Discrete Brush Polymers Enhance ¹⁹F MRI Performance through Architectural Precision

The development of metal-free magnetic resonance imaging (MRI) agents demands precise control over molecular architecture to achieve optimal performance. Current fluorine-based contrast agents rely on maximizing fluorine content (>20 wt %) for sensitivity, requiring extensive solubilizing groups that lead to signal-diminishing aggregation. Here we show that discrete brush polymers (Đ = 1.0) with precise backbone lengths and a single terminal fluorine group achieve superior imaging performance through architectural control rather than high fluorine content. This design prevents both intra- and intermolecular fluorine aggregation while maintaining high aqueous solubility, enabling sharper signals and higher sensitivity than conventional systems despite containing less than 7 wt % fluorine. Systematic investigation reveals how backbone length controls fluorine mobility and signal generation, establishing clear structure-property relationships previously obscured by molecular heterogeneity. This work demonstrates how precise architectural control can enhance functional performance beyond traditional approaches, providing new strategies for designing imaging materials.