Modified melamines and melamine resins for E/Z-isomerization

A new four-step synthetic-route for combining azochromophores with melamine resins was developed and their potential for E/Z-isomerization were shown by Kelvin-probe technique. Despite of other melamine resins, the basis molecule of the synthesized melamine–chromophore and the resulting melamine–chromophore resins is the 2,4,6-trichloro-1,3,5-triazine, the cyanuric chloride. In the first step, the azochromophore was bonded to the s-triazine-ring. Then, the residual chlorines of this triazine–chromophore were substituted by ammonia or primary amines. In the third step, formaldehyde was added, leading to melamine–chromophore monomers. For increasing the stability and the solubility of these monomers the reactive methylolgroups were etherificated with methyl or butyl alcohol. The result of these systems is a crosslinkable melamine–chromophore monomer which is converted in a resin by thermal treating or by acids. An optically induced switching of two different melamine–chromophore monomers and the resins were monitored by measuring the surface potential. It was done by Kelvin-probe technique. The results show a high surface potential difference between the cis- and the trans-state of the azo-group-systems, depending first on the attached chromophore and second whether the prepared films are monomer-layers or resins.