Hyperbranched polymers are very different from linear polymers in terms of physicochemical properties. Meanwhile, the modification of adhesive polymers by the introduction of hyperbranched polymers 39–41 has recently become a new research hotspot due to the excellent properties of hyperbranched polymers. Interestingly their reaction conditions are similar, which leads us to speculate that the polymers produced by the Michael addition reaction and the Schiff base reaction can be obtained in a single step. 38 enabled the rapid adhesion of hydrogels and organogels at the interface of macroscopic gel sheets to form macroscopic organic hydrogel mixtures by Schiff base bonding. Schiff bases are formed by the condensation of amines and active carbonyl groups, which are a class of aldehydes and ketones containing carbonyl groups that undergo nucleophilic addition to amines, and have a wide range of applications in the field of adhesives. 37 form cohesion by self-aggregation of hydrophobic interactions and replace water molecules on the adhering surfaces in the aqueous environment thus achieving wet adhesion. For example, the hyperbranched polymers with hydrophobic main chains and hydrophilic side chains prepared by Liu et al. Michael addition is a conjugate addition reaction through an electrophilic electron acceptor with a nucleophilic electron donor and is one of the more established classes of common methods for growing carbon chains.
The preparation of multifunctional adhesives by Michael addition reaction 27–31 and Schiff base reaction 32–36 synthesis becomes an attractive solution. 26 Obviously, the choice of reaction substrate and the type of reaction chosen are important guidelines for the preparation of multifunctional adhesives.
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24,25 How to prepare multi-functional adhesives by a more simplified route is of greater importance for the research development of adhesive polymers. However, this not only requires a more complex structure of the polymer but also means that the conditions and steps required for synthesis become more cumbersome. 1–5 Numerous researchers have developed and prepared adhesives with underwater adhesion, 6–11 multiple substrate adhesion, 12–16 stretchability, 17,18 self-healing, 19 biosustainability, 20–22 moldability, 23 etc.
Introduction Modern functional adhesives often face more complex application environments, which means that adhesives need increasingly complex properties and often require multiple functions. The feasibility of the synthesis idea of simultaneous Michael addition reaction and Schiff base reaction was demonstrated, as well as the excellent performance and great application potential of FPA–PA adhesives to be recyclable on multi-substrates. The resulting FPA–PA adhesives produce tough bonding on multi-substrates such as steel, aluminum, glass, PVC, PTFE, birch and moso bamboo, which exhibited by lap shear strength of 2.4 MPa, 1.7 MPa, 1.4 MPa, 1.3 MPa, 0.4 MPa, 1.6 MPa, and 1.8 MPa, respectively. This allows us to prepare adhesives with hyperbranched crosslinking networks and recycling properties, and we have verified that FPA–PA adhesives do not exhibit significant fatigue after multiple recycling through the gluing-destruction-gluing process. This enables the branched polymeric adhesive system to have a large number of Schiff base bonds within it, an important property of Schiff base bonds is that they are dynamically reversible. Branched polyamines provide a large number of amino groups as reaction sites that can react with both carbon–carbon double bonds and aldehyde groups. In this work, we constructed a dynamic reversible adhesive based on branched polyamine (PA) and p-formylphenyl acrylate (FPA) by simultaneously performing Michael addition reaction and Schiff base reaction. It is of practical interest to obtain polymers with complex material properties in a simplified synthetic manner for a broader range of practical applications.
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