Adhesion using the covalent bond formation reaction at the soft material interface

Abstract

Interfacial reactions are one of the most effective ways to add new functions to materials. We reported the direct adhesion of hydrogels through host-guest interactions. The selectivity of the host-guest interaction between cyclodextrins (CDs) and hydrophobic guest molecules were employed for gel adhesion on the macro scale. Many covalent bond formation reactions have been developed and applied to synthesize complex molecules or polymers. We applied these reactions to adhesion between materials, choosing the Suzuki-Miyaura cross-coupling reaction. The hydrogels with phenylboronic acid (PB-gel) and with iodophenyl groups (I-gel) were prepared by radical polymerization. The gels adhered to each other under Suzuki-Miyaura coupling reaction conditions. The adhesion strength, evaluated by creep of mater, increased with the content of functional groups. Adhesion between gels and glass substrates is demonstrated also using the Suzuki-Miyaura cross coupling reaction. The adhesion of gels to glass substrates was shown also by using the Cu catalyzed azide alkyne cycloaddition (CuAAC) reaction and the Sonogashira cross-coupling reaction as other covalent bond forming reaction.