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. 2021 Oct 4;60(44):23687–23694. doi: 10.1002/anie.202100064

Figure 2.

Figure 2

Adhesion investigation of the SUP coacervate glues. A) Lap shear strength for the SUP‐NDP adhesives on three different substrates (Steel, PE, and PVC). K72‐NDP and K108‐NDP were chosen as representative examples and cyanoacrylate was used as a control. P‐values were calculated using the student's t‐test. ns, not significant difference; *p=0.013 <0.05, *** p=0.0003 and 0.0006 <0.001 (in the group of steel), **p=0.0017 and 0.0023 <0.01 (in the group of PE), * p=0.049 <0.05, ** p=0.0077 <0.01 (in the group of PVC). B) The effect of different metal ions (Fe3+, Tb3+) on the bonding strength of SUP‐NDP adhesives on steel (K72‐NDP and K108‐NDP). *p=0.012 <0.05, ***p=0.00039 <0.001 (in the group of K72), * p=0.031 <0.05, ** p=0.0019 <0.01 (in the group of K108). C) Lap shear strength for SUP‐NAT glues (K72‐NAT and K108‐NAT) on three different substrates (Steel, PE, and PVC). *p=0.016 <0.05 (in the group of steel), **p=0.002 <0.01 (in the group of PE), *p=0.0015 <0.05, ** p=0.009 <0.01, **** p=0.00008 <0.0001 (in the group of PVC). D) Lap shear strength for SUP‐PDD glues (E36‐PDD, E72‐PDD, and E144‐PDD) on three different substrates (Steel, PE, and PVC. *p=0.018 <0.05, ** p=0.0066 <0.01, *** p=0.00041 and 0.00061 <0.001 (in the group of steel), * p=0.022 <0.05, **p=0.0032, 0.0014, and 0.0042 <0.01 (in the group of PE), * p=0.013 <0.05, ** p=0.0049 <0.01, ***p=0.00028 <0.001 (in the group of PVC). E–H) Adhesion energy of SUP adhesives under different conditions. I–J) Lap shear strength and adhesion energy of SUP‐BnNDP on steel before/after Fe3+ ion treatment. K) Schematic for the adhesion mechanism of SUP‐surfactant adhesives. Besides electrostatic interactions, van der Waals forces, hydrophobic interactions, and hydrogen bonds both inside the complex and on the interface of samples and substrates, cation–π, and metal coordination bonding between catechol units of surfactant and metal ions are important to enhance the adhesion effect of SUP‐surfactant complexes. The brown cylinder and cyan fiber represent surfactant and SUP, respectively. The deep blue sphere represents metal ions, including Fe3+ and Tb3+.