Clear Anti-Smudge Coatings of Diblock Copolymers

Abstract

Two poly[3-(triisopropyloxysilyl)propyl methacrylate]-block-poly[2-(perfluorooctyl)ethyl methacrylate] (PIPSMA-b-PFOEMA or P1-1/P1-2) samples and one poly(perfluoropropylene oxide)-block-poly-[3-triisopropyloxysilyl)propyl methacrylate] (PFPO-b-PIPSMA, or P2) sample were synthesized, characterized, and used to coat glass plates. The coatings were formed by evaporating a dilute copolymer solution containing an HCl catalyst to facilitate the sol-gel chemistry of the PIPSMA blocks. To minimize polymer consumption, we targeted diblock copolymer unimolecular (brush) layers that consisted of a sol-gelled PIPSMA sub-layer that was anchored onto the glass plates, and a fluorinated surface layer that provided the desired water and oil repellency. A systematic study was performed examining the effect of varying the catalyst amount, the polymer amount, and the block copolymer composition on the structure, morphology, and water- and oil- repellency of the coatings. The amphiphobicity of the coatings improved initially with the amount of grafted polymer, but plateaued once a saturated brush layer was formed. Furthermore, the static contact angles (SCAs) increased as the relative length between the PFOEMA and PIPSMA blocks increased. All of the coatings were optically clear and repelled ink from a permanent Sharpie® marker. The markings that were left behind were the faintest on the P2 coatings as the ink would instantaneously shrink into patches. In addition, the P2 coatings exhibited far better wear-resistance than the P1-1/P1-2 coatings. The anti-smudge properties of the coatings should facilitate their use on touch screens of hand-held electronic devices such as iPads® and iPhones®.