pH Responsive and Oxidation Resistant Wet Adhesive based on Reversible Catechol–Boronate Complexation

Abstract

A smart adhesive capable of binding to a wetted surface was prepared by copolymerizing dopamine methacrylamide (DMA) and 3-acrylamido phenylboronic acid (AAPBA). pH was used to control the oxidation state and the adhesive property of the catechol side chain of DMA and to trigger the catechol–boronate complexation. FTIR spectroscopy confirmed the formation of the complex at pH 9, which was not present at pH 3. The formation of the catechol–boronate complex increased the cross-linking density of the adhesive network. Most notably, the loss modulus values of the adhesive were more than an order of magnitude higher for adhesive incubated at pH 9 when compared to those measured at pH 3. This drastic increase in the viscous dissipation property is attributed to the introduction of reversible complexation into the adhesive network. Based on the Johnson Kendall Roberts (JKR) contact mechanics test, adhesive containing both DMA and AAPBA demonstrated strong interfacial binding properties (work of adhesion (Wadh) = 2000 mJ/m2) to borosilicate glass wetted with an acidic solution (pH 3). When the pH was increased to 9, Wadh values (180 mJ/m2) decreased by more than an order of magnitude. During successive contact cycles, the adhesive demonstrated the capability to transition reversibly between its adhesive and nonadhesive states with changing pH. Adhesive containing only DMA responded slowly to repeated changes in pH and became progressively oxidized without the protection of boronic acid. Although adhesive containing only AAPBA also demonstrated strong wet adhesion (Wadh ∼ 500 mJ/m2), its adhesive properties were not pH responsive. Both DMA and AAPBA are required to fabricate a smart adhesive with tunable and reversible adhesive properties.

Wet and Functional Adhesives from One‐Step Aqueous Self‐Assembly of Natural Amino Acids and Polyoxometalates

“…[1,2] In this regard, sessile organisms,which can position themselves on awet solid surface through secreting adhesive proteins under water, [3] provide ideal models for researchers to understand the adhesion mechanism, and in turn, to create artificial adhesives.Adhesive proteins usually fold and/or selfassemble into cross-linked 3D networks to strengthen the internal cohesion forces and the elastic modulus. [1,2] In this regard, sessile organisms,which can position themselves on awet solid surface through secreting adhesive proteins under water, [3] provide ideal models for researchers to understand the adhesion mechanism, and in turn, to create artificial adhesives.Adhesive proteins usually fold and/or selfassemble into cross-linked 3D networks to strengthen the internal cohesion forces and the elastic modulus.…”

A Facile Route to Bio‐Inspired Supramolecular Oligo(Ethylene Glycol) Catecholates

“…Lastly, Scheme illustrates some possible mechanisms for the proposed interactions between the end‐groups of the PEG‐DOPAs, and with the glass and stainless steel surfaces.…”

“…Possible mechanisms for the proposed end‐group interactions between PEG‐DOPA oligomeric chains (a), based on hydrogen‐bonding between hydroxyl groups of neighboring catechol moieties (tosylate counterions omitted for clarity); Possible mechanisms for adsorption of PEG‐DOPAs on glass, based on (b) hydrogen‐bonding with surface OH groups, or (c) with oxygen atoms from the silicate network (tetrahedral SiO 2 structure simplified here for illustration purposes); Possible mechanisms for adsorption of PEG‐DOPAs on metal/metal oxide surfaces (d), based on charge transfer complex formation with metal ion …”

Cross‐Linking Building Blocks Using a “Boronate Bridge” to Build Functional Hybrid Materials

“…Narkar et al. reported a pH‐responsive and oxidation‐resistant wet adhesive system based on poly( N ‐hydroxyethyl acrylamide) with BA and dopamine moieties . pH‐responsive formation of boronate‐catechol bonds can control the strength of adhesion toward a borosilicate substrate.…”