DOI: 10.1002/adfm.200700299 Structural Evolution of Self-Assembling Nanohybrid Thin Films from Functionalized Urea Precursors** By Inna Karatchevtseva,* David J. Cassidy , Michel Wong Chi Man, David R. G. Mitchell, John V. Hanna, Carole Carcel, Catherine Bied, Joël J. E. Moreau, and John R. Bartlett 1. Introduction In the last decade there has been an increasing need for thin films driven mostly by the requirements for enhancing the properties of electronic semiconductor devices, [1] optical coat- ings, [2] and ferromagnetic applications. [3] Although such devices have traditionally been fabricated as inorganic materials, ad- vances in synthetic and characterization techniques have led to a growing interest in the development of organic-inorganic hy- brid thin films, especially where the targeted properties can be tuned by modulating the properties of the organic fragments. [4] Sol-gel processing is a versatile method for preparing nano- hybrid coatings with a wide range of compositions and nano- structures, which makes them attractive candidates for applica- tions in optics, sensing and microelectronics, in addition to protective layers on a variety of substrates. The sol-gel hydro- lytic condensation of organosilylated monomers represents one of the most facile approaches for producing hybrid organic-in- organic thin films with organic functionalities. In this context, organo-bridged di-silanes, (EtO) 3 Si-R-Si(OEt) 3 , are poten- tially useful candidates for preparing multifunctional thin films, based on their widespread use in the preparation of bulk silses- quioxanes [5,6] for a variety of applications. [7–10] In particular, we have previously reported a synthetic approach for preparing hybrid materials with controlled porosities, [11] and for solid-liq- uid phase extraction of lanthanides and actinides [12] . In addi- tion, there have been many reports of sol-gel strategies for pre- paring amorphous, bulk hybrid materials as recyclable and efficient heterogeneous catalysts for several types of organo- metallic reactions [13–15] including asymmetric reduction of pro- chiral ketones, [13] Suzuki cross-coupling reactions [14a] and Ho- veyda-Grubbs ring closure metathesis reactions. [14b] Recently, significant progress has been made toward the structuring of such bridged silsesquioxanes through the con- trolled self-assembly of the organic fragments. A broad array of shape- and size-controlled morphologies based on organo- silsesquioxanes has now been reported, with controlled organi- zation achieved on scales ranging from the molecular to tens of micrometers. [16–19] Combining molecular self-assembly with layer deposition methods such as spin-, dip- or spray-coating is of interest as a potentially new chemical patterning process, for creating multifunctional surfaces in specific patterns at the (molecular) nanoscale level. Such approaches are complemen- tary to the use of external templating agents such as surfac- tants, [20–23] which have been exploited to generate mesoporous hybrid films based on bridged silsesquioxanes through an evap- oration-induced self-assembly process. [24] This latter technique has been used to produce a variety of functional coatings, in- cluding photoactive bridged silsesquioxanyl thin films [25] and coatings consisting of polydiacetylene/silica nanocomposites with tuneable mesostructures exhibiting a reversible chromatic transition. [26] The growing interests in such structured materials with con- trolled functionalities prompted us to evaluate the possibility of extending these self-assembled nanostructures to thin films, particularly in the case of a chiral diurea compound which was reported to generate helical fibers with controlled handed- ness [16a] or hollow tubes, [16c] depending on the processing condi- tions employed. In this paper, we report the preparation of thin 3926 © 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Adv. Funct. Mater. 2007, 17, 3926–3932 – [*] Dr. I. Karatchevtseva, D. J. Cassidy, Dr. D. R. G. Mitchell, J. V. Hanna ANSTO Institute of Materials and Engineering Science PMB 1, Menai NSW 2234 (Australia) E-mail: ikm@ansto.gov.au Dr. M. Wong Chi Man, Dr. C. Carcel, Dr. C. Bied, Prof.J. J. E. Moreau ICG Montpellier (UMR 5253), ENSCM CNRS UM I UM II Laboratoire Architectures Moléculaires et Matériaux Nanostructurés Ecole Nationale Supérieure de Chimie de Montpellier 8, rue de l’école normale, 34296 Montpellier cedex 5 (France) Dr. J. R. Bartlett School of Natural Sciences University of Western Sydney Locked Bag 1797, Penrith South DC, NSW 1797 (Australia) [**] Financial supports from the “Ministère de la recherche de France” through the “ACI Nanosciences-Nanotechnologies programs” and CNRS are acknowledged. Supporting Information is available online through Wiley InterScience or from the authors. Hybrid organic-inorganic thin films exhibiting patterned structuring on the nanometer scale have been prepared through the controlled hydrolysis-condensation of enantiomerically pure chiral urea-based silyl compounds. The thin films are obtained by spin-coating of sols obtained via acid- or base-catalyzed hydrolytic condensation of these molecular precursors. A self-templat- ing process is demonstrated via atomic force and transmission electron microscopy, showing the formation of nanometer size aggregates consisting of interconnected spherulates under acidic condition and of assembled fibers under basic conditions. FULL PAPER