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The synthesis and use of polar and polarizable, amphiphilic molecules for polarization driven self-assembly
Scope and goals of research project:
Although it is now well recognized that self-assembly is going to be an important paradigm for nano-scale construction, there are few general assembly strategies. Focusing in particular on self-assembly on surfaces, it is fair to say that demonstrations in this area are dominated by the use of thiol-gold interactions. A new, monolayer-based self-assembly strategy could have immediate applications in all of the areas where the thiol/gold paradigm has been exploited. This includes biosurfaces, molecular electronics, and sensors. Our goal is to show that electrostatic interactions between a polarized ferroelectric domain and dipolar, amphiphilic molecules can be a new way to drive self-assembly that is amenable to patterning.
The first task at hand is to establish the molecular features required to self-assemble on a polarized ferroelectric domain. An amphiphilic merocyanine structure was chosen for several reasons. First of all, the merocyanine has a large, permanent molecular dipole (> 10 D) suggesting a large electrostatic interaction with (or, conversely, repulsion from) the patterned substrate. Second, the merocyanine group is an excellent spectroscopic species. Third, it is easy to vary the length of the tail group synthetically. Moreover, several choices of head group based on the merocyanine dye concept are also available.
The next task is to assemble these molecules on a polarized, patterned ferroelectric substrates with well controlled surfaces. It is anticipated that only those regions in which the ferroelectric domain is polarized opposite to the charge-transfer axis in the molecules will be covered with these molecules – ideally a close-packed monolayer of these molecules will be electrostatically adsorbed onto the surface.
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| Figure 1: |
Amphiphilic merocyanine structure for self-assembly.
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| Figure 2: |
A schematic approach for self-assembly using a patterned ferroelectric substrate as a director.
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