Surface modification by functional coatings has become very attractive to develop and produce platforms with improved chemical and physical properties for various applications. The preparation of functional surface coatings in a well-controlled fashion plays an essential role in tuning the intrinsic properties of a substrate. This Thesis explored polymer brushes, which are considered as three-dimensional surface coatings, prepared via surface-initiated controlled radical polymerization techniques to engineer the properties of functional interfaces to match the requirements of specific applications and thus to prepare model interfaces for developing functional surface coatings.