Large-Scale Formation of Fluorosurfactant-Doped Transparent Nanocomposite Films Showing Durable Anti-Fogging, Oil-Repellent, and Self-Healing Properties
By Tomoya Sato, Gary J. Dunderdale, and Atsushi Hozumi
June 16, 2020
Transparent nanocomposite films with multiple functionalities, such as durable anti-fogging, dynamic oleophobic, self-healing properties, were successfully prepared by a simple spin- or spray-coating method using aqueous solutions of polyvinylpyrrolidone (PVP) and aminopropyl-functionalized nano-clay (AMP-clay) platelets. In this study, anionic/waterborne perfluorooctanesulfonic acid potassium salt (PFOS) was pre-mixed with the aqueous PVP solution to achieve a homogeneous dispersion of PFOS. Due to the addition of PFOS, the resulting nanocomposite film surfaces displayed statically hydrophobic (static water contact angle over 90°) and dynamically oleophobic (5 L oil droplets could slide off of the surface at low sliding/substrate tilt angles of less than 10°) behaviors. In spite of our nanocomposite film surface exhibiting a statically hydrophobic nature, the anti-fogging properties remained unchanged even after being left under high humidity conditions (over 80 % relative humidity) for 3 days. Thanks to both exceptional water-absorbing properties of PVP/AMP-clay matrices and good mobility of PFOS driven by moisture, our oil-repellent nanocomposite films could be repeatedly self-healed even after both severe physical (cutting, scratching, or falling sand abrasion) and chemical (vacuum UV oxidation) damages. Large-scale fabrication of this multi-functional nanocomposite film (30 cm × 30 cm) could be also successfully demonstrated by a spray-coating method based on in-situ gel formation.