Adhesion Behavior of Catechol-Incorporated Silicone Elastomer on Metal Surface

Herein, we designed a catechol-based compound, 4-allyl pyrocatechol (APC), which contains catechol and alkene groups capable of interacting with various metal oxide substrates and being chemically incorporated into a polydimethylsiloxane (PDMS) matrix, respectively. Due to the specific interactions between the catechol and metal oxide surface, this compound incorporated in PDMS can act as a surface "active" additive that effectively enriches the adhesion interface, leading to the improvement of adhesion between PDMS and the substrate. The adhesion property was evaluated by measuring the lap shear strength on various metal substrates, such as aluminum (Al), stainless steel (SUS), and copper (Cu) (each with an oxide skin layer), and compared with that of the commercial additive, 3-glycidoxypropyltrimethoxysilane (GPTMS). Remarkably, APC-incorporated PDMS adhered to metal oxide substrates exhibited the maximum shear strength at a lower loading than GPTMS, suggesting that APC enhances the adhesion of PDMS onto metal oxide surfaces more significantly than GPTMS. For example, it was observed that even 0.3 wt % APC improves the strength on SUS substrates by 1200%, demonstrating that APC is a very effective additive. This improved adhesion behavior is considered to be the consequence of surface segregation of APC groups, as corroborated by surface analysis and molecular dynamics simulations.