(589h) Cooperative Hydrogen Bonding – Towards Robust Underwater Adhesion

Epoxy polymeric adhesives have found a variety of uses due to their exceptional adhesive strength, toughness, and applicability to many types of substrates.¹ However, they suffer from a great reduction in adhesion when applied in wet environments, severely limiting their applications.² Previous work has compared the effect of various surface treatments on the adhesive strength of DGEBA epoxy adhesives to aluminum panels in dry and hot/wet conditions. Surfaces treated with the tris buffer (tris(hydroxymethyl)aminomethane) outperformed untreated and silane/DOPA treated surfaces in both dry and wet lap shear tests. Cooperative hydrogen bonding was hypothesized as the possible mechanism for enhanced adhesion.³

DGEBA oligomers incorporating tris were synthesized to determine the mechanism behind the increase in adhesive performance. We measured the interactions between 100 nm oligomer films with mica or Aluminum in air and under water. By varying the rate of crack propagation during detachment the lifetime of interfacial bonds can be determined, allowing us to characterize the kinetics of adhesive bonds in situ.⁴ We then relate rate-dependent adhesion to a model for cooperative hydrogen bonding suggesting that through cooperation, polymer hydrogen bonds can compete with interfacial water to maintain adhesive interactions under water.

(1) Schmidt, R. G.; Bell, J. P. Epoxy Adhesion to Metals. In Epoxy Resins and Composites II; Dušek, K., Ed.; Springer-Verlag: Berlin/Heidelberg, 1986; Vol. 75, pp 33–71. https://doi.org/10.1007/BFb0017914.

(2) Kerr, C.; Macdonald, N. C.; Orman, S. Effect of Certain Hostile Environments on Adhesive Joints. Journal of Applied Chemistry 2007, 17 (3), 62–65. https://doi.org/10.1002/jctb.5010170301.

(3) Tran, N. T.; Flanagan, D. P.; Orlicki, J. A.; Lenhart, J. L.; Proctor, K. L.; Knorr, D. B. Polydopamine and Polydopamine–Silane Hybrid Surface Treatments in Structural Adhesive Applications. Langmuir 2018, 34 (4), 1274–1286. https://doi.org/10.1021/acs.langmuir.7b03178.

(4) Chaudhury, M. K. Rate-Dependent Fracture at Adhesive Interface. J. Phys. Chem. B 1999, 103 (31), 6562–6566. https://doi.org/10.1021/jp9906482.