Abstract
A new four-step synthetic-route for combining chromophores with melamine
resins was developed and practized.
Despite of other melamine resins, the basis 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 an aldehyde 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 butylalcohol.
The mass-spectra give evidence that the modified melamine precondensates are
monomers and no mixture of different oligomers like else in melamine-aldehyde
prepolymers. Though the result of these systems is a crosslinkable
melamine-chromophore monomer which is converted in a resin by heating or under acid conditions. It
is remarkable that these polymers show an excellent thermal stability with a
decomposition temperature far beyond 300°:C, a great advantage for using them a
s optical materials.
Resins, which build homogenous amorphous and highly transparent films, were
achieved by thermal treating of the melamine-chromophore-resins.
The reaction steps were monitored by online-IR-spectroscopy, which has enabled
to find and optimize the reaction conditions of the syntheses steps. Furthermore
the characteristic changing IR-bands and time-reaction-profiles were extracted.
Concerning their usability in second order nonlinear optics the alignment of the
dipoles was investigated by applying a corona discharge. Simultaneously to the
poling process, the monomers were polycondensated by thermal heating. The
continuously measured UV/Vis-absorptions of the poled polymer films have demonstrated
that the absorption of the film have fallen within the first weeks after poling.
An electric potential from 10 till 20 V could be measured during this period,
indicating orientation processes of the poled films.
The E/Z-switching behaviour of the azo-groups were investigated by Kelvin-Probe.
The results have demonstrated that the new monomers and polymers are potential
candidates for optical switching processes. The fixing of thioles on the
triazine-chromophores of the first reaction step has been made successfully.
E/Z-switchings of self-assembled monolayers of the azo-triazine-thioles on gold have
indicated that these monolayers need only a few seconds for an isomerization
process. | 
