Preparation Of Functional Ordered Honeycomb-Patterned Films Via Breath Figures

Ordered microporous structures have attracted considerable attention recently due to their potential applications in diverse areas such as membranes, photonic or optoelectronic devices, and catalysis. Among those techniques for the preparation of microporous films with submicro- and nano-meter scales, the breath figure method is proved to be an effective dynamic template method through providing a humid condition to the surface of polymer solution in a volatile solvent and has been extensively applied because of its facility, speediness and economy. Normally, stabilization of the condensed water droplets is essential for the patterned structure to achieve high regularity, which seriously limits the materials applied for this method. Therefore, to integrate diverse functions into patterned structures, development of new materials is essential, with recent attention concentrated on the functional patterns of nanomaterials and biomaterials with unique optical, magnetic, and biological properties.Firstly, we have prepared self-organized microporous films based on a series of surfactant–encapsulated polyoxometalate complexes (SEPs) by using ordered condensed droplets as a template. The film shows a three-dimensional microporous structure, in which the top surface shows a highly ordered honeycomb structure. We have systematically investigated the influence of SEPs'alkyl chain density, length and SEPs'size on the formation of honeycomb structures. The proper hydrophobicity of SEPs was proposed to be an essential factor for the formation of honeycomb films, and large-sized SEPs are favorable for the fabrication of highly ordered honeycomb structures. The conditions for the formation of different surface morphologies have been discussed in terms of the contact angle of SEPs at the interface between water and chloroform, and a contact angle slightly greater than 90o is found to be pre-requisite for the formation of honeycomb structures. The results not only help to further comprehend the mechanism of the formation of honeycomb structures, but also provide some guidance for the design of ordered microporous films based on organic/inorganic hybrid materials.Secondly, surfactant-encapsulated polyoxometalate complex, (DODA)9[EuW10O36] (DODA/EuW10), is applied to functionalize the breath figure holes of polystyrene (PS) film via a straightforward, one-step process by doping DODA/EuW10 into PS solution. Accompanied with the self-organization of the water droplets, amphiphilic DODA/EuW10 is found to self-assemble at the PS solution–water droplet interface to stabilize the water droplets, and it effectively enhances the order of the PS microporous film. Highly ordered PS microporous film in which DODA/EuW10 accumulates on the internal surfaces of the holes with an ordered and tight lamellar structure was obtained. The film exhibits intense red emission in ultraviolet light and can be worked as the self-supporting film owing to the well maintenance of the original fluorescence of DODA/EuW10 and the good processibility of PS. Furthermore, on the basis of the obtained SEPs functionalized PS microporous film, Ag and Fe2O3 nanoparticles have been successfully introduced into the microporous structure, respectively, by adopting suitable ways.Furthermore, we have extended the breath figure method to Mn12 and DNA areas. We have constructed the Mn12-based magnetic ordered honeycomb structures through the modification of fatty acids to Mn12 clusters. Importantly, the single–molecule magnetic property of the Mn12 complex is well maintained in the honeycomb-patterned film which can be effectively used as a permanent information storage medium with magnetic readout, representing a promising perspective for high-density information storage and quantum computing applications. In the case of DNA, DNA-based honeycomb films were successfully constructed through the encapsulation of DNA with a cationic surfactant ditetradecyldimethylammonium (DTDA). DNA exists in the double helical B-form in the microporous film. And, we have prepared a fluorescent microporous film through loading dye molecule rhodamine B into the DTDA/DNA complex. In both cases, we could adjust the size of holes in the microporous films by changing the correlative experimental parameters, such as the concentration of the complex, velocity of humid airflow and solvent type.In summary, we have prepared self-organized microporous films of polyoxometalate, Mn12, and DNA, respectively, via breath figures, through the surface modification of organic molecules. The proper hydrophobicity of the materials was proved to be essential for the formation of ordered honeycomb films. The structure of the microporous films could be adjusted by changing the correlative experimental parameters. Importantly, the properties of polyoxometalate, Mn12, and DNA are well maintained in the microporous films, which lay a solid foundation in the extensive applications of the microporous films.