Photoinduced Deadhesion of a Polymer Film Using a Photochromic Donor-Acceptor Stenhouse Adduct

Photoisomerization of molecules dissolved in a polymer film can modulate its properties. In a previous paper (Mostafavi, S. H.;et al. Macromolecules 2018, 51, 2388-2394), it was found that the ultraviolet light-induced photoisomerization of spiropyran dopants could substantially increase adhesion to a glass surface. In this work, a different photochromic reaction, the visible-light-induced cyclization of a donor-acceptor Stenhouse adduct (DASA), leads to the opposite effect: the deadhesion of a polystyrene film from a clean glass surface. Measurements of the shear and pull-off adhesion strengths before and after visible irradiation show a light-induced decrease of 20-30%. The time required for delamination in water shows an even more dramatic decrease of 90%. Changes in the water contact angle and other measurements suggest that molecular-level noncovalent interactions between the polymer and glass are weakened after photoisomerization, possibly due to the molecular contraction of the DASA that disrupts the interaction between its amine groups and the surface silanols. The ability to reduce polymer adhesion using visible light enables the controlled release of dye molecules from a glass container, where these have been stored as a dry powder, into an aqueous solution. Embedding photochromic molecules in a polymer can lead to new effects that may have practical applications in stimuli-responsive materials.