Exploiting the Base-Triggered Thiol/Vinyl Ether Addition to Prepare Well-Defined Microphase Separated Thermo-Switchable Adhesives

Abstract

Switchable adhesives are materials of utmost importance due to their capability of having their adhesion/cohesion properties reversibly triggered upon stimuli, allowing on-demand surface attaching/detaching. Still, several challenges mainly associated with complex uncontrolled chemical processes hinders their production. In this study, it is found that unexpectedly vinyl ethers are able to react with thiols in the presence of a catalytic concentration of base, which allows the preparation of well-defined phase-separated switchable adhesives. Indeed, these findings show that base-catalyzed thiol-acrylate and thiol-vinyl ether are highly orthogonal, making the acrylate reaction faster. This is explored to react in the first stage thiols with acrylates in the presence of vinyl ethers to end-cap all the oligomers with stable vinyl ethers and suppress undesirable disulfide formation. In a second stage the UV-triggered thiol-ene “click reaction” is carried out, forming the network. It is shown that the network prepared by this approach presents superior adhesion due to greater backbone length, a controlled crosslinking motif, and better-defined microphase separation. Additionally, the adhesives made by this strategy are thermo-switchable due to the temperature-triggered base-catalyzed thioether dynamic covalent character at 200 °C. Despite providing superior adhesive properties, the proposed technology endows scalable, thermo-switchable, and O2-resistant adhesives with huge industrialization potential.