Stimuli-responsive thiol-epoxy networks with photo-switchable bulk and surface properties

Abstract

Photo-responsive thiol-epoxy click networks with spatially controllable solubility and surface wettability were prepared and characterized in detail.

Laser‐Triggered Writing and Biofunctionalization of Thiol‐Ene Networks

“…At prolonged UV exposure, a re‐crosslinking of the cleaved polymer chains is observed through secondary reactions (e.g., formation of azobenzene groups by dimerization of nitroso‐benzaldehyde moieties) that leads to an increase in the gel content. [ 16–21 ]…”

“…In addition, the photoresponsive nature of the o ‐NBE links in thiol‐ene click networks was used for altering the surface properties in a spatially controlled way. In previous works, we used the presence of polar species such as carboxylic acids, that are formed upon photocleavage, in order to switch the surface polarity of thin polymer films, [ 16 ] showing also the possibility to move a water droplet on the irradiated surface. [ 17 ]…”

“…[ 15 ] In previous studies, we explored the possibility to introduce o ‐NBE moieties in a wide range of different networks such as epoxy and methacrylic ones as well as thiol‐ene, thiol‐epoxy and thiol‐yne polymer networks fabricated by click chemistry. [ 16–20 ] In this context, thiol‐ene networks containing o ‐NBE moieties were used as positive/negative tone photoresist with good resolution. [ 21 ] In addition to the use of o ‐NBE for producing photoresists, we also showed the possibility to modify surface properties of the network through UV‐induced photocleavage, by exploiting the formation of polar species such as carboxylic acids.…”

“…[ 21 ] In addition to the use of o ‐NBE for producing photoresists, we also showed the possibility to modify surface properties of the network through UV‐induced photocleavage, by exploiting the formation of polar species such as carboxylic acids. [ 16 ] The high control obtained by light‐irradiation was further employed to move water droplets on gradually irradiated photopolymer surfaces. [ 17 ]…”

“…[ 22 ] Here we also evidence that the use of a laser source for activating the cleavage reaction is of particular interest since it allows not only high spatial control but also enables dry development (i.e., removal of cleaved molecules without the use of a solvent) while typically solvents are required to remove the soluble species formed in the exposed areas. [ 15–20,23,24 ]…”