Figure 4: Metal–ion-responsive adhesion of βCD–bpy gel to tBu gels.
From: A metal–ion-responsive adhesive material via switching of molecular recognition properties
(a–c) Photographs of metal–ion-responsive adhesion between two pieces of βCD–bpy gel and tBu gel (20). Each piece of gel was coloured with dyes for clarity (βCD–bpy gel; red. tBu gel (20); green). Scale bars, 5 mm. (a) A piece of βCD–bpy gel immersed in CuCl2 aqueous solution adhered to that of tBu gel (20). Removal of Cu2+ from βCD–bpy gel by immersion in an aqueous solution of EDTA·4Na switched off its adhesion ability. (b) A piece of βCD–bpy gel did not adhere to that of tBu gel (20) without immersing in metal solutions. (c) A piece of βCD–bpy gel immersed in FeCl2 aqueous solution did not adhere to that of tBu gel (20). (d–f) Tensile adhesive strength between two pieces of βCD–bpy gel and tBu gel (x) immersed in metal salt solutions (error bars, s.e.m. (n=3)). (d) Immersion in various metal salt solutions (tBu gel (10), [MCl2]=10 mM (M2+=metal ion, 3 eq [/bpy])). (e) Immersion in CuCl2 aqueous solutions with different concentrations (tBu gel (10), [CuCl2]=x mM (Cu2+, 2x eq [/bpy])), and treatment of gels preimmersed in a 10 mM solution of CuCl2 with a solution of EDTA·4Na as a metal chelator. (f) tBu gels (x) with different mol% contents of tBu groups ([CuCl2]=10 mM (3 eq [/bpy])) and treatment of gels with an aqueous solution of tBuOH as an inhibitor of the host–guest complex.
