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)-3,3,4,4,5,5hexafluoro-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. Nanoindentation and heating experiments suggest that the limited reversibility results from changes in polymer internal structure. We hypothesize that the adhesion changes arise from localized polymer and molecular motions that eliminate void spaces and surface gaps at the polymer−glass interface. The results show that adhesive forces between a prototypical polymer and an inorganic substrate can be modulated by photochromic reactions of embedded molecules.

Stimuli-responsive temporary adhesives: enabling debonding on demand through strategic molecular design

“…42 Although the central focus of this section is to discuss triggering debonding, we note that UV light may also be used to enhance adhesive strength. 69,70 A report from Bardeen and coworkers revealed that UV light can initiate molecular and polymeric movements, which ultimately improves adhesion by increasing interactions at the adhesive-substrate interface. 69 Adhesive liquication via photoisomerization…”

“…69,70 A report from Bardeen and coworkers revealed that UV light can initiate molecular and polymeric movements, which ultimately improves adhesion by increasing interactions at the adhesive-substrate interface. 69 Adhesive liquication via photoisomerization…”

“…[64][65][66][67] Alternatively, a stimulus may affect adhesive interactions (e.g., preferential formation of adhesive-stimuli interactions relative to adhesiveadherend interactions). [68][69][70][71]…”

Supramolecular adhesive materials from small‐molecule self‐assembly

“…However, the adhesion reversibility is limited by the permanent changes in the internal polymeric structure. 96 Therefore, high-molecularweight polymer adhesives often find it difficult to achieve a complete debonding and a full recovery due to their high viscosities, which calls for the development of SSSA.…”

Learning from Spiropyrans: How to Make Further Developments of Donor‐Acceptor Stenhouse Adducts

“…Bardeen and co‐workers embedded SPs into polystyrene (PS) film, and found that UV light irradiation increased the shear strength between the PS film and glass wafer by a factor of 7, due to the closed ‐to‐ open isomerization of SPs. [ 79 ] However, the adhesive force could not completely switch back, because the isomerization of SPs drove the PS chains motion, which further eliminated void spaces and surface gaps at the polymer‐glass interface. An extended system was realized by Read de Alaniz and co‐workers using DASAs as the photoresponsive molecules.…”