In this work we prepare Langmuir-Blodgett monolayers with a trifunctional amphiphilic anthraphane monomer. Upon spreading at the air/water interface, the monomers self-assemble into 1 nm-thin monolayer islands, which are highly fluorescent and can be visualized by the naked eye upon excitation. In situ fluorescence spectroscopy indicates that in the monolayers, all the anthracene units of the monomers are stacked face-to-face forming excimer pairs, whereas at the edges of the monolayers, free anthracenes are present acting as edge groups. Irradiation of the monolayer triggers [4 + 4]-cycloadditions among the excimer pairs, effectively resulting in a two-dimensional (2D) polymerization. The polymerization reaction also completely quenches the fluorescence, allowing to draw patterns on the monomer monolayers. More interestingly, after transferring the monomer monolayer on a solid substrate, by employing masks or the laser of a confocal scanning microscope, it is possible to arbitrarily select the parts of the monolayer that one wants to polymerize. The unpolymerized regions can then be washed away from the substrate, leaving 2D macromolecular monolayer objects of the desired shape. This photolithographic process employs 2D polymerizations and affords 1 nm-thin coatings.
Bibliographical noteFunding Information:
The authors would like to thank Prof. J. Vermant (ETH Zurich) for providing access to light microscope and Prof. A. Studart for access to SEM. Many thanks go to Prof. N. Spencer (ETH Zurich) for providing access to AFM and to Dr. W. Dai for helping with the preparation of the gold substrates for XPS and silicon oxide substrates for AFM measurements. The help of Dr. Gabriele Fenini (Zurich University Hospital) with the photos of the fluorescent Langmuir monolayers is greatly appreciated. The authors acknowledge support of the Scientific Center for Optical and Electron Microscopy ScopeM of the Swiss Federal Institute of Technology ETHZ. ZIH Dresden is thanked for computational resources.
© 2018 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Physics and Astronomy(all)