X-ray Analysis of Polymer-inorganic Hybrid Nanostructures

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Ulrich Wiesner
Materials Science and Engineering, Cornell University

Abstract:
In the second half of the 90’s concepts developed in the field of polymer science were successfully transferred to structure amorphous aluminosilicates on the tens of nanometer scale¹. In these studies x-ray analysis was pivotal for structure determination. By using thermodynamic principles established for block copolymers, inorganic sol-nanoparticles were structure directed into well-defined morphologies. Burning out of the organic compounds resulted in nanoporous materials with ordered and uniform pores and hexagonal as well as bicontinuous cubic pore structures. In 2004 similar concepts were employed successfully to generate the first ordered nanoporous non-oxide type ceramics stable up to 1500°C from block copolymer assembly². Similar approaches can be applied to crystalline oxides. A combination of assemblies by soft and hard (CASH) chemistries, was used to directly access thermally stable and highly crystalline nanoporous transition metal oxides with uniform pores³. These studies have demonstrated relatively facile “one-pot” type synthesis approaches to nanostructured and nanoporous materials, a requirement that should facilitate translation of research results into industrial settings. More recently, for silica-type sols the existence of a critical sol nanoparticle size was revealed relative to the size of the block copolymer required to obtain the desired structure control⁴. These results suggested that besides enthalpic contributions, entropy has to be carefully considered when mixing inorganic nanoparticles into block copolymers. The work further suggested that the same structure control should be obtained independent of the nature of the core of the nanoparticles, as long as corona chemistry and particle size are properly taken into account. For example, these results together with the development of particular charged ligand structures and use of the CASH method enabled synthesis of the first nanoporous Pt metal structures from block copolymer assembly in the bulk (see Figure 1)⁵. The present talk will describe, and give a perspective of, these approaches for future materials development and will highlight the role that x-ray analysis has played in the process. Emphasis will be on energy generation and storage as well as nanophotonics/plasmonics applications.

References

[1] M. Templin, A. Franck, A. Du Chesne, H. Leist, Y. Zhang, R. Ulrich, V. Schädler, and U. Wiesner; “Organically Modified Aluminosilicate Mesostructures from Block Copolymer Phases”, Science 278, 1795-1798 (1997).

[2] M. Kamperman, C. B. W. Garcia, P. Du, H. Ow, and U. Wiesner; “Ordered Mesoporous Ceramics Stable up to 1500°C from Diblock Copolymers”, J. Am. Chem. Soc. 126, 14708- 14709 (2004).

[3] J. Lee, M. C. Orilall, S. C. Warren, M. Kamperman, F. J. DiSalvo, and U. Wiesner; “Direct Access to Thermally Stable and Highly Crystalline Mesoporous Transition Metal Oxides with Uniform Pores”, Nature Mater. 7, 222-228 (2008).

[4] S. C. Warren, F. J. DiSalvo, and U. Wiesner; “Nanoparticle-tuned Assembly and Disassembly of Mesostructured Silica”, Nature Mater. 6, 156-161 (2007).

[5] S. C. Warren, L. C. Messina, L. S. Slaughter, M. Kamperman, Q. Zhou, S. M. Gruner, F. J. DiSalvo, and U. Wiesner; “Ordered Mesoporous Materials from Metal Nanoparticle-block Copolymer Self-assembly”, Science 320, 1748-1752 (2008).