19 nm‐Thick Grafted‐To Polymer Brushes onto Optimized Poly(Dopamine)‐Coated Surfaces

• Published in: Advanced materials interfaces 2023-06, Vol.10 (18), p.n/a
• Main Authors: Teunissen, Lucas W., Smulders, Maarten M. J., Zuilhof, Han
• Format: Article
• Language: English
• Subjects: Block copolymers; Brushes; coatings; Contact angle; copolymers; Deposition; Dopamine; Film thickness; Graft copolymers; grafting‐to; Isopropylacrylamide; Photoelectrons; poly(dopamine); Polymer coatings; Polymers; Primers (coatings); responsive; Silicon substrates; Spectroellipsometry
• ISSN: 2196-7350; 2196-7350
• DOI: 10.1002/admi.202202503

Grafting‐to polymer coatings are typically easy to apply, but the thickness of such coatings is typically limited to a few nanometers, which may hamper applications. This paper presents a grafting‐to coating approach that yields polymer brushes up to an unprecedented thickness of 19 nm. To this aim, an easy‐to‐apply poly(dopamine) (PDA) primer layer is optimized. PDA is an easy‐to‐apply, but highly complex and chemically not well understood primer layer. In this study, PDA is deposited on silicon substrates using several deposition protocols (pH 4–7 in presence of NaIO4, and from Tris solution at pH 8.5). The modified surfaces are characterized using X‐ray photoelectron spectroscopy, spectroscopic ellipsometry, static water contact angle measurements, and atomic force microscopy. Subsequently, block copolymers of poly(glycidyl methacrylate)20‐b‐poly(N‐isopropylacrylamide)n are attached onto the PDA films using a grafting‐to approach. The results indicate that the conditions of PDA deposition and the PDA film thickness strongly influence the stability and grafting efficiency of the block copolymers. PDA films deposited at pH 7 with NaIO4 are stable, and yield the most efficient grafting, with grafted polymer layers as thick as 19 nm. Polymer layers of such thickness are rarely achieved using grafting‐to procedures from solution. This work presents a new grafting‐to coating approach for polymer brushes up to a thickness of 19 nm. To this end, deposition conditions of a poly(dopamine) primer layer are optimized, onto which block copolymers of poly(glycidyl methacrylate)‐b‐poly(N‐isopropylacrylamide) are grafted. The conditions of poly(dopamine) deposition and related film thickness are found to influence the stability and grafting efficiency of the block copolymers.