Self-Assembled Monolayers Generated from Unsymmetrical Partially Fluorinated Spiroalkanedithiols.

Area of Science:

• Surface Chemistry
• Materials Science
• Nanotechnology

Background:

• Self-assembled monolayers (SAMs) are crucial for modifying surface properties.
• Partially fluorinated adsorbates offer tunable surface characteristics.
• Bidentate adsorbates present unique structural possibilities for monolayer formation.

Purpose of the Study:

• To synthesize and characterize novel unsymmetrical partially fluorinated spiroalkanedithiol adsorbates for SAM formation.
• To investigate the influence of deposition conditions on SAM structure and properties.
• To compare the performance of these new SAMs against established semifluorinated and non-fluorinated analogues.

Main Methods:

• Synthesis of a novel spiroalkanedithiol adsorbate [CH3(CH2)7][CF3(CF2)7(CH2)8]C[CH2SH]2 (SADT).
• Formation of SAMs on gold substrates using various solvents and temperatures.
• Characterization techniques including contact-angle measurements and analysis of film thickness and conformational order.

Main Results:

• SAMs formed in DMF at room temperature exhibited optimal sulfur headgroup binding and higher conformational order.
• SADT SAMs showed reduced film thickness and enhanced wettability compared to F8H10SH SAMs.
• Despite looser packing of fluorinated segments, SADT SAMs possessed denser underlying hydrocarbon chains due to their double-chained structure.
• Conformational order decreased in the series: n-octadecanethiol > F8H10SH > SADT.

Conclusions:

• The novel bidentate adsorbate enables the formation of SAMs with distinct fluorinated interfaces.
• Optimized deposition in DMF yields well-ordered SAMs with low surface roughness.
• These findings offer new avenues for designing surfaces with tailored properties using advanced adsorbates.