Modified melamine resins for optical applications

A new four-step synthetic-route for combining chromophores with melamine resins was developed and their use for optical applications was demonstrated. Despite other melamine resins, the basic molecule of this system 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 precondensates. For increasing the stability and the solubility of these precondensates, the reactive methylolgroups were etherificated with methyl or butyl alcohol. One example of such a crosslinkable melamine-chromophore was illustrated and characterized by NMR- and mass-spectroscopy. The mass-spectrum gives evidence that the modified melamine precondensates are monomers and not a mixture of different oligomers like else in melamine-aldehyde prepolymers. The result of these systems is a crosslinkable melamine-chromophore monomer which is converted in a resin by thermal treating or by acids. It is remarkable that these polymers show an excellent thermal stability with a de-composition temperature beyond 300 degrees C, a great advantage for using them as optical materials. Their usability as second-order nonlinear optical material was investigated by corona poling. (C) 1999 Elsevier Science Inc. All rights reserved.