Hydrophilic polymers show unique characteristics at various interfaces. High-density hydrophilic polymer brushes nano-coatings were prepared on Si-wafer and various substrates by surface-initiated controlled radical polymerization. Chain conformation at liquid/solid liquid/solid interface was characterized by neutron reflectivity. Applications of polymer brushes as structural nano-coatings such as super hydrophilicity, antifouling behavior, low friction behavior, and intelligent adhesion are presented.