Biocompatible and blood-compatible surface modification is urgently needed for stainless steel (SUS)-based human implant devices to avoid inflammation and biofouling. To this end, the use of polymeric surface modifiers, whose surface properties are specifically tailored, is a promising approach since this approach minimizes the impact on device's mechanical properties. However, adhesion between the device and surface modifier is relatively weak, since van der Waals forces are employed, leading to low device durability. To address this issue, this work functionalized poly(-caprolactone)-b-[poly(-chloride--caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine)](2) (PCL-b-(PCL-Cl-b-PMPC)(2)) with catechol groups via a nucleophilic substitution, whereby the catechol functionalization was optimized. The resultant surface modifier showed strong adhesion toward SUS surfaces, forming a smooth and uniform hydrophilic polymeric film that reduced SUS fouling (i.e., protein). Notably, no significant changes of adhesion between the SUS and thin films (thin film) were observed after immersion for 45 days in a pH 7.4 phosphate buffer solution. (c) 2017 Wiley Periodicals, Inc.