Sub-SEM polymer deposition on Teflon AF after sliding anionic polyelectrolyte drops

Determine whether adsorption or deposition of the anionic acrylamide–acrylic acid copolymer occurs at length scales below the resolution of scanning electron microscopy on Teflon AF surfaces after drop sliding, and, if present, characterize the morphology and spatial distribution of such sub-SEM deposits.

Background

The study investigates the receding contact line instability of viscoelastic drops on hydrophobic surfaces and reports polymer deposition patterns for cationic and non-ionic polyacrylamide-based solutions using SEM. In contrast, for drops containing the anionic acrylamide–acrylic acid copolymer, SEM imaging did not reveal deposition except near occasional dust particles.

Because SEM cannot resolve individual polymer chains on Teflon AF, the authors explicitly note that sub-SEM-scale deposition cannot be ruled out. Clarifying whether nanoscale deposits form in the anionic case is important for understanding how polymer–surface interactions and electrostatics influence contact line dynamics and friction without producing detectable micron-scale residues.