Synthesis of Zeolite as Ordered Multi-Crystal Arrays using Uniformly Aligned Polyurethane as Templates
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Synthesis of Zeolite as Ordered Multi-Crystal Arrays using Uniformly Aligned Polyurethane as Templates Jin Seok Lee, Yun-Jo Lee, Eunju Lee Tae, Yong Soo Park and Kyung Byung Yoon* Department of Chemistry, Sogang University, Seoul 121-742, Korea
ABSTRACT Two types of glass plates coated with uniformly aligned polyurethane films were produced by repeating the cycles of the alternative exposures of the glass plates to 1,4-phenylene diisocyanate (PDI) and 2-butyne-1,4-diol (BDO) and to PDI and terephthalic acid bis-(2-hydroxy ethyl) ester (TBE) for 500 times at elevated temperatures. The glass plates coated with uniformly aligned poly-(PDI-BDO)500 (500 represents the number of the cycle) produced monolayers of closely packed 2D arrays of silicalite-1 crystals with the average size of 370 × 200 × 500 nm on the glass plates upon immersion of the glass plates into a dense gel consisting of tetraethylorthosilicate (TEOS), tetrapropylammonium hydroxide (TPA+OH−), and water (mole ratio = 7:1.5:330) followed by the hydrothermal reaction at 180 °C for 2 h. The silicalite-1 crystals were aligned with the c-axes perpendicular to the substrate plane. Upon switching the polymer from poly-(PDI-BDO)500 to poly-(PDI-TBE)500 the orientations of the silicalite-1 crystals in the 2D arrays changed from c to a axes perpendicular to the substrate. This report therefore demonstrates that the uniformly aligned polyurethane films serve as the templates for the growth of closely packed multi-crystal arrays of silicalite-1 in uniform orientations and the nature of the polyurethane film affects the resulting orientations of the crystals. We propose that the supramolecularly organized organic-inorganic composites consisting of the hydrolyzed organic products and the seed crystals responsible for the above phenomena.
INTRODUCTION Great efforts have been directed at applications of zeolites as advanced materials [1] such as imaging and data storage media [2], light energy harvesting devices [3-5], electrode modifiers [6], and hosts for various materials such as semiconductor quantum dots [7], molecular wires [8], chemical sensors [9], luminescence materials [10], nonlinear optical molecules [11,12], and lasing dyes [13]. One of the essential elements to make such efforts fruitful is to acquire the abilities to organize nano- and microcrystalline zeolite hosts into uniformly aligned and closely packed two- (2D) and three-dimensional (3D) multi-crystal arrays on substrates. The uniformly aligned and closely packed monolayers of microcrystals also bear a great potential to be utilized as excellent seeds for the preparation of uniformly aligned continuous zeolite films, which could be employed as molecular sieve membranes [14]. However, despite a large progress made during the last several decades in the synthesis of new zeolites and the related molecular sieves [15], there have been no synthetic methods for production of uniformly aligned zeolite multi-crystal arrays. We have explored a possible post synthetic route to the production of orde
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