Bridging Polymer Brushes and Coatings Through Ultra‐Thick Growth by Surface‐Initiated Photoiniferter Polymerization

Abstract

Bridging the gap between polymer brushes and bulk‐like coatings remains a major challenge in the development of functional surface‐grafted materials. Here, we demonstrate that surface‐initiated photoiniferter‐mediated polymerization (SI‐PIMP) enables the controlled synthesis of ultra‐high molecular weight (UHMW) polymer brushes with thicknesses in the multi‐micrometer range under mild conditions. The polymerization features characteristics of a controlled/living mechanism, including low dispersity, predictable molecular weight evolution, and successful chain extension and block copolymerization. Brush thicknesses exceeding 3 µm are achieved while retaining signatures of controlled growth, reaching a regime typically associated with bulk coatings rather than conventional thin polymer brushes. The resulting UHMW brushes display distinct physicochemical and tribological properties compared to thinner brush layers. In particular, increasing brush thickness leads to reduced friction coefficients and enhanced wear resistance under aqueous sliding conditions. This behaviour is attributed to improved fluid retention within the polymer matrix, sustained hydration‐mediated lubrication, and enhanced steric stabilization at the interface. Overall, SI‐PIMP provides an effective strategy to bridge molecular polymer brushes and bulk coatings, opening new opportunities for durable and lubricating functional interfaces.