Langmuir 2008, 24, 1617-1620
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Facile Preparation of Macroscopic Soft Colloidal Crystals with Fiber Symmetry Shanshan Hu,† Yongfeng Men,*,† Stephan V. Roth,‡ Rainer Gehrke,‡ and Jens Rieger§ State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Graduate School of Chinese Academy of Sciences, Renmin Street 5625, 130022 Changchun, People’s Republic of China, HASYLAB am DESY, Notkestrasse 85, 22607 Hamburg, Germany, and BASF Aktiengesellschaft, Polymer Physics, 67056 Ludwigshafen, Germany ReceiVed October 25, 2007. In Final Form: January 2, 2008 A facile, efficient way to fabricate macroscopic soft colloidal crystals with fiber symmetry by drying a latex dispersion in a tube is presented. A transparent, stable colloidal crystal was obtained from a 25 wt % latex dispersion by complete water evaporation for 4 days. The centimeter-long sample was investigated by means of synchrotron small-angle X-ray diffraction (SAXD). Analysis of a large number of distinct Bragg peaks reveals that uniaxially oriented colloidal crystals with face-centered cubic lattice structure were formed. The measurement of evaporation rates under different conditions indicates that the water evaporates primarily through the optically clear regions (i.e., via the solid material) even when the region is more than 2 mm thick.
Introduction Colloidal crystals are attracting significant attention because of their potential applications in photonic band gap materials, optical filters, color films, and so forth.1-3 Hard-sphere colloidal crystals have been investigated by many researchers using light scattering,4,5 small-angle neutron scattering,6 and SAXD.7,8 There have also been many investigations on soft polymeric colloidal crystals.9,10 Unlike the case of hard-sphere colloidal crystals where randomly stacked hexagonal close packing is found, soft colloidal crystals formed from charged particles normally exhibit an fcc structure.11-13 The growth of 2-D and 3-D polymer colloidal crystals on substrates has been studied by many groups.11,14-17 Single crystals can be obtained by the use of electric fields18 or * Corresponding author. E-mail:
[email protected]. † Changchun Institute of Applied Chemistry. ‡ HASYLAB am DESY. § BASF Aktiengesellschaft. (1) Blanco, A.; Chomski, E.; Grabtchak, S.; Ibisate, M.; John, S.; Leonard, S. W.; Lopez, C.; Meseguer, F.; Miguez, H.; Mondia, J. P.; Ozin, G. A.; Toader, O.; van Driel, H. M. Nature 2000, 405, 437-440. (2) Tarhan, I. I.; Watson, G. H. Phys. ReV. Lett. 1996, 76, 315-318. (3) Xu, H.; Yi, T.; Leyrer, R. J.; Rieger, J. Polym. Bull. 2006, 57, 785-796. (4) Pusey, P. N.; van Megen, W.; Bartlett, P.; Ackerson, B. J.; Rarity, J. G.; Underwood, S. M. Phys. ReV. Lett. 1989, 63, 2753-2756. (5) Martelozzo, V. C.; Schofield, A. B.; Poon, W. C. K.; Pusey, P. N. Phys. ReV. E 2002, 66, 021408. (6) Versmold, H.; Lindner, P. Langmuir 1994, 10, 3043-3045. (7) Petukhov, A. V.; Aarts, D. G. A. L.; Dolbnya, I. P.; de Hoog, E. H. A.; Kassapidou, K.; Vroege, G. J.; Bras, W.; Lekkerkerker, H. N. W. Phys. ReV. Lett. 2002, 88, 208301. (8) Vos, W. L.; Megens, M.; van Kats, C. M.; Bosecke, P. Langmuir 1997, 13, 6004-6008. (9) Keddie, J. L. Mater. Sci. Eng. R 1997, 21, 101-170. (10) Winnik, M. A. Curr. Opin. Colloid Interface Sci. 1997, 2, 192-199. (11) Chevalier, Y.; Pichot, C.; Graillat, C.; Joanicot, M.; Wong, K.; Maquet, J.; Lindner, P.; Cabane, B. Colloid Polym. Sci. 1992, 270, 806-821. (12) Rieger, J.; Hadicke, E.; Ley, G.; Lindner, P. Phys. ReV. Lett. 1992, 68, 2782-2785. (13) Men, Y. F.; Rieger, J.; Roth, S. V.; Gehrke, R.; Kong, X. M. Langmuir 2006, 22, 8285-8288. (14) Tang, Y.; Malzbender, R. M.; Mockler, R. C.; O’Sullivan, W. J; Beall, J. A. J. Phys. A: Math. Gen. 1987, 20, L189-L192. (15) Denkov, N. D.; Velev, O. D.; Kralchevsky, P. A.; Ivanov, I. B.; Yoshimura, H.; Nagayama, K. Langmuir 1992, 8, 3183-3190. (16) Adachi, E.; Dimitrov, A. S.; Nagayama, K. Langmuir 1995, 11, 10571060. (17) Jiang, P.; Bertone, J. F.; Hwang, K. S.; Colvin, V. L. Chem. Mater 1999, 11, 2132-2140. (18) Yethiraj, A.; Thijssen, J. H. J.; Wouterse, A.; van Blaaderen, A. AdV. Mater. 2004, 16, 596-600.
templates.19 Synthesizing large single crystals with adjustable crystal orientation is one of the big challenges for the application of colloidal crystals.19,20 Colloidal crystals of circular symmetry have been produced using capillaries,21,22 and even colloidal crystals formed in microscopic 1-D channels have been realized.23 Here we show that rate-controlled evaporation of water from a soft polymeric latex dispersion in a tube yields transparent, stable fcc colloidal crystals with overall fiber symmetry. The glass-transition temperature of the polymeric latex particles is around or below room temperature, implying that the latex particles deform during solidification into polyhedra. To our knowledge, no soft-sphere colloids with similarly oriented crystals have been described in the past. Our approach provides an easy new way to produce axially oriented colloidal crystals. Experimental Section A styrene/n-butyl acrylate copolymer (PS-co-BA, Tg ) 20 °C) with about 50% by weight of each monomer and the latex dispersion with a solid content of ca. 25 wt % is used in this study. It is a commercially available raw material for coating and adhesion applications produced by BASF China. The system is stabilized against coagulation by negative surface charges on the latex particles originating from sulfate groups. The dispersion contains additional emulsifier and electrolyte. The particle size distribution was quite narrow. The mean diameter of the latex particles is 118 nm as determined by light scattering. The weight loss during solidification was measured by an analytic balance (BT 25S, Sartorius, Germany) with a precision of 0.01 mg. The 25 wt % dispersion was dried in glass tubes with a diameter of 1.5 mm and a length of about 30 mm at room temperature (25 ( 1 °C). The density of the dried latex is 1.08 g/cm3. To obtain a high scattering intensity in SAXD experiments, we used the Kapton tube in some cases instead of the glass tube. Glass tubes and Kapton tubes yield identically oriented crystals. The latex was dried in a Kapton tube with a diameter of about 2 mm and a length of 40 mm at 25 ( 1 °C and relative (19) van Blaaderen, A.; Ruel, R.; Wiltzius, P. Nature 1997, 385, 321-324. (20) Palberg, T.; Monch, W.; Schwarz, J.; Leiderer, P. J. Chem. Phys. 1995, 102, 5082-5087. (21) Abkarian, M.; Nunes, J.; Stone, H. A. J. Am. Chem. Soc. 2004, 126, 5978-5979. (22) Kamp, U.; Kitaev, V.; von Freymann, G.; Ozin, G. A.; Mabury, S. A. AdV. Mater. 2005, 17, 438-443. (23) Li, F.; Badel, X.; Linnros, J.; Wiley, J. B. J. Am. Chem. Soc. 2005, 127, 3268-3269.
10.1021/la703332v CCC: $40.75 © 2008 American Chemical Society Published on Web 01/24/2008
1618 Langmuir, Vol. 24, No. 5, 2008
Letters
Figure 1. Series of photographs of a 25 wt % latex dispersion drying in a glass tube taken at different times (left). The number indicated on each photograph denotes the drying time in hours. Weight loss as a function of time during water evaporation under three conditions (right): both sides of the tube left open (a); tube sealed on the dispersion side after being dried for 6 h (b); and tube sealed on the solid side after being dried for 6 h (c). The insets show the corresponding photographs under these conditions after the system had been dried for 48 h. The sealing film around tube c was peeled off for the sake of clarity. humidity
