Polymer Brush Growth by Surface‐Initiated Ring‐Opening Polymerization from a Cross‐Linked Polymer Thin Film

Abstract

Modification of a surface with polymer brushes has emerged as an effective approach to tune the properties of a substrate. Brushes grown from an inimer‐containing cross‐linkable polymer coating provide significant advantages compared to other “grafting‐from” methods, such as improved stability, increased grafting density, and the potential to control the grafting density. So far, the inimer coating method has only been applied for surface‐initiated controlled radical polymerizations. In this work, an approach is presented for the fabrication of a stable cross‐linked ultra‐thin polymer coating containing hydroxyl groups which serve as initiating sites for surface‐initiated ring‐opening polymerization (SI‐ROP). The polymers used for the fabrication of the coatings consist of 2‐((tetrahydro‐2H‐pyran‐2‐yl)oxy)ethyl methacrylate (THPEMA), a small fraction of a cross‐linkable unit, and a diluent styrene. Three coatings with varying THPEMA and styrene content are fabricated, and poly(dimethyl siloxane) (PDMS) and poly(caprolactone) (PCL) brushes are grown by SI‐ROP of hexamethylcyclotrisiloxane (D3), and ε‐caprolactone respectively. The brushes are characterized by atomic force microscopy (AFM), X‐ray photoelectron spectroscopy (XPS), static contact angle measurements, ellipsometry and size exclusion chromatography (SEC). The results demonstrate a well‐controlled ROP of D3 and ability to control grafting density by tuning the THPEMA content of the coatings.