We have demonstrated a universal approach to growing polymer brushes from various substrates. Urushiol was mixed with initiator-containing catechol, and it was spin-coated or cast on various substrates. Because urushiol is strongly adhered to various substrates, the thin film can serve as a general scaffold for grafting polymer brushes from various substrates. Note that the film was formed even onto the surface of polyolefins and thermosetting resins that are known as chemically inert materials to functionalize the surface. Moreover, the initiator-immobilized scaffold showed mechanical robustness and chemical inertness because of the flexible long unsaturated hydrocarbon side chain of urushiol. After the grafting of polyelectrolyte PMTAC polymer brushes, the material obtained exhibited hydrophilicity, typical of PMTAC. The concept shown here could provide a general approach for grafting practical polymer brushes from various substrates.

We have demonstrated the growth of polymer brushes from a surface-textured thin urushiol film. Thermal imprinting was done on an initiator-immobilized thin urushiol film, and surfaceinitiated atom-transfer radical polymerization (ATRP) of [2-(methacryloyloxy)ethyl]trimethylammonium chloride (MTAC) was conducted from it. The obtained surface showed superhydrophilicity because of the nature of polyelectrolyte polymer brushes on the textured surface. Since thin urushiol film can form on a variety of substrates, the concept shown here could be a universal approach for surface modifications of substrates."Urushi" (oriental lacquer) is a traditional natural resin that is often applied as a coating for wood or paper substrates. 1The main component in urushi, called urushiol, is a catechol derivative with a long unsaturated hydrocarbon side chain (Figure 1). 24 Catechol derivatives are also found in the adhesive protein in mussels that is currently attracting attention as biomimetic natural adhesives. 57 Since catechol derivatives can adhere on various substrates, these derivatives are useful as a universal surface modification method of various artificial materials. The advantage of urushiol over other catechol derivatives arises from the unique side chain. Thermal Diels Alder reactions and thermal addition reactions of the unsaturated hydrocarbon side chains accelerate the curing, 8,9 and thermal curing completes within minutes; in contrast, conventional oxidative polymerization of catechol derivatives requires over 12 h to cure. Moreover, the flexibility of the side chain imparts robustness to the cured material. 1012 Utilizing these characteristics, we demonstrated that thin urushiol films can serve as a universal, tough scaffold for grafting polymer brushes.11 Initiator-containing thin urushiol films were formed on various substrates, including polyolefins and thermosetting resins that are known as chemically inert materials to functionalize the surface. Then, polyelectrolyte polymer brushes were grafted from it. Since polymer brushes are candidate for surface modification, growing polymer brushes from various substrates widens the variety of applications.Surface properties are strongly influenced by its surface topography as well as chemical composition. 13 For example, water repellence of lotus leaves resulting in self-cleaning properties arises from micron-sized papillae coated with epicuticular waxes.14 By mimicking the design in nature, artificial functional surfaces were fabricated by the combination of the surface texturing and the following polymer brush growth. Although various techniques such as UV nanoimprintings, 15,16 photopatternings, 17 and patterned self-assembled monolayer (SAM) modifications 18,19 were used for surface texturing, they are subject to certain restrictions in various substrates. For example, SAM modification is generally useless for plastics. Moreover, several substrates such as polyolefins and thermosetting resins are difficult to apply to these techniques because of their chemic...