Roll-to-Roll Vapor Deposition of Hydrophobic and Transparent Nano-Adhesive Polymeric Thin Films on Rigid and Flexible Substrates

This paper demonstrates the adhesive and hydrophobic modifications of glass, poly­(ethylene terephthalate), and bamboo fabric surfaces using the initiated chemical vapor deposition (iCVD) process. iCVD of functional thin films is an all-dry and low-temperature alternative to the conventional wet coating processes. The as-deposited film is a terpolymer in which ethylhexyl acrylate and acrylic acid units comprised the pressure-sensitive adhesive (PSA) part, while perfluorodecyl acrylate (PFDA) acted as the hydrophobic part due to its low surface energy fluorinated side groups. The PFDA composition in the iCVD terpolymer can be systematically varied by adjusting the initial gas feed fractions of monomers, as verified from FTIR and XPS analyses. The usage of the initiator tertbutyl peroxide during the depositions resulted in high deposition rates up to 80 nm/min at a filament temperature of 230 °C. The as-deposited films possessed high optical transparency with high shear and peel strength values. Depending on the chemical composition, the peel strength values were up to 0.5 N/25 mm on flexible PET substrates. After the coating, the highly porous bamboo surface not only became sticky due to the existence of the thin PSA layer on top but also the became near-superhydrophobic. The application of iCVD coating parameters to deposit hydrophobic PSA on moving large-area substrates under roll-to-roll deposition mode resulted in highly uniform coatings, which shows the potential of iCVD to be operated in industrial scales to functionalize the industrially important flexible substrates.