A new photoimaging system based on a trisdiazonium salt as a photocrosslinker for sulfonated polyelectrolytes

A photocrosslinker based on a trisdiazonium salt has been synthesized from 4,4′,4″-triaminotriphenylamine. Polyelectrolyte complexes can be obtained by mixing the trisdiazonium crosslinker with poly(styrenesulfonate) (PSS). The polyelectrolyte complex precipitates when PSS is added in an ionic ratio of around 1:1 to a trisdiazonium salt solution. However, the addition of an excess of PSS to the mixture leads to redissolution of the precipitate. A mixture of PSS and the photocrosslinker (27 wt.%) can be processed from solution to give thin films by spin coating. When the films are irradiated with UV light, a change in the solubility of the material is observed, which is due to the decomposition of diazonium groups and the transformation of the ionic bond into a covalent one, which in turn transforms the polyelectrolyte complex into a covalent network. The process has been characterized by UV and IR spectroscopy. Photoimaging experiments have been performed on this material and polymeric relief structures have been obtained through a photolithographic process.