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Langmuir 2004, 20, 484-490
Supramolecular Self-Assembly of Inclusion Complexes of a Multiarm Hyperbranched Polyether with Cyclodextrins Xinyuan Zhu,*,† Liang Chen,† Deyue Yan,*,† Qun Chen,‡ Yefeng Yao,‡ Yan Xiao,† Jian Hou,† and Jingye Li† Institute of Polymer Materials, College of Chemistry and Chemical Technology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People’s Republic of China, and Analytical Center and The Key Laboratory of Education Ministry for Optical and Magnetic Resonance Spectroscopy, East China Normal University, Shanghai 200062, People’s Republic of China Received September 17, 2003. In Final Form: October 13, 2003 A new class of crystalline inclusion complexes of a multiarm hyperbranched polyether combined with various cyclodextrins (CDs) was successfully prepared. Using self-condensing ring-opening polymerization, a kind of multiarm polyether with a hyperbranched poly(3-ethyl-3-oxetanemethanol) core and multiple linear poly(ethylene glycol) (PEG) arms was obtained. It has been found that this kind of hyperbranched polyether can be dissolved in water. Adding R-CDs to the multiarm hyperbranched polyether solution, molecular recognition results in the formation of crystalline inclusion complexes based on the noncovalent interactions between the linear PEG arms of the polyether particles and the R-CDs. These multiarm polyether inclusion complexes have been well characterized. Interestingly, quite different from inclusion complexes of CDs and linear polymeric guests, the complexes of the multiarm hyperbranched polyether with R-CDs show a novel lamellar morphology. The experimental results validate that the resultant lamellar crystals have a juxtaposed structure. In addition, the formation mechanism of these inclusion complexes of a multiarm polyether with R-CDs has also been well described. Besides the role of displacement of associated water molecules and the presence of hydrogen bonding between CDs in channel structure CD inclusion complexes, the noncovalent intermolecular forces between CDs and polymers also play an important role in the formation of complex architectures.
Introduction Supramolecular chemistry has made great progress over the past quarter century.1,2 Different from molecular chemistry based on covalent bonds, supramolecular chemistry aims at developing highly complex chemical systems from components interacting through noncovalent intermolecular forces.1 In recent years, the use of molecular recognition in the design of self-assembling systems consisting of cyclodextrins and guest molecules has attracted increasing attention.3 Cyclodextrins (CDs) are a group of structurally related cyclic oligosaccharides consisting of several (6-(R), 7-(β), and 8-(γ)) glucopyranose units connected by R-1,4-glucoside links. It is well-known that CDs can form inclusion complexes with a wide variety of low molecular weight compounds, including both * To whom correspondence should be addressed. Tel.: +86-2154742665. Fax: +86-21-54741297. E-mail address: xyzhu@ sjtu.edu.cn (Xinyuan Zhu) and
[email protected] (Deyue Yan). † Shanghai Jiao Tong University. ‡ East China Normal University. (1) Lehn, J.-M. Supramolecular Chemistry: Concepts and Perspectives; Wiley-VCH: Weinheim, 1995. Lehn, J.-M. Science 2002, 295, 2400. Lehn, J.-M. Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 4763. (2) Discher, D. E.; Eisenberg, A. Science 2002, 297, 967. Percec, V.; Ahn, C.-H.; Ungar, G.; Yeardley, D. J. P.; Mo¨ller, M.; Sheiko, S. S. Nature 1998, 391, 61. Menger, F. M.; Balachander, N. J. Am. Chem. Soc. 1992, 114, 5862. Menger, F. M.; Lee, S. S. J. Am. Chem. Soc. 1994, 116, 5987. Ringsdorf, H.; Simon, J. Nature 1994, 371, 284. Ringsdorf, H.; Schlarb, B.; Venzmer, J. Angew. Chem., Int. Ed. Engl. 1988, 27, 113. Whitesides, G. M.; Grzybowski, B. A. Science 2002, 295, 2418. Whitesides, G. M.; Boncheva, M. Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 4769. (3) Jullien, L.; Canceill, J.; Valeur, B.; Bardez, E.; Lefavre, J.-P.; Lehn, L.-M.; Marchi-Artzner, V.; Pansu, R. J. Am. Chem. Soc. 1996, 11, 5432. Breslow, R.; Chung, S. J. Am. Chem. Soc. 1996, 11, 5432. Li, G.; McGown, L. B. Science 1994, 264, 249. Uekama, K.; Hirayama, F.; Irie, T. Chem. Rev. 1998, 98, 2045.
inorganic and organic molecules.4 In 1990, Harada et al.5 first reported the formation of complexes of CDs with polymers. Due to their novel architectures and important applications in the biomedical fields, inclusion complexes of CDs and polymers have been extensively studied.6-13 Most investigations are focused on the preparation and (4) Szejtli, J. Cyclodextrins and Their Inclusion Complexes; Akademiai Kiado: Budapest, 1982. Bender, M. L.; Komiyama, M. Cyclodextrin Chemistry; Springer-Verlag: Berlin, 1978. Saenger, W. Angew. Chem., Int. Ed. Engl. 1980, 19, 344. Harada, A.; Takahashi, S. J. Chem. Soc., Chem. Commun. 1984, 645. Colquhoun, H. M.; Stoddard, J. F.; Williams, D. J. Angew. Chem., Int. Ed. Engl. 1986, 25, 487. (5) (a) Harada, A.; Kamachi, M. Macromolecules 1990, 23, 2821. (b) Harada, A.; Kamachi, M. J. Chem. Soc., Chem. Commun. 1990, 1322. (6) Harada, A.; Li, J.; Kamachi, M. Nature 1992, 356, 325. Harada, A.; Li, J.; Kamachi, M. Nature 1993, 364, 516. Harada, A.; Li, J.; Kamachi, M. Macromolecules 1993, 26, 5698. Harada, A.; Li, J.; Kamachi, M. Nature 1994, 370, 126. Harada, A.; Li, J.; Kamachi, M. J. Am. Chem. Soc. 1994, 116, 3192. Harada, A.; Nishiyama, T.; Kawaguchi, Y.; Okada, M.; Kamachi, M. Macromolecules 1997, 30, 7115. Harada, A.; Nishiyama, T.; Kawaguchi, Y.; Okada, M.; Kamachi, M. Macromolecules 2000, 33, 4472. Okumura, H.; Kawaguchi, Y.; Harada, A. Macromolecules 2001, 34, 6338. (7) Wenz, G.; Keller, B. Angew. Chem., Int. Ed. Engl. 1992, 31, 197. Klyamkin, A. A.; Topchieva, I. N.; Zubov, V. P. Colloid Polym. Sci. 1995, 273, 520. Steinbrunn, M. B.; Wenz, G. Angew. Chem., Int. Ed. Engl. 1996, 35, 2139. Hermann, W.; Keller, B.; Wenz, G. Macromolecules 1997, 30, 4966. Weickenmeier, M.; Wenz. G. Macromol. Rapid Commun. 1997, 18, 1109. Yoshida, K.; Shimomura, T.; Ita, K.; Hayakawa, R. Langmuir 1999, 15, 910. (8) Born, M.; Ritter, H. Makromol. Chem. Rapid Commun. 1991, 12, 471. Born, M.; Koch, T.; Ritter, H. Acta Polym. 1994, 45, 68. Born, M.; Koch, T.; Ritter, H. Macromol. Chem. Phys. 1995, 196, 1761. Born, M.; Ritter, H. Angew. Chem. 1995, 107, 342. Noll, O.; Ritter, H. Macromol. Rapid Commun. 1997, 18, 53. Noll, O.; Ritter, H. Macromol. Chem. Phys. 1998, 199, 791. Ritter, H.; Sadowski, O.; Tepper, E. Angew. Chem., Int. Ed. Engl. 2003, 42, 3171. (9) Born, M.; Ritter, H. Angew. Chem., Int. Ed. Engl. 1995, 34, 309. Born, M.; Ritter, H. Adv. Mater. 1996, 8, 149. (10) Topchieva, I. N.; Gerasimov, V. I.; Panova, I. G.; Karezin, K. I.; Efremova, N. V. Polym. Sci., Ser. A 1998, 40, 171. Jiao, H.; Goh, S. H.; Valiyaveettil, S. Macromolecules 2002, 35, 1980.
10.1021/la035740a CCC: $27.50 © 2004 American Chemical Society Published on Web 12/10/2003
Self-Assembly of Inclusion Complexes
characterization of main-chain polyrotaxanes in which the linear polymeric guests pass through a number of CDs to form the inclusion complexes.5-7 On the other hand, Ritter et al.8 succeeded in preparing side-chain polyrotaxanes. Moreover, Born and Ritter9 went further and synthesized tandem polyrotaxanes, in which each branched polymeric side chain has a noncovalently bound cyclodextrin at either end of the side chain. Recently, Topchieva and Goh have also prepared inclusion complexes using star-shaped polymers and CDs.10 Although much work concerning highly branched polymers (dendrimer or hyperbranched polymer) as covalently bound modifiers for CDs have been reported,14 to our knowledge, there has been no study dealing with crystalline inclusion complexes between highly branched polymers and CDs formed through noncovalent interactions. Furthermore, most investigations on CD-based complexes are focused on the preparation and characterization of inclusion complexes between polymers and CDs, and little attention has been paid to the structural changes that occur during the formation process. In fact, thorough research into the complex formation process helps us understand the complexity of supramolecular systems. Our laboratory has investigated crystalline inclusion complexes of CDs with some polyethers, and first found that all R-, β-, and γ-CDs are able to form crystalline inclusion complexes with poly(1,3-dioxolane).12 By changing the architecture of the polyether, new inclusion complexes can be designed. Recently, we utilized selfcondensing ring-opening polymerization to synthesize a new kind of multiarm hyperbranched polyether.15 It has been found in this work that this hyperbranched polyether is readily soluble in water and forms a stable random-coil solution. Therefore, it is very interesting to observe what happens in solution after introducing another component, such as a CD, which interacts with the polymer via specific noncovalent interactions. In the present work, a new class of polyether-based semipolyroxatanes, multiarm inclusion complexes with hyperbranched cores, are prepared, and the inclusion complexation and supramolecular selfassembly processes are thoroughly discussed. It will be shown that the noncovalent intermolecular forces between CDs and polymers play a very important role in the formation of complex architectures. (11) Huang, L.; Allen, E.; Tonelli, A. E. Polymer 1998, 39, 4857. Rusa, C. C.; Tonelli, A. E. Macromolecules 2000, 33, 1813. Rusa, C. C.; Luca, C.; Tonelli, A. E. Macromolecules 2001, 34, 1318. Yamaguchi, I.; Osakada, K.; Yamamoto, T. J. Am. Chem. Soc. 1996, 118, 1811. Udachin, K. A.; Wilson, L. D.; Ripmeester, J. A. J. Am. Chem. Soc. 2000, 122, 12375. Ooya, T.; Mori, H.; Terano, M.; Yui, N. Macromol. Rapid Commun. 1995, 16, 259. Huh, K. M.; Ooya, T.; Sasaki, S.; Yui, N. Macromolecules 2001, 34, 2402. (12) Li, J.; Yan, D. Macromolecules 2001, 34, 1542. Li, J.; Yan, D. Macromol. Chem. Phys. 2002, 203, 155. Li, J.; Yan, D.; Jiang, X.; Chen, Q. Polymer 2002, 43, 2625. (13) Panova, I. G.; Gerasimov, V. I.; Kalashnikov, F. A.; Topchieva, I. N. Polym. Sci., Ser. B 1998, 40, 415. Li, J.; Yan, D.; Chen, Q. Sci. China, Ser. B: Chem., Life Sci., Earth 2002, 32, 51. (14) Newkome, G. R.; Godı´nez, L. A.; Moorefield, C. N. Chem. Commun. 1998, 1821. Gonza´lez, B.; Casado, C. M.; Alonso, B.; Cuadrado, I.; Mora´n, M.; Wang, Y.; Kaifer, A. E. Chem. Commun. 1998, 2569. Ortega-Caballero, F.; Gime´nez-Martı´nez, J. J.; Garcı´a-Fuentes, L.; OrtizSalmero´n, E.; Santoyo-Gonza´lez, F.; Vargas-Berenguel, A. J. Org. Chem. 2001, 66, 7786. Fulton, D. A.; Stoddart, J. F. Bioconjugate Chem. 2001, 12, 655. Suh, J.; Hah, S. S.; Lee, S. H. Bioorg. Chem. 1997, 25, 63. (15) Sunder, A.; Hanselmann, R.; Frey, H.; Mu¨lhaupt, R. Macromolecules 1999, 32, 4240. Stiriba, S.-E.; Kaultz, H.; Frey, H. J. Am. Chem. Soc. 2002, 124, 9698. Bednarek, M.; Biedron, T.; Helinski, J.; Kaluzynski, K.; Kubisa, P.; Penczek, S. Macromol. Rapid Commun. 1999, 20, 369. Magnusson, H.; Malmstrom, E.; Hult, A.; Macromol. Rapid Commun. 1999, 20, 453. Hou, J.; Yan, D.; Zhu, X.; Fang, Y. Chem. J. Chin. Univer. 1999, 20, 1815. Yan, D.; Hou, J.; Zhu, X.; Kosman, J. J.; Wu, H. S. Macromol. Rapid Commun. 2000, 21, 557.
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Experimental Section a. Synthesis of 3-Ethyl-3-oxetanemethanol. 3-Ethyl-3oxetanemethanol (1) was prepared from trimethylolpropane according to ref 16.16 Yield: 93.5%; Anal. Calcd for C6H12O2: C, 62.07; H, 10.34; O, 27.59. Found: C, 62.00; H, 10.68; O, 27.32. 1H NMR (500 MHz, DMSO-d ): δ ) 0.81 (s, 3H; -CH ), 1.60 (m, 6 3 2H; -CH2CH3), 3.48 (m, 2H; -CH2OH), 4.17, 4.27 (2m, 4H; -CH2OCH2-), 4.80 (m, 1H; -OH). IR υ (cm-1): 3412.5 (O-H), 2957, 2873 (C-H), 1049 (C-O), 975.5 (C-O-C). b. Synthesis of Hyperbranched Poly(3-ethyl-3-oxetanemethanol). The hyperbranched poly(3-ethyl-3-oxetanemethanol) (2) was prepared by self-condensing ring-opening polymerization.15 The cationic polymerization of monomer 1 was directly initiated by BF3‚OEt2, and the reaction was carried out under nitrogen in a three-necked round-bottomed flask with a PTFE stirrer and a funnel. Prior to the reaction, the system was degassed using nitrogen for 15 min, and the catalyst BF3‚OEt2 (0.05 mol) and solvent C2H4Cl2 (20 mL) were then added. The reaction vessel was placed in an ice-salt bath and monomer 1 (0.1 mol) was introduced through the funnel. After 24 h the crude product 2 was precipitated into distilled water and immersed for 48 h. Finally, the resulting solid was obtained by filtration and then dried at 110 °C. Yield: 92%; Molecular weight determination: vapor pressure osmometry, Mn ) 9170; gel permeation chromatography (GPC), Mn ) 10500, Mw ) 16500. 1H NMR (500 MHz, DMSO-d6): δ 0.8 (m, -CH3), 1.25 (m, -CH2CH3), 3.13, 3.19, 3.23 (3m, -CH2OCH2-, three signals from the linear, dendritic and terminal repeating units), 3.28 (m, -CH2OH), 4.15 (m, -OH). 13C NMR (75.47 MHz, TMS): δ 7.6 (-CH2CH3), 21.38, 22.31, 23.08 (-CH2CH3, three signals from the terminal, linear, and dendritic repeating units), 43 (>CC
