Stretchable, Transparent, Permeation Barrier Layer for Flexible Optics

Abstract Flexible, compliant permeation barrier layers are critically needed in the optics/optoelectronics industry to protect deformable, polymer‐based optical elements, such as those found in variable focus lenses. To address these needs, a transparent and deformable polymeric permeation barrier coating consisting of poly(1H,1H,6H,6H‐perfluorohexyl diacrylate) (pPFHDA) is prepared by initiated chemical vapor deposition. pPFHDA is a highly crosslinked fluoropolymer, which is deposited onto temperature‐sensitive elastomeric membranes at ambient temperature with high uniformity and conformality. This is believed to be the first demonstration of vapor deposition of the PFHDA monomer. Coatings with thicknesses nominally ranging from 200 to 750 nm are prepared and shown to be impermeable to high‐index optical fluid (polyphenyl thioether) over 2 months at 70 °C, which translates to more than 4 year lifespan at room temperature, even after being subjected to 0.26% biaxial strain. Moreover, due to its amorphous nature, the pPFHDA is transparent from wavelengths of 300–1690 nm and also thermally stable to temperatures of 300 °C. These properties should make pPFHDA coating a particularly compelling candidate for flexible optical/optoelectronic devices requiring transparent and compliant barrier layers.