Hydrophobically Modified Poly(acrylic acid) Coatings on Silicone Hydrogel Contact Lens

Abstract

Silicone hydrogel (Si-Hy) contact lenses offer high oxygen permeability and mechanical durability but often exhibit poor surface wettability due to the intrinsic hydrophobicity of silicone components. We investigated hydrophobically modified poly(acrylic acid) (PAA)-based amphiphilic copolymers as coating materials for Si-Hy lenses to effectively cover the chemically heterogeneous surface. A series of statistical copolymers was synthesized by copolymerizing acrylic acid with alkyl acrylates bearing linear alkyl side chains with a varying number of carbon atoms from 6 to 12. By varying molecular weight, hydrophobic content, and alkyl chain length, we examined how hydrophobic interactions influence solution behavior, interfacial properties, and coating performance. Increasing hydrophobic content enhanced anchoring to silicone domains, whereas excessive hydrophobicity promoted intermolecular association of alkyl chains. Among the copolymers studied, the poly(acrylic acid-co-octyl acrylate) copolymer exhibited the lowest contact angle and friction coefficient, indicating improved wettability and lubrication. These results demonstrate that amphiphilic coatings with optimized hydrophobic contents and alkyl chain lengths can effectively improve the interfacial properties of Si-Hy lenses.