3972 Langmuir 1999, 15, 3972-3980 Chromatic Studies of a Polymerizable Diacetylene Hydrogen Bonding Self-Assembly: A “Self-Folding” Process To Explain the Chromatic Changes of Polydiacetylenes Qun Huo, K. C. Russell,† and Roger M. Leblanc* Center for Supramolecular Science, Department of Chemistry, University of Miami, P.O. Box 249118, Coral Gables, Florida 33124 Received January 11, 1999. In Final Form: March 9, 1999 In the present study, a new diacetylene compound (PDATAZ), which readily forms a complementary hydrogen bonding self-assembly at the air-water interface or in the solid state with barbituric acid (BA) or cyanuric acid (CA), was designed and synthesized. The photopolymerization studies of PDATAZ and its assembly with BA or CA have revealed some important insights on the chromatic properties of polydiacetylenes. It was found that the chromatic property of polydiacetylenes is determined by whether the polymer chain is capable of adopting a linear chainlike shape. With the continuous increase of the length of the polymer chain, the original linear polyenyne backbone starts to “self-fold” to a “zigzag” structure due to the free rotation of single bonds within the polymer chain. The efficient π-electron delocalization along the polyenyne backbone is interrupted by this process, leading to a chromatic change from the blue to red form of polydiacetylenes. If there are strong intermolecular interactions existing between the polar groups of the side chains, such as the complementary hydrogen bonding network between the triaminotriazine (TAZ) moiety of the diacetylene amphiphile and its complementary components, the movement of the side chains is restricted and the folding process of the polymer backbone is inhibited. The polymer backbone is able to maintain its extended chainlike conformation, leading to only the blue form absorption band. Introduction triazine (TAZ) amphiphiles bearing C12 or C18 side chains (2C TAZ or 2C TAZ) form highly organized 1:1 hydrogen- Among the different intermolecular interactions (e.g. 12 18 bonded networks at the air-water interface with comple- electrostatic, hydrogen bonding, van der Waals, and π-π mentary components such as barbituric acid (BA), cyanuric stacking), the strength, directionality, and selectivity of acid (CA), or barbital (BT) from the aqueous subphase.3,4 hydrogen bonding places it at the center of many research AC alkyl chain modified barbituric acid lipid was found efforts aimed at the design of supermolecules and crystal 18 to form a hydrogen bonding network at the interface with engineering.1 As one notable example, the complementary a complementary triaminopyrimidine, as well.5 While hydrogen bonding self-assembly between melamine and Langmuir and Langmuir-Blodgett film techniques have barbiturates or cyanurates in the solid state and solution been important methods to produce highly organized has caused extensive attention.2 Through complementary structures in 2-D complementary to 3-D crystal engineer- hydrogen bonding between one component that has a ing, these studies open an important new approach to the “donor-acceptor-donor” triad and another component design of supermolecules in 2-D. that has a complementary “acceptor-donor-acceptor” array, highly organized supramolecular structures, such Polydiacetylenes are the most widely investigated class as linear tapes, crinkle tapes, or rosettes, are formed when of conjugated polymers for third-order nonlinear optical effects,6 since their preparation was first reported in 1969 these components are mixed. 7 More recently, it has been shown that hydrogen bond by Wegner. Diacetylenes substituted with various side - chains readily undergo photopolymerization to form an directed self-assembly at the air water interface is as - efficient as that in nonpolar organic solvent. Triamino- ene yne alternated polymer chain upon UV irradiation (254 nm) in a wide range of organized structures, such as single crystals,8 Langmuir-Blodgett films,9 self-as- * To whom correspondence may be addressed. Tel: 305-284- 10 11 2282. Fax: 305-284-4571. E-mail: [email protected]. sembled monolayers, liposomes or vesicles, and solu- † Tel: 305-284-6857. E-mail: [email protected]. (1) Lehn, J.-M. Supramolecular Chemistry; VCH: New York, 1995. (3) (a) Honda, Y.; Kurihara, K.; Kunitake, T. Chem. Lett. 1991, 681- (2) (a) Zerkowski, J. A.; Seto, C. T.; Weirda, D. A.; Whitesides, G. M. 684. (b) Koyano, H.; Yoshihara, K.; Ariga, K.; Kunitake, T.; Oishi, Y.; J. Am. Chem. Soc. 1990, 112, 9025-9026. (b) Zerkowski, J. A.; Seto, C. Kawano, O.; Kuramori, M.; Suehiro, K. J. Chem. Soc., Chem. Commun. T.; Whitesides, G. M. J. Am. Chem. Soc. 1992, 114, 5473-5475. (c) Seto, 1996, 1769-1770. (c) Koyano, H.; Bissel, P.; Yoshihara, K.; Ariga, K.; C. T.; Whitesides, G. M. J. Am. Chem. Soc. 1993, 115, 905-916. (d) Kunitake, T. Chem. Eur. J. 1997, 3, 1077-1082. (d) Marchi-Artzner, Zerkowski, J. A.; Whitesides, G. M. J. Am. Chem. Soc. 1994, 116, 4298- V.; Artzner, F.; Karthaus, O.; Shimomura, M.; Ariga, K.; Kunitake, T.; 4304. (e) Zerkowski, J. A.; McDonald, J. C.; Seto, C. T.; Wierda, D. A.; Lehn, J.-M. Langmuir 1998, 14, 5164-5171. Whitesides, G. M. J. Am. Chem. Soc. 1994, 116, 2382-2391. (f) (4) Huo, Q.; Russell, K. C.; Leblanc, R. M. Langmuir 1998, 14, 2174- Zerkowski, J. A.; Mathias, J. P.; Whitesides, G. M. J. Am. Chem. Soc. 2186. 1994, 116, 5305-5315. (g) Zerkowski, J. A.; McDonald, J. C.; Whitesides, (5) (a) Ahuja, R.; Caruso, P. L.; Mo¨bius, W. P.; Ringsdorf, H.; Wildburg, G. M. Chem. Mater. 1994, 6, 1250-1257. (h) Mathias, J. P.; Simanek, G. Angew. Chem., Int. Ed. Engl. 1993, 32, 1033-1036. (b) Bohanon, T. E. E.; Zerkowski, J. A.; Seto, C. T.; Whitesides, G. M. J. Am. Chem. Soc. M.; Denzinger, S.; Fink, R.; Paulus, W.; Ringsdorf, H.; Weck, M. Angew. 1994, 116, 4316-4325. (i) Mathias, J. P.; Seto, C. T.; Simanek, E. E.; Chem., Int. Ed. Engl. 1995, 34,58-60. (c) Weck, M.; Fink, R.; Ringsdorf, Whitesides, G. M. J. Am. Chem. Soc. 1994, 116, 1725-1736. (j) Russell, H. Langmuir 1997, 13, 3515-3522. K. C.; Leize, E.; Van Dorsselaer, A.; Lehn, J.-M. Angew. Chem., Int. Ed. (6) Prasad, P. N.; Williams, D. J. Introduction to Nonlinear Optical Engl. 1995, 34, 209-213. (k) Drain, C. M.; Russell, K. C.; Lehn, J. M. Effects in Molecules & Polymers; John Wiley & Sons: New York, 1991; Chem. Commun. 1996, 337-338. (l) Russell, K. C.; Lehn, J.-M.; pp 231-235. Kyritsakas, N.; DeCian, A.; Fisher, J. New. J. Chem. 1998, 123-128. (7) Wegner, G. Z. Naturforsch. 1969, 24B, 824-832. 10.1021/la990025f CCC: $18.00 © 1999 American Chemical Society Published on Web 04/30/1999 Diacetylene Hydrogen-Bonding Self-Assembly Langmuir, Vol. 15, No. 11, 1999 3973 Figure 1. Illustration of the hydrogen bonding network formed between PDATAZ and BA at the air-water interface. tions.12 The one-dimensional conjugated polyenyne back- and synthesized. It is expected that this amphiphile also bone exhibits large nonlinear optical susceptibilities forms 1:1 hydrogen bonding networks with BA or CA from comparable to inorganic semiconductors with ultrafast the aqueous subphase, as shown in Figure 1, like other response time.6,13 The conjugated polydiacetylene back- triaminotriazine amphiphiles.3,4 The effect of the formation bone has two spectroscopically distinct phases, designated of such a highly organized network structure on the as the blue and the red forms, that result from their exciton photopolymerization of diacetylenes has been examined absorption peaks at ca. 640 and 540 nm, respectively.14 both at the air-water interface and in the solid state. Under external perturbation, such as heat 15 or mechanical These studies have led to a revisiting and novel inter- stress,16 the conjugated polyenyne backbone can undergo pretation of the chromatic properties of polydiacetylenes. a drastic reversible color transition or irreversible color change from the blue to the red form. This unique Experimental Section chromatic property has made polydiacetylenes promising Materials. Cyanuric chloride, ethylenediamine, barbituric candidates in the development of biosensors.17 acid (99%), and cyanuric acid (98%) were purchased from Aldrich The present study has attempted to reveal the effect Chemical Co. and used in organic synthesis or monolayer studies of a complementary hydrogen bonding network on the directly. 10,12-Pentacosadiynoic acid (PDA) was purchased from GSF Chemical Co. (Powell, OH) and recrystallized from petroleum photopolymerization and chromatic properties of ether before use. All organic solvents for the synthesis and polydiacetylenes. A polymerizable diacetylene compound purification were purchased from Fisher Scientific Co. as reagent (PDATAZ), in which two hydrophobic 10,12-penta- grade and were used without further purification. 2-Amino-4,6- cosadiynoic acid (PDA) chains are attached to a TAZ dichloro-1,3,5-triazine was prepared from cyanuric chloride and headgroup through ethylenediamine linkers, was designed anhydrous ammonia according to the literature.2e (10,12-Pen- tacosadiyn amido)ethylamine was prepared from the succina- (8) (a) Donovan, K. J.; Wilson, E. G. Synth. Met. 1989, 28, D563- midyl ester of 10,12-pentacosadiynoic acid and ethylenediamine.11b D568. (b) Koshihara, S.; Tokura, Y.; Takeda, K.; Koda, T.; Kobayashi, The 1H (400 MHz) and 13C (100 MHz) NMR spectra were obtained A. J. Chem. Phys. 1990, 92, 7581-7588. (c) Tashiro, K.; Nishimura, H.; from a Varian VXR 400 MHz spectrometer. High-resolution mass Kobayashi, M. Macromolecules 1996, 29, 8188-8196. (d) Itoh, C.; spectra were conducted by the University of Illinois, School of - Kondoh, T.; Tanimura, K. Chem. Phys. Lett. 1996, 261, 191 194. Chemical Sciences. Melting points were taken on a Thomas- (9) (a) Tieke, B.; Graf, H. J.; Wegner, G.; Naegele, B.; Ringsdorf, H.; Banerjie, A.; Day, D.; Lando, J. B. Colloid Polym. Sci. 1977, 255, 521- Hoover melting point apparatus and are uncorrected.