale bars are 10 μm long.

Figure 3. Scanning electronmicrographs of the films formed from the chloroform solution of 4c and PS. (a-c) CA%=50; (d-f) CA%=10. Scale bar: 10 μm long for (a, d); 1 μm long for (b, c, e, f).

DOI: 10.1021/la100434b 10269Langmuir 2010, 26(12), 10266–10270

Nomura et al. Article

spectra were detected. It was assumed that these results reflectedthe molecular arrangement of the calixarene molecule and PS onthe surface of the films. It was speculated that the calixarenemolecules were concentrated in the surface layer of the porousfilm. In the course of the fabricating process of the film, theamphiphilic calixarene molecules migrate to the interface con-tacting micrometer-size water droplets as a template, and as aresult the calixarene molecules were concentrated in the surface.This presumption could be explained by the formation of thecalixarene-based honeycomb-patterned films by stabilization of

the water droplets. By this process, the content of the calixarenecould be got the same concentration on the surface of the filmscontaining the calixarene (CA%=30-90). In the case of lowpercent of the calixarene (CA%=10), itwas assumed that suitablemolecular array of the calixarene and/or PS on the surface wasestablished at this composition.

Conclusions

Preparation and properties of the honeycomb-patterned PSfilms fabricated by the calixarene derivatives having carboxylgroups and alkyl groups were investigated. The films with regularpores were obtained in a given ratio of the calixarenes to PS. Themolecular recognition property of their films was investigated bycoating on QCM, and the large oscillation frequency shifts wereobserved toward dichlorobenzene. It was also suggested that thefine surface structure of the calixarene composite films wasestimated by means of the frequency shifts of the QCM.

Experimental Section

General. p-tert-Butylcalix[4]arene was prepared by the litera-ture method. Other solvents and reagents were purchased fromWako Pure Chemical Industries, Ltd., and used without furtherpurification. Melting points were determined by a Yanaco micromelting point apparatus and are uncorrected. 1H and 13C NMRspectra were recorded on a Varian Unity-plus 300 spectrometerand a Burker Avance-400 using a residual solvent as an internalstandard. FT-IR spectra were obtained on a Shimadzu IRPres-tige-21 FT-IR 8400S spectrometer using a single reflectionhorizontal ATR MiRacle (ZnSe). ESI-TOF MS spectra weremeasured on a positive mode using a PE Biosystems Marinerspectrometer. Scanning electron microscopy (SEM) was con-ducted on a JEOL JSM-6480LV. QCM measurements wereperformed by a Kazu Technica quartz oscillator sensor systemKZQCM1D.

Calix[4]arene Tetradodecyl Ether (2a). To a solution of0.5 g (1.18mmol) of calix[4]arene in anhydrousDMF(10mL)wasadded 0.22 g (5.6 mmol) of NaH (62% in oil). After the mixturewas stirred for 10 min at room temperature 1.41 g (5.6 mmol) ofdodecyl bromide was added. The mixture was stirred for 15 h at80 �C. Ice-water was added to the reaction mixture and stirredfor 1 h. The resulting precipitate was filtrated and washed withwater andmethanol. The precipitate was purified by recrystalliza-tion form chloroform/methanol twice and dried under reducedpressure to afford 1.12 g (86%) ofwhite crystals;mp=59-64 �C.IR (ATR): ν 2914, 2847, 1454 cm-1. 1HNMR (400MHz, CDCl3,22 �C): δ 0.90 (t, J=7.14, 12H), 1.2-1.5 (m, 72H), 1.85-2.00 (m,8H), 3.15 (d, J=13.55, 4H), 3.88 (t,J=7.42, 8H), 4.45 (d,J=13.37,4H), 6.55-6.65 (m, 12H). 13C NMR (100 MHz, CDCl3 22 �C): δ14.12, 22.71, 26.38, 29.44, 29.76, 29.83, 29.87, 29.99, 30.02 30.35,30.98, 31.97 75.14, 121.83, 128.06 135.15, 156.60. MS (ESI-TOF)m/z calcd for (MþNa)þ C76H120O4Na 1119.91; found 1119.89.

p-Tetraformylcalix[4]arene Tetradodecyl Ether (3a). Asolution of 0.4 g (0.36 mmol) of calixarene 2a and 2.0 g (14.6mmol) of hexamethylenetetramine in 15mLof trifluoloacetic acidwas refluxed for 1 day. After the reaction the mixture was pouredinto ice-water. The organic portion was extracted with ethylacetate. The organic layer was washed with water, saturatedNaHCO3, water, and brain, followed by dried overMgSO4. Afterevaporation of the solvent, the product was purified through SiO2

column (hexane/ethyl acetate = 5/1) to afford 0.23 g (53%) ofwhite crystals; mp= 112-115 �C. IR (ATR): ν 2916, 2851, 1694,1678, 1593 1462 cm-1. 1HNMR(400MHz,CDCl3, 22 �C): δ 0.86(t, J= 7.07, 12H), 1.16-1.43 (m, 72H), 1.80-1.92 (m, 8H), 3.32(d, J=13.89, 4H), 3.94 (t, J=7.45, 8H), 4.47 (d, J=13.64, 4H),7.13 (s, 8H), 9.56 (s, 4H). 13C NMR (100 MHz, CDCl3 22 �C): δ14.09, 22.68, 26.18, 29.40, 29.71, 29.77, 29.82, 29.89, 30.31, 30.90,31,92, 75.70, 130.19, 131,34, 135.58, 161.87, 191.27. MS (ESI-TOF)m/z calcd for (MþH)þC80H121O8 1209.91; found 1209.90.

Figure 4. Frequency shifts (-ΔHz) of theQCMcoat by porous ornonporous films (2 μg, CA%=10) in the presence ofmixed gases:A (CH2Cl2, CHCl3, CCl4, ClCH2CH2Cl, Cl2CdCCl2, 100 ppm), B(benzene, ethylbenzene, toluene, xylene, styrene, 100 ppm), C(chlorobenzene, o-, m-, and p-dichlorobenzene, 100 ppm), D(MeOH, cyclohexanol, 2-propanol, 1-butanol, 100 ppm).

Figure 5. Frequency shifts (-ΔHz) of the QCM coat by porousand nonporous films (2 μg, CA%=10) in the presence of 10 ppmhaloganated aromatic hydrocarbons. CB=chlorobenzene; o-DCB,m-DCB, and p-DCB=o-,m-, and p-dichlorobenzene, respectively.

Figure 6. Frequency shifts (-ΔHz) of the QCM coat by porousand nonporous films (4 μg) containing various CA% in thepresence of 10 ppm p-DCB.

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p-Tetracarboxylcalix[4]arene Tetradodecyl Ether (4a).Asolution of 0.13 g (0.107 mmol) of calixarene 3a and in 10 mL ofCHCl3 and 10mLof acetonewas cooled in an ice bath.A solutionof 132 mg (1.36 mmol) of sulfamic acid, and 102 mg (1.13 mmol)of sodium chlorite in 0.5 mL of water was added once every hourto the above solution until after the reaction was completed,checking by TLC. After the reaction the solvent was evaporatedand 10 mL of 6 M HCl was added to produce precipitate. Theprecipitate was filtrated and washed with water and methanol toafford 129mg (94%) ofwhite powder;mp>250 �C. IR (ATR): ν2916, 2851, 1697, 1686 cm-1. 1H NMR (400 MHz, THF-d8,22 �C): δ 0.89 (t, J = 7.07, 12H), 1.17-1.52 (m, 72H), 1.88-2.04 (m, 8H), 3.30 (d, J=13.64, 4H), 3.99 (t, J=7.33, 8H), 4.49(d, J = 13.39, 4H), 7.38 (s, 8H), 10.91 (bs, 4H). 13C NMR (75MHz, THF-d8 40 �C): δ 14.51, 23.67, 27.45, 30.48, 30.74, 30.81,30.90, 30.97, 31.02, 31.42, 32.02, 33.03, 76.34, 126.07, 131,36,135.70, 161.43, 168.45. MS (ESI-TOF) m/z calcd for (M þ Na)þ

C80H120O12Na 1295.87; found 1295.82.

Calix[4]arene Tetraoctyl Ether (2b). To a solution of 0.5 g(1.18 mmol) of calix[4]arene in anhydrous DMF (10 mL) wasadded 0.22 g (5.6 mmol) of NaH (62% in oil). After the mixturewas stirred for 10 min at room temperature, 1.41 g (5.6 mmol)of dodecyl bromide was added. The mixture was stirred for15 h at 80 �C. Ice-water was added to the reactionmixture andstirred for 1 h. The organic potion was extracted with chloro-form (50 mL � 2), washed with water (30 mL � 3), and driedover MgSO4. After evaporating the solvent, the product waspurified through SiO2 column (hexane/CHCl3=10/1) to afford0.76 g (74%) of white crystals; mp = 76-79 �C. IR (ATR): ν2920, 2851, 1454, 1377 cm-1. 1H NMR (400 MHz, CDCl3,22 �C): δ 0.87 (t, J =7.33, 12H), 1.2-1.4 (m, 40H), 1.80-1.95(m, 8H), 3.12 (d, J =13.14, 4H), 3.85 (t, J = 7.33, 8H), 4.42(d, J=13.14, 4H), 6.50-6.65 (m, 12H). 13C NMR (100 MHz,CDCl3 22 �C): δ 14.11, 22.72, 26.37, 29.65, 29.94, 30.37,30.98, 31.99, 75.15, 121.83, 128.06 135.16, 156.59. MS (ESI-TOF) m/z calcd for (M þ Na)þ C60H88O8Na 895.66; found895.61.

p-Tetraformylcalix[4]arene Tetraoctyl Ether (3b). Thereaction was carried out in a manner similar to that for 3a. Thisreaction afforded white crystals (39% yield); mp = 123-125 �C.IR (ATR): ν 2920, 2851, 1682, 1593 cm-1. 1H NMR (400 MHz,CDCl3, 22 �C): δ 0.87 (t, J = 7.07, 12H), 1.20-1.43 (m, 40H),1.80-1.93 (m, 8H), 3.32 (d, J=13.89, 4H), 3.94 (t, J=7.33, 8H),4.47 (d, J=13.89, 4H), 7.13 (s, 8H), 9.56 (s, 4H). 13C NMR (100MHz, CDCl3 22 �C): δ 14.07, 22.67, 26.18, 29.52, 29.77, 30.34,30.91, 31,90, 75.72, 130.20, 131,37, 135.59, 161.89, 191.30. MS(ESI-TOF) m/z calcd for (M þ H)þ C64H89O8 985.66; found985.61.

p-Tetracarboxylcalix[4]arene Tetraoctyl Ether (4b). Thereaction was carried out in a manner similar to that for 4a. Thisreaction afforded white powder (93% yield); mp>280 �C. IR(ATR): ν 2920, 2851, 1697, 1597 cm-1. 1H NMR (400 MHz,THF-d8, 22 �C): δ 0.91 (t, J=7.07, 12H), 1.26-1.51 (m, 40H),1.89-2.01 (m, 8H), 3.31 (d, J=13.39, 4H), 4.00 (t, J=7.33, 8H),4.49 (d, J=13.39, 4H), 7.38 (s, 8H), 11.08 (bs, 4H). 13CNMR(75MHz, THF-d8, 40 �C): δ 14.53, 23.69, 27.44, 30.62, 30.91, 31.42,32.01, 33.05, 76.34, 125.95, 131,40, 135.78, 161.52, 168.67. MS(ESI-TOF) m/z calcd for (M þ Na)þ C64H88O12Na 1071.62;found 1071.61.

Calix[4]arene Tetrabutyl Ether (2c). The reaction wascarried out in a manner similar to that for 2b. This reactionafforded white crystals (75% yield); mp = 118-122 �C. IR(ATR): ν 2955, 2928, 2862, 1454 cm-1. 1H NMR (300 MHz,CDCl3, 22 �C): δ 0.98 (t, J = 7.42, 12H), 1.37-1.51 (m, 8H),1.83-1.93 (m, 8H), 3.13 (d, J=13.46, 4H), 3.87 (t, J=7.35, 8H),4.43 (d, J=13.32, 4H), 6.52-6.61 (m, 12H). 13CNMR (75MHz,CDCl3 22 �C): δ 14.08, 19.36, 30.97, 32.30, 74.80, 121.84, 128.08135.14, 156.57. MS (ESI-TOF) m/z calcd for (M þ Na)þ

C44H56O4Na 671.41; found 671.38.

p-Tetraformylcalix[4]arene Tetrabutyl Ether (3c).A solu-tionof 3.0 g (4.62mmol) of calixarene2cand 23.3 g (166.32mmol)of hexamethylenetetramine in 90 mL of trifluoloacetic acid wasrefluxed for 15 h.After the reaction themixture was poured into a100 mL of ice-water. The organic portion was extracted withdichloromethane. The organic layer was washed with water,followed by dried over MgSO4. After evaporation of the solvent,the product was recrystallized from chloroform-methanol toafford 2.8 g (80%) of crystals; mp = 237-240 �C. IR (ATR): ν2959, 2932, 2866, 2789, 2720, 1686, 1694,1593 cm-1. 1H NMR(400 MHz, CDCl3, 22 �C): δ 1.01 (t, J = 7.32, 12H), 1.42-1.51(m, 8H), 1.82-1.92 (m, 8H), 3.35 (d, J=13.92, 4H), 3.98 (t, J=7.32, 8H), 4.50 (d, J= 13.92, 4H), 7.16 (s, 8H), 9.55 (s, 4H). 13CNMR (100 MHz, CDCl3 22 �C): δ 13.95, 19.21, 30.89, 32.24,75.41, 130.21, 131,37, 135.59, 161.88, 191.29. MS (ESI-TOF)m/zcalcd for (M þ Na)þ C48H56O8Na 783.39; found 783.34.

p-Tetracarboxylcalix[4]arene Tetrabutyl Ether (4c). Thereaction was carried out in a manner similar to that for 4a. Thisreaction afforded white powder (89% yield); mp > 280 �C. IR(ATR): ν2959, 2932, 2866, 2835, 1694, 1686, 1601 cm-1. 1HNMR(300MHz,DMSO-d6, 22 �C): δ 0.97 (t, J=7.31, 12H), 1.35-1.55(m, 8H), 1.80-1.88 (m, 8H), 3.39 (d, J=13.38, 4H), 3.92 (t, J=7.16, 8H), 4.35 (d, J=13.07, 4H), 7.32 (s, 8H), 12.36 (bs, 4H). 13CNMR (75 MHz, DMSO-d6, 40 �C): δ 13.51, 18.55, 29.92, 31.52,74.47, 124.50, 129.44, 134.04, 159.60, 166.47. MS (ESI-TOF) m/zcalcd for (M þ Na)þ C48H56O12Na 847.37; found 847.35.

Preparation of Honeycomb Films. The 1 mg/mL chloro-form solutions containing various weight ratios of 4 and/or PSwere prepared. PS having Mw = 1.09 � 106 (TOSOH TSKstandard PS F-128, Mw/Mn = 1.08) was used. In the case ofremaining insoluble material of 4, 1% of tetrahydrofuran may beused to dissolve it before preparation of the solution or ultrasonicirradiation may be also used. The honeycomb films were fabri-cated on a glass surface or gold electrode on QCM at roomtemperature by evaporating 2-5 μL of the solution under flow ofhigh-humidity air (relative humidity>90%, flow rate=5-10L/min). The moist air was generated by blowing air into water, andhumidity was checked by a digital hygrometer.

QCMMeasurement. The porous and nonporous films (2 or4 μg) were deposited on the gold electrode of QCM (9MHz, AT-cut, gold electrode of 4.6 mm in diameter) by a 2 or 4 μL of thechloroform solution prepared above method with using a micro-syringe. The nonporous films were prepared under flow of dry airat room temperature. Gas samples used were four ether solutionscontaining organic compounds as follows. A: haloganated com-pounds (CH2Cl2, CHCl3, CCl4, ClCH2CH2Cl, Cl2CdCCl2); B:aromatic compounds (benzene, ethylbenzene, toluene, xylene,styrene); C: halogenated aromatic compounds (chlorobenzene,o-, m-, p-dichlorobenzene); D: alcohols MeOH, cyclohexanol,2-propanol, 1-butanol). After introduction of dry nitrogen gasuntil oscillation frequency of QCMwas stable, 1 μL of the mixedsolution, which evaporated to reach the concentration at 100 ppmof each VOC in a gaseous state in a glass flask, was injected intothe flask which was kept at 22 �C by a water jacket. Reduction ofoscillation frequency of the QCM was measured in 10 min afterthe injection.

Acknowledgment. The authors gratefully acknowledge finan-cial support by the Cooperation for Innovative Technology andAdvancedResearch inEvolutional Area (CITYAREA) programfrom the Ministry of Education, Culture, Sports, Science andTechnology Japan.We thankMr. S. Niiyama andMs. H. Nakao(Industrial Technology Center of Wakayama Prefecture) for theoperation of SEM and optical microscopes. We are also gratefultoMr. K.Goto (Kazu Technica Co., Ltd.) for his assistance in aninstrumental improvement of the QCM sensor system.

Supporting Information Available: NMR spectral data forcompounds 2-4. This material is available free of charge via theInternet at http://pubs.acs.org.