Doping in poly(o-ethoxyaniline) nanostructured films studied with atomic force spectroscopy (AFS)

Area of Science:

• Materials Science
• Surface Science
• Polymer Chemistry

Background:

• Interfacial intermolecular interactions are crucial for sensing and biosensing applications.
• Probing interfacial phenomena is challenging, with atomic force spectroscopy (AFS) being a key technique.
• Understanding these interactions aids in developing advanced materials and devices.

Purpose of the Study:

• To investigate the adhesion forces of poly(o-ethoxyaniline) (POEA) films doped with various acids using AFS.
• To correlate the doping-induced changes in POEA morphology and interfacial interactions.
• To explore the influence of doping on the physical properties of semiconducting polymers.

Main Methods:

• Atomic Force Spectroscopy (AFS) to measure adhesion forces.
• Small-Angle X-ray Scattering (SAXS) to analyze polymer conformation in solution.
• AFM measurements in both air and a liquid cell to study pH-dependent behavior.

Main Results:

• Adhesion forces were lower for POEA doped with inorganic acids (HCl, H2SO4) than organic acids due to ethoxy group screening.
• POEA morphology and conformation varied significantly with the doping acid and solvent (DMAc vs. water).
• AFS in a liquid cell showed pH-dependent forces: van der Waals at pH≥5 (dedoped) and double-layer repulsion at pH≤3 (doped).

Conclusions:

• AFS can effectively correlate molecular-level interactions with the doping and morphology of semiconducting polymers.
• The choice of doping acid critically influences the interfacial properties and conformation of POEA.
• This study provides insights into the behavior of semiconducting polymers at interfaces, relevant for sensor development.