Noncovalent Photochromic Polymer Adhesion

Abstract

This paper explores whether the photochromic reaction of a molecule embedded in a polymer film can affect its surface adhesion properties, as measured by shear strength and delamination in water. The adherence of polystyrene (PS) to glass was chosen as a model system. Two commercially available photochromes—a spiropyran derivative 1′,3′-dihydro-1′,3′,3′-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2′-(2H)-indole]) (SP) and a diarylethene derivative 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl)-3,3,4,4,5,5-hexafluoro-1-cyclopentene (DAE)—are studied in detail. Both photochromic reactions can significantly enhance the adhesion of PS to a glass surface. The most dramatic results were obtained for PS/SP films, whose shear strength increased by a factor of 7 while the delamination rate was suppressed by at least 2 orders of magnitude after exposure to UV light. The enhanced polymer adhesion could only be partially reversed, even after extended exposure to visible light completely regenerated the UV-absorbing isomer. Na...