Kristian B Buhl, Asger H Agergaard, Rasmus K Møller, Mikkel Kongsfelt, Simon Heide-Jørgensen, Michal K Budzik, Mogens Hinge, Steen U Pedersen, Kim Daasbjerg

https://doi.org/10.1021/acsapm.0c00306

Creating interchain cross-links can improve the stability and robustness of polymer brushes. Unfortunately, the synthetic strategies required for this are often tedious and time-consuming, making their scale-up difficult, if not impossible. Herein, we utilize polysulfides to cross-link poly(glycidyl methacrylate) (PGMA) brushes grafted from stainless steel in a fast and simple step, converting the PGMA brush to a strong nanoscale adhesive layer for bonding stainless steel and ethylene–propylene–diene M-class rubber (EPDM). The polymer brush is cross-linked in aqueous solution, and the polysulfides are made from inexpensive and widely available reagents. The cross-linking introduces 10.9% sulfur in the film according to X-ray photoelectron spectroscopy, and Raman spectroscopy showed bands ascribed to S_n (n ≥ 2) species. The polysulfide cross-links may be cleaved using dithiothreitol, resulting in an uncross-linked, thiol-functionalized polymer-brush coating. When used as an adhesive layer for bonding steel and EPDM rubber, the cross-linked polymer film displays higher fracture toughness (comparable to a commercial bonding agent) than the uncross-linked film and gives cohesive failure rather than the adhesive failure seen in the latter case. We anticipate that the industrial scale-up of the procedure using, e.g., dip coating, is straightforward considering that it uses inexpensive chemicals, is oxygen tolerant, takes place in aqueous solution, and can be accomplished within half a minute.