Enhancement of the adhesion of polysiloxane-based adhesives through catechol functionalization

Abstract

In this study, polysiloxane-based adhesives were prepared by introducing a catechol component into the side chains of copolymers comprising polydimethylsiloxane (PDMS) and ammonium-functionalized polysiloxane components via urea bonds. Aluminum plates were adhered using these polysiloxanes containing PDMS and catechol-functionalized polysiloxane (PS-Ph(OH)₂) components at the compositional ratios of 9 : 1, 8 : 2, 7 : 3, 6 : 4 and 5 : 5 (PDMS-PS-Ph(OH)₂ (9 : 1, 8 : 2, 7 : 3, 6 : 4 and 5 : 5), respectively), and adhesion was evaluated via tensile shear tests at room temperature. The aluminum plates adhered using PDMS-PS-Ph(OH)₂ (8 : 2, 7 : 3, 6 : 4 and 5 : 5) exhibited high adhesive strength, withstanding tensile shear stresses of 12.7–21.7 MPa. Moreover, PDMS-PS-Ph(OH)₂ (8 : 2 and 7 : 3) maintained strong adhesion under impact loads. Furthermore, when a 5 kg weight was suspended from the aluminum plates adhered using PDMS-PS-Ph(OH)₂ (8 : 2 and 7 : 3) and the entire assembly was subsequently heated in an oven, the plates did not peel off until the temperature reached 180 °C and 190 °C, respectively, indicating that adhesion was maintained even at relatively high temperatures. Additionally, adherend plates possessing different thermal expansion coefficients, such as aluminum and stainless-steel plates, were adhered using PDMS-PS-Ph(OH)₂ (8 : 2 and 7 : 3). Thereafter, a 5 kg weight was suspended from the plates, and the temperature was cycled between room temperature and 150 °C. Consequently, the plates did not peel off, suggesting that PDMS-PS-Ph(OH)₂ (8 : 2 and 7 : 3) could effectively achieve adhesion between dissimilar materials.