Aggregation Behavior of Amphiphilic Phthalocyanine Block

Andrés de la Escosura , M. Victoria Martínez-Díaz , Tomás Torres , Robert H. Grubbs , Dirk M. Guldi , Helmut Neugebauer , Christoph Winder , Marti...
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Langmuir 2002, 18, 7683-7687

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Aggregation Behavior of Amphiphilic Phthalocyanine Block Copolymers Mutsumi Kimura,*,†,‡ Hiroyuki Ueki,‡ Kazuchika Ohta,‡ Kenji Hanabusa,‡ Hirofusa Shirai,*,‡ and Nagao Kobayashi§ Presto, Japan Science and Technology Corporation (JST), and Department of Functional Polymer Science, Faculty of Textile Science and Technology, Shinshu University, Ueda 386-8567, Japan, and Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8587, Japan Received March 20, 2002. In Final Form: June 12, 2002 Novel amphiphilic poly(norbornene)s were prepared from two different monomers bearing a copper phthalocyanine and a branched hydrophilic side chain through a ring-opening metathesis reaction using a ruthenium initiator. The phthalocyanine moieties were contained as a side chain of the resulting poly(norbornene) backbone. The aggregation behavior of the amphiphilic phthalocyanine diblock copolymer was investigated by a monolayer experiment at a water-air interface, transmission electron microscopy (TEM), and atomic force microscopy (AFM). The copolymer formed organized films at a water-air interface by using pure water as the subphase. Furthermore, 8 in an alkaline aqueous solution formed spherical micelles observed by TEM and AFM.

Introduction The precise construction of functional molecular materials, which are formed by the self-organization of designed functional molecular building blocks, is a subject of great importance because it controls the macroscopic properties of nanoscopic molecular devices.1 Many strategies have been explored to control the organization of molecular building blocks into unique large-scale organized states such as fibers, wires, channels, giant micelles, two-dimensional sheets, and cages.2 Since the elucidation of the structure of the light-harvesting antenna LH2 in a natural purple photosynthetic bacterium,3 the assemblies of porphyrin and phthalocyanine have attracted intense attention. The control of spatial arrangement and orientation of these planar π-conjugated compounds promised the creation or modification of functions and properties of molecular organizations. A number of porphyrins and phthalocyanines have been designed for the construction of supramolecular structures through self-organizing processes using noncovalent intermolecular interactions.4-6 Nolte et al. reported the spontaneous formation of a micrometer-sized ring-shaped architecture containing an ordered arrangement of hexakis porphyrinato benzenes that mimics the cyclic arrangement of bacteriochlorophyll chromophores.7 We report here on syntheses of novel amphiphilic diblock copolymers containing phthalocyanine aggregates by ring†

Presto, Japan Science and Technology Corp. Shinshu University. § Tohoku University. ‡

(1) Supramolecular Materials and Technologies; Reinhoudt, D. N., Ed.; Perspectives in Supramolecular Chemistry, Vol. 4; John Wiley & Sons: New York, 1999 and references therein. (2) (a) Reichert, A.; Ringsdorf, H.; Schuhmacher, P. Comprehensive Supramolecular Chemistry; Atwood, J. L., Davies, J. E. D., Macnicol, D. D., Vo¨gtle, F., Lehn, J.-M., Sauvage, J.-P., Hosseini, M. W., Eds.; Pergamon: New York, 1996; Vol. 9, p 313. (b) Kunitake, T. Comprehensive Supramolecular Chemistry; Atwood, J. L., Davies, J. E. D., Macnicol. D. D., Vo¨gtle, F., Lehn, J.-M., Sauvage, J.-P., Hosseini, M. W., Eds.; Pergamon: New York, 1996; Vol. 9, p 351. (c) Fuhrhop, J.-H. Comprehensive Supramolecular Chemistry; Atwood, J. L., Davies, J. E. D., Macnicol, D. D., Vo¨gtle, F., Lehn, J.-M., Sauvage, J.-P., Hosseini, M. W., Eds.; Pergamon: New York, 1996; Vol. 9, p 407. (3) McDermott, G.; Prince, S. M.; Freer, A. A.; HawthornthwaiteLawless, A. M.; Papiz, M. Z.; Cogdell, R. J.; Isaacs, N. W. Nature 1995, 374, 517.

opening metathesis polymerization (ROMP). Metathesis reactions of olefins catalyzed by the ruthenium catalyst (PCy3)2Cl2Ru(dCHC6H5) have been utilized in the construction of polymeric materials with controlled molecular structures and sizes.8 This highly effective ruthenium catalyst has been shown to polymerize strained cyclic olefins such as cyclobutenes and norbornenes bearing a large variety of side groups without heating and radical generation.9 The ROMP of two functionalized norbornenes yielded well-defined block copolymers including two (4) (a) Ruhlmann, L.; Schulz, A.; Giraudeau, A.; Messerschmidt, C.; Fuhrhop, J.-H. J. Am. Chem. Soc. 1999, 121, 6664. (b) Donner, D.; Bo¨ttcher, C.; Messerschmidt, C.; Siggel, U.; Fuhrhop, J.-H. Langmuir 1999, 15, 5029. (c) Tomioka, N.; Takasu, D.; Takahasahi, T.; Aida, T. Angew. Chem., Int. Ed. 1998, 37, 1531. (d) Choi, M.-S.; Aida, T.; Yamazaki, T.; Yamazaki, I. Angew. Chem., Int. Ed. 2001, 40, 3194. (e) Nakano, A.; Yamazaki, T.; Nishimura, Y.; Yamazaki, I.; Osuka, A. Chem.sEur. J. 2000, 6, 3254. (f) Aratani, N.; Osuka, A.; Kim, Y. H.; Jeong, D. H.; Kim, D. Angew. Chem., Int. Ed. 2000, 39, 1458. (g) Ogawa, K.; Zhang, T.; Yoshikawa, K.; Kobuke, Y. J. Am. Chem. Soc. 2002, 124, 22. (h) Yu, L.; Lindsey, J. S. J. Org. Chem. 2001, 66, 7402. (i) Kuroda, Y.; Sugou, K.; Sasaki, K. J. Am. Chem. Soc. 2000, 122, 7833. (j) Michelsen, U.; Hunter, C. A. Angew. Chem., Int. Ed. 2000, 39, 764. (5) (a) Toupance, T.; Ahsen, V.; Simon, J. J. Am. Chem. Soc. 1994, 116, 5352. (b) vam Nostrum, C. F.; Bosman, A. W.; Gelinck, G. H.; Schouten, P. G.; Warman, J. M.; Kentgens, A. P. M.; Devillers, M. A. C.; Meijerink, A.; Picken, S. J.; Sohling, U.; Schouten, A.-J.; Nolte, R. J. M. Chem.sEur. J. 1995, 1, 171. (c) Fox, J. M.; Katz, T. J.; Elshocht, S. V.; Verbiest, T.; Kauranen, M.; Persoons, A.; Thongpanchang, T.; Krauss, T.; Brus, L. J. Am. Chem. Soc. 1999, 121, 3453. (d) Engelkamp, H.; Middelbeek, S.; Nolte, R. J. M. Science 1999, 284, 785. (e) Kingsbough, R. P.; Swager, T. M. Angew. Chem., Int. Ed. 2000, 39, 2897. (f) Cook, M. J.; Heeney, M. J. Chem.sEur. J. 2000, 6, 3958. (g) Drager, A. S.; Zangmeister, R. A. P.; Armstrong, N. R.; O’Brien, D. F. J. Am. Chem. Soc. 2001, 123, 3595. (6) (a) Kimura, M.; Muto, T.; Takimoto, H.; Wada, K.; Ohta, K.; Hanabusa, K.; Shirai, H.; Kobayashi, N. Langmuir 2000, 16, 2078. (b) Kimura, M.; Wada, K.; Ohta, K.; Hanabusa, K.; Shirai, H.; Kobayashi, N. J. Am. Chem. Soc. 2001, 123, 2438. (7) Biemans, H. A. M.; Rowan, A. E.; Verhoeven, A.; Vanoppen, P.; Latterini, L.; Foekema, J.; Schenning, A. P. H. J.; Meijer, E. W.; de Schryver, F. C.; Nolte, R. J. M. J. Am. Chem. Soc. 1998, 120, 11054. (8) (a) Clark, T. D.; Ghadiri, R. J. Am. Chem. Soc. 1995, 117, 12364. (b) Wech, M.; Mohr, B.; Maughon, B. R.; Grubbs, R. H. Macromolecules 1997, 30, 6430. (c) Wech, M.; Jackiw, J. J.; Rossi, R. R.; Weiss, P. S.; Grubbs, R. H. J. Am. Chem. Soc. 1999, 121, 4088. (d) Wendland, M.; Zimmerman, S. C. J. Am. Chem. Soc. 1999, 121, 1389. (e) Schultz, L. G.; Zhao, Y.; Zimmerman, S. C. Angew. Chem., Int. Ed. 2001, 40, 1962. (f) Kidd, T. J.; Leigh, D. A.; Wilson, A. J. J. Am. Chem. Soc. 1999, 121, 1599. (g) Wech, M.; Mohr, B.; Sauvage, J.-P.; Grubbs, R. H. J. Org. Chem. 1999, 64, 5463. (h) Reichwein, J. F.; Wels, B.; Kruijtzer, J. A. W.; Versluis, C.; Liskamp, R. M. J. Angew. Chem., Int. Ed. 1999, 38, 3684.

10.1021/la020275n CCC: $22.00 © 2002 American Chemical Society Published on Web 08/20/2002

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Langmuir, Vol. 18, No. 20, 2002 Scheme 1

different chemical components with low polydispersities. In this context, we designed two norbornene-based monomers 1 and 2 to yield amphiphilic phthalocyanine block copolymers (Scheme 1). Phthalocyanines and their metal complexes have been incorporated within macromolecular structures as a side group, in the main chain, and in a polymeric network,10 but block copolymers including phthalocyanines are rare. Moreover, block copolymers spontaneously self-organize to produce various nanoscopic objects such as spherical, rodlike, and univesicular or lamellar structures.11 Self-organization of amphiphilic block copolymers may lead to the formation of new nanoscopic objects containing highly concentrated phthalocyanine aggregates. Results and Discussion Synthesis of Monomers. Scheme 1 shows the synthesis of two norbornene monomers 1 and 2. A phthalonitrile 3 bearing a norbornene unit was prepared from the aromatic nucleophilic substitution reaction between 5-norbornene-2-methanol (mixture of endo and exo) and 4-nitrophthalonitrile in a 60% yield.12 Refluxing 4-tertbutylphthalonitrile and 3 in a 3:1 molecular ratio in 2-(dimethylamino)ethanol (DME) with CuCl2 provided the unsymmetrical copper phthalocyanine 1 possessing one peripheral norbornene.13 The purity of 1 was checked by matrix-assisted laser desorption ionization time-of-flight mass spectroscopy (MALDI-TOF-Ms), elemental analysis, (9) (a) Nguyen, S. T.; Johnson, L. K.; Grubbs, R. H.; Ziller, J. W. J. Am. Chem. Soc. 1992, 114, 3974. (b) Dias, E. L.; Nguyen, S. T.; Grubbs, R. H. J. Am. Chem. Soc. 1997, 119, 3887. (10) McKeown, N. B. J. Mater. Chem. 2000, 10, 1979 and references therein. (11) (a) Tew, G. N.; Pralle, M. U.; Stupp, S. I. Angew. Chem., Int. Ed. 2000, 39, 517. (b) Stalmach, U.; de Boer, B.; Post, A. D.; van Hutten, P. F.; Hadziioannou, G. Angew. Chem., Int. Ed. 2001, 40, 428. (c) Harada, A.; Kataoka, K. Science 1999, 283, 65. (12) Snow, A. W.; Jarvis, N. L. J. Am. Chem. Soc. 1984, 106, 4706. (13) (a) Gouloumis, A.; Liu, S.-G.; Sastre, AÄ .; Va´zquez, P.; Echegoyen, L.; Torres, T. Chem.sEur. J. 2000, 6, 3600. (b) Kimura, M.; Wada, K.; Ohta, K.; Hanabusa, K.; Shirai, H.; Kobayashi, N. Macromolecules 2001, 34, 4706.

Kimura et al. Scheme 2

and high-performance liquid chromatography (HPLC).14 The MALDI-TOF-Ms spectrum of 1 exhibits only an expected parent molecular ion peak at 866 g/mol. The other norbornene monomer 2 was synthesized by coupling of norborn-2-ene-5-carbonyl chloride with Behera’s amine.15 The tert-butyl group can be cleaved almost quantitatively with formic acid to generate a hydrophilic carboxylic acid. The coupling reaction in the presence of triethylamine gave 2. The monomer 2 containing three tert-butyl esters was fully characterized by 1H NMR, 13C NMR, Fourier transform infrared (FT-IR) spectroscopy, and elemental analysis. Synthesis of Poly(norbornene)s. Before synthesizing block copolymers from 1 and 2, polymers with one pendant group were studied. Polymerizations of the norbornene monomers 1 and 2 with the initiator (PCy3)2Cl2Ru(d CHC6H5) were accomplished according to the literature method reported by Grubbs et al.16 The monomers were polymerized for 12 h at 45 °C in degassed toluene. Polymerizations were quenched by treatment with an excess of isobutyl vinyl ether to cleave the catalyst from the end of the polymer chain. Purification of the reaction mixture by gel permeation chromatography (GPC) (BioBeads SX-1, 200-400 mesh, eluting with tetrahydrofuran (THF)) to remove the catalyst resulted in poly(norbornene)s 4 and 5 as glassy solids (Scheme 2). The numberaveraged molecular weights (Mn) and the molecular weight distributions (PDI) are collected in Table 1. Polymers 4 and 5 displayed only glass transition temperatures at 5.7 and 14.1 °C, respectively. The absorption spectrum of monomer 1 features a strong, sharp peak at 678 nm, which is attributed to the Q-band of the copper phthalocyanine moiety.17 The sharp peak suggests that the copper phthalocyanine moiety is (14) NMR analyses of 1, 4, 6, and 8 are impossible because of the paramagnetic nature of copper phthalocyanines. (15) Newkome, G. R.; Behara, R. K.; Moorefield, C. N.; Baker, G. R. J. Org. Chem. 1991, 26, 7126. (16) (a) Maughon, B. R.; Weck, M.; Mohr, B.; Grubbs, R. H. Macromolecules 1997, 30, 257. (b) Maynard, H. D.; Okada, S. Y.; Grubbs, R. H. Macromolecules 2000, 33, 6239. (17) Stillman, M. J.; Nyokong, T. Phthalocyanines: Properties and Applications; Leznoff, C. C., Lever, A. B. P., Eds.; VCH: New York, 1989; Vol. 1, pp 135-247.

Amphiphilic Phthalocyanine Block Copolymers

Langmuir, Vol. 18, No. 20, 2002 7685 Scheme 3

Table 1. Polymerization Results for Norbornene Monomers 1-3 monomer

polymer

[M]/[I]

Mna

PDIa

Tgb (°C)

1 2 2+1 2+3

4 5 6 7

5 10 5/10/1c 5/10/1d

6300 3600 9200 10200

2.20 1.80 1.90 1.86

5.6 14.0 7.2 6.8

a Determined by gel permeation chromotography in THF relative to monodisperse polystyrene standards. b Analysis by differential scanning calorimetry with a scan rate of 10 °C/min. c [2]/[1]/[I]. d [2]/[3]/[I].

in a monomeric condition. In contrast, poly(norbornene) 4 containing copper phthalocyanines as a pendant group exhibited a broad absorption band around 620 nm. This shift is caused by exciton coupling between neighboring phthalocyanine moieties in an aggregate within the polymer chain.17 While the Q-band of the concentrated monomer solution ([1] ) 1.1 × 10-4 mol L-1) was broadened and blue-shifted due to intermolecular aggregation, the spectral shapes of 4 remained unaltered at varying polymer concentrations ([4] ) 0.0052-0.2 mg/mL). The GPC analysis of 4 revealed Mn ) 6300 with PDI ) 2.20 (relative to monodisperse polystyrene standards). To evaluate the exact mass of the polymer, MALDI-TOF-Ms spectroscopy was applied to poly(norbornene) 4. The spectrum of 4 shows a dominant set of peaks corresponding to m/z of 3595 (tetramer), 4461 (pentamer), 5333 (hexamer), 6204 (heptamer), 7070 (octamer), 7939 (nonamer), 8805 (10-mer), 9670 (11-mer), 10542 (12-mer), 11407 (13mer), 12279 (14-mer), 13144 (15-mer), and 14014 (16-mer). The disklike phthalocyanine compounds can form columnar aggregates containing a face-to-face stacking of numerous disks through their strong π-π interaction.18 However, the cast film of 4 did not show any sharp (18) (a) Simon, J.; Toupance, T. Comprehensive Supramolecular Chemistry; Atwood, J. L., Davies, J. E. D., MacNicol, D. D., Vo¨gtle, F., Eds.; Pergamon: New York, 1996; Vol. 10, p 637. (b) van Nostrum, C. F.; Nolte, R. J. M. Chem. Commun. 1996, 2385.

reflection peaks at the range of 2θ ) 2-40° for a powder X-ray diffraction (XRD) measurement, suggesting that the polymer 4 is almost amorphous. Synthesis of Diblock Copolymers. The synthesis of a diblock copolymer 6 was accomplished by sequential polymerization of 2 followed by 1 using (PCy3)2Cl2Ru(d CHC6H5) (Scheme 3).16 After complete ROMP polymerization of 2 as determined by 1H NMR and GPC, the second monomer 1 was injected and polymerization was continued for 24 h. After the evaporation of solvent, the residue was separated two fractions by gel permeation chromatography. The front-running fraction contained a high-molecular-weight product with Mn ) 9200 g/mol analyzed by GPC. Precipitation in methanol produced the diblock copolymer 6 as a blue glassy solid in a 60% isolated yield. To determine the molecular composition of the diblock copolymer, we synthesized diblock copolymer 7 from 3 and 2 by using the same procedure as for the preparation of 6.14 1H NMR spectra of 7 indicated that the molecular composition of 7 corresponded to the molar ratio in the feed of each monomer. The diblock copolymer 7 was composed of a 1:2 mixture of phthalonitrile and ester pendant groups. The amphiphilic block copolymer 8 was synthesized by the treatment of 6 with formic acid.15 In the FT-IR spectra of 6, the absorption band is present at 1730 cm-1 (CdO) due to the tert-butyl ester groups. After removal of the tert-butyl groups by formic acid, the absorption band corresponding to carboxylic acids at 1716 cm-1 is observed. The diblock copolymer 6 was not soluble in an aqueous solution. On the other hand, the hydrolyzed diblock copolymer 8 dissolved in an alkaline aqueous solution (pH > 10.0). The absorption spectra of both copolymers 6 and 8 exhibited a broad Q-band similar to that of the homopolymer 4, indicating that the copper phthalocyanine moieties within 6 and 8 were aggregated. Aggregation Behavior of Amphiphilic Diblock Copolymer. The aggregation behavior of amphiphilic diblock copolymer 8 was studied by monolayer experi-

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Langmuir, Vol. 18, No. 20, 2002

Figure 1. Surface pressure vs area per molecule isotherms for 8 on triply distilled water at 25 °C.

ments at the water-air interface, transmission electron microscopy (TEM), and atomic force microscopy (AFM) measurements. A number of reports have appeared on the aggregation behavior of low-molecular-weight phthalocyanines at a water-air interface using the LangmuirBlodgett (LB) technique.19 However, the reports on the aggregation behavior of polymeric phthalocyanines are very few. Wegner et al. elucidated the morphological dependence on pressure of phthalocyaninato-polysiloxane monolayers at the water-air interface.20 Nolte et al. reported the circular dichroism spectrum of an LB film made of an optically active phthalocyaninato-polysiloxane.21 Since the amphiphilic property of 8 is thought to be favorable for the construction of well-organized films, we investigated the aggregation behavior of 8 on a waterair interface. The orientation of the molecules can be obtained from the surface pressure versus area (π-A) isotherm, and the limiting molecular area in the solid state provides information regarding the orientation of the molecules with respect to the subphase. Figure 1 shows the π-A isotherm of 8 on pure water as the subphase. Surface pressure begins to rise at a molecular area of ca. 10 nm2, and the pressure is slowly increased up to 25 mN/m on further compression. The limiting molecular area per molecule of 8 is estimated as ca. 8 nm2 determined by extrapolating the slope of the π-A isotherm in the liquid-condensed region to zero pressure. This value is nearly twice the molecular dimension of the phthalocyanine plane (3.9 nm2) which was estimated by the CoreyPauling-Koltun (CPK) molecular model, as shown in the inset of Figure 3. The amphiphilic character of 8 favors the alignment of the phthalocyanine planes parallel to the water surface. Above pH 10.0, 8 dissolved in aqueous solution due to ionization of carboxylic acids. The morphologies of the aggregate in the aqueous solution were examined by TEM and AFM studies. Samples were prepared by drop-casting films of 8 from the 0.01 M NaOH aqueous solution onto a carbon-coated grid. The amphiphilic diblock copolymer 8 produced a good contrast in TEM without staining, and spherical objects were observed with a diameter of (19) (a) Kobayashi, N.; Lam, H.; Nevin, W. A.; Janda, P.; Leznoff, C. C.; Koyama, T.; Monden, A.; Shirai, H. J. Am. Chem. Soc. 1994, 116, 879 and references therein. (b) van Nostrum, C. F.; Picken, S. J.; Schouten, A.-J.; Nolte, R. J. M. J. Am. Chem. Soc. 1995, 117, 9957. (c) Smolenyak, P.; Peterson, R.; Nebesny, K.; To¨rker, M.; O’Brien, D. F.; Armstrong, N. R. J. Am. Chem. Soc. 1999, 121, 8628. (20) Yase, K.; Schwiegk, S.; Lieser, G.; Wegner, G. Thin Solid Films 1992, 213, 130. (21) Engelkamp, H.; van Nostrum, C. F.; Picken, S. J.; Nolte, R. J. M. Chem. Commun. 1998, 979.

Kimura et al.

Figure 2. (a) Transmission electron micrograph of spherical organizations made of 8. (b) Atomic force microscopic image of an assembly of 8 on mica. As the coordinate out of the plane of the page increases to its maximum, 7.8 nm, the shade becomes lighter.

Figure 3. Schematic illustration of the spherical organization of 8 in an alkaline aqueous solution.

approximately 8 nm (Figure 2a). The dark image is ascribed to highly concentrated phthalocyanine moieties. The spin-coated film of 8 onto a mica substrate was studied by AFM in the tapping mode (Figure 2b). The AFM images also show many particles. The diameters of 25 particles were found to be between 11.2 and 22.4 nm, and the average was 14.0 nm. From these results, we may conclude that the amphiphilic diblock copolymer 8 self-organized in aqueous media to produce micellar aggregates by segregation between a hydrophobic polymeric phthalocyanine segment and a hydrophilic ionized segment, as shown in Figure 3. Conclusion We synthesized poly(norbornene)s containing copper phthalocyanines as a pendant group through a ringopening metathesis reaction. The sequential polymerization of two different monomers with (PCy3)2Cl2Ru(d CHC6H5) produced diblock copolymers containing a

Amphiphilic Phthalocyanine Block Copolymers

polymeric phthalocyanine segment and a hydrophilic segment. The aggregation behavior of 8 was investigated by a monolayer experiment at a water-air interface and TEM and AFM measurements. The amphiphilic diblock copolymer 8 formed organized films at the water-air interface by using pure water as the subphase with the phthalocyanine plane in the organized film parallel to the interface. In contrast, 8 in an alkaline aqueous solution formed spherical micelles observed by TEM and AFM. Self-organization of amphiphilic block copolymers containing highly concentrated dye molecules may lead to the formation of higher ordered structures such as rods, spheres, and lamellae. These materials could be used to design nanostructured organic functional materials and should open new possibilities toward the construction of molecular photonic and electronic devices. Experimental Section General Methods. 1H NMR spectra were recorded on a Bruker AVANCE 400 FT-NMR spectrometer operating in CDCl3 solution at 400.13 MHz for 1H. Chemical shifts were relative to internal TMS. Elemental analyses were performed with a PerkinElmer series II CHNS/O analyzer 2400. IR spectra were obtained on a JASCO FS-420 spectrometer as KBr pellets. GPC analyses were carried out with a JASCO HPLC system (pump 1580, UVdetector 1575, refractive index detector 930) with a Showa Denko GPC KF-804L column (8.0 × 300 mm, polystyrene standards, M ) 900-400 000 g/mol) in THF as an eluent at 35 °C (1.0 mL min-1). MALDI-TOF mass spectra were obtained on a PerSeptive Biosystems Voyager DE-Pro spectrometer with dithranol as the matrix. UV-vis spectra were recorded on a JASCO V-570. XRD patterns were measured with Cu KR radiation using a Rigaku Geigerflex. Monolayer Experiment. The monolayer was spread on a triply distilled water subphase (pH ) 7.0) from a solution of 8 in THF at 293 K. The surface pressure-area (π-A) isotherm was recorded 30 min after spreading to allow solvent evaporation and interaction with the subphase. The barrier speed was 10 mm/min. Electron Microscopy. Droplets of 0.01 M NaOH aqueous solution containing polymer 8 (0.02 mg/mL) were placed onto carbon-coated copper grids (400 mesh). The solvent was evaporated in vacuo for 1 h. Electron micrographs were taken on a JEOL JEM-2010 electron microscope at an acceleration voltage of 200 kV. Atomic Force Microscopy. The sample for AFM was obtained by spin-casting a film on a mica substrate from a very dilute aqueous solution of 8 (0.002 mg/mL). The AFM image was recorded in tapping mode, with a SEIKO SPI-3800N at room temperature. Materials. All chemicals were purchased from commercial suppliers and used without purification. All solvents were distilled before each procedure. Adsorption column chromatography was performed using silica gel (Wakogel C-200, 200 mesh). Analytical thin-layer chromatography was performed on commercial Merck plates coated with silica gel 60 F254 or aluminum oxide 60 F254. Compound 3. Potassium carbonate (13.8 g, 0.1 mol), 5-norbornene-2-methanol (3.59 g, 29.0 mmol), and 4-nitrophthalonitrile (5.0 g, 28.9 mmol) were stirred in dry dimethylformamide (DMF) (5 mL) at room temperature under a nitrogen atmosphere for 72 h. The reaction mixture was poured into water (100 mL), and the aqueous layer was extracted with 3 × 30 mL of ethyl acetate. After drying over MgSO4, the organic layer was evaporated and the residue was purified by column chromatography (silica gel, CH2Cl2). Recrystallization from methanol gave white crystals (4.42 g, 61%). 1H NMR (400 MHz, CDCl3): δ ) 7.67-7.71 (m, Ar, 1H), 7.23-7.27 (m, Ar, 1H), 7.13-7.23 (m, Ar, 2H), 5.29-6.23 (m, -CHdCH-, 2H), 3.61-4.15 (m, -OCH2-, 12H), 2.83-3.01 (m, -CH2-, 2H), 1.87-1.97 (m, -CH2-, 2H), 1.22-1.54 (m, -CH2-, 3H). 13C NMR (400 MHz, CDCl3): δ ) 162.2, 138.2, 137.1, 136.0, 135.2, 119.6, 117.5, 107.1, 73.5, 49.5, 45.0, 43.7, 42.2, 41.6, 38.1, 29.6, 28.9. Anal. Calcd for C16H14N2O: C, 76.78; H, 5.64; N, 11.19. Found: C, 76.8; H, 5.6; N, 11.0.

Langmuir, Vol. 18, No. 20, 2002 7687 Compound 1. A mixture of 3 (0.25 g, 1.0 × 10-3 mol), 4-tertbutylphthalonitrile (1.0 g, 5.4 × 10-3 mol), and CuCl2 (0.2 g, 1.5 × 10-3 mol) in 2-(N,N-dimethylamino)ethanol (5 mL) was stirred and slowly heated. Then the mixture was refluxed under N2 for 72 h. After cooling, methanol was added and the precipitate was filtered off. The residue was purified by column chromatography (silica gel, toluene/n-hexane (5:2 v/v)) to afford compound 1 as a blue solid (0.13 g, 15%). TLC: Rf ) 0.30 (toluene/n-hexane (5:2 v/v)). MALDI-TOF-Ms (dithranol): m/z ) 866 ([M + H]+, 100%). Calcd for C52H50N8OCu: 865.3. UV-vis (CH2Cl2): λmax (log ) ) 679(5.29) and 339(4.89). Anal. Calcd for C52H50N8OCu: C, 72.07; H, 5.82; N, 12.93. Found: C, 72.0; H, 5.9; N, 12.8. Compound 2. A solution of Behara’s amine (3.9 g, 9.4 mmol) and triethylamine (3.92 mL, 28.2 mmol) in dry THF (100 mL) was treated with a solution of norborn-2-ene-5-carbonyl chloride16 (1.62 g, 9.4 mmol) in THF (5 mL) and stirred at room temperature for 24 h. The reaction mixture was filtered, and the solvent was evaporated under vacuum to obtain a yellow solid. The solid was purified by column chromatography (silica gel, CH2Cl2/ethyl acetate (10:1 v/v)) to obtain a white solid (2.26 g, 45%). 1H NMR (400 MHz, CDCl3): δ ) 5.98-6.23 (m, -CHdCH-, 2H), 5.70 (s, -NHCO-, 1H), 2.83-3.01 (m, -CH2-, 2H), 2.16-2.24 (m, -CH2-, 6H), 1.88-2.04 (m, -CH2-, 8H), 1.43 (s, -C(CH3)3, 27H), 1.301.38 (m, -CH2-, 3H). 13C NMR (100 MHz, CDCl3): δ )173.5, 138.6, 138.1, 136.1, 132.6, 80.97, 57.65, 50.45, 47.63, 46.70, 45.87, 43.09, 41.91, 30.83, 30.47, 30.22, 28.45. Anal. Calcd for C30H49NO7: C, 67.26; H, 9.22; N, 2.61. Found: C, 67.3; H, 9.1; N, 2.5. General Polymerization Procedure. The norbornene monomer (180.0 µmol) and ruthenium catalyst (PCy3)2Cl2Ru(d CHC6H5) (15.0 mg, 10% mol per norbornene monomer) were dissolved in freshly distilled and degassed toluene (1.0 mL). The solution was stirred at room temperature for 12 h under N2. The reaction mixture was terminated by adding isobutyl vinyl ether (0.1 mL). The resulted poly(norbornene)s 4 and 5 were purified by gel permeation chromatography (Biorad Biobeads SX-1, THF). Compound 4. Yield, 91%. UV-vis (THF): λmax ) 614 and 331 nm. FT-IR (thin film on a NaCl plate): 2953 (-CH2-), 2854 (-CH2-), 1612, 1461, 1376 cm-1. Compound 5. Yield, 98%. 1H NMR (400 MHz, CDCl3): δ ) 5.75 (br, 1H), 5.40 (br, 1H), 5.31 (br, 1H), 3.02 (br, 2H), 2.65 (br, 2H), 2.18 (br, 6H), 1.93 (br, 6H), 1.43 (s, 27H), 1.30 (br, 3H). 13C NMR (100 MHz, CDCl3): δ ) 173.12, 136.34, 125.89 (backbone C-olefin), 80.83, 58.78, 35.5-48.6 (backbone of C-alkyl), 30.71, 30.22, 28.50. FT-IR (thin film on a NaCl plate): 3371 (NH), 2977 (-CH2-), 2874 (-CH2-), 1727 (CdO), 1671 (CdO) cm-1. Preparation of the Diblock Copolymer (6). 2 (0.1 g, 180.0 µmol) was polymerized with (PCy3)2Cl2Ru(dCHC6H5) (15.0 mg, 18.0 µmol) in freshly distilled and degassed toluene (1.0 mL) at room temperature for 1 h under N2. After 1 h, 1 (78.0 mg, 90.0 µmol) in toluene (0.5 mL) was added via a gastight syringe. The vial was sealed, and the reaction mixture was stirred for 1 night at 45 °C. The reaction mixture was terminated by adding isobutyl vinyl ether (0.1 mL). The resulting diblock copolymer 6 was purified by gel permeation chromatography (Biorad Biobeads SX-1, THF). Yield, 58%. UV-vis (THF): 614 and 331 nm. FT-IR (thin film on a NaCl plate): 3383 (NH), 2953 (-CH2-), 2854 (-CH2-), 1730 (CdO), 1674 (CdO), 1614, 1459, 1376 cm-1. Compound 7. Compound 7 was synthesized from 2 and 3 in analogy to the procedure of 6. Yield, 60%. 1H NMR (400 MHz, CDCl3): δ ) 7.18-7.70, 5.39, 5.30, 3.74, 3.10, 2.72, 2.19, 1.94, 1.85, 1.30. 13C NMR (100 MHz, CDCl3): δ ) 173.12, 136.34, 125.89-128.62 (backbone C-olefin), 116.20 (CN), 80.83, 68.32, 57.65, 35.5-48.6 (backbone of C-alkyl), 30.69, 30.18, 29.80, 28.50. FT-IR (thin film on a NaCl plate): 3378 (NH), 2975 (-CH2-), 2933 (-CH2-), 2228 (CN), 1728 (CdO), 1675 (CdO) cm-1. Deprotection Procedure (8). A solution of 6 (30 mg) in 96% formic acid was stirred at room temperature for 1 h. After 1 h, the solvent was removed under a vacuum to obtain a blue solid. The solid was washed with n-hexane before drying. Yield, 98%. UV-vis (THF): 616 and 332 nm. FT-IR (thin film on a NaCl plate): 3371 (NH), 2925 (-CH2-), 2855 (-CH2-), 1716 (CdO), 1647 (CdO), 1541, 1457, 1406 cm-1.

LA020275N