Enhancement of Two-Photon
Initiating
Efficiency of a 4,4′-Diaminostyryl-2,2′-bipyridine Derivative
Promoted by Complexation with Silver Ions
- Publication date
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Abstract
We report on the two-photon-induced polymerization (TPIP)
ability
of a new class of free radical two-photon initiator based on a cationic
silver(I) complex incorporating 4,4′-diaminostyryl-2,2′-bipyridine
(DES) derivatives as ligands. Coordination with Ag<sup>+</sup> induces
a strong increase of the charge transfer character at excited state,
which enhances the two-photon absorption properties of the complex
with respect to that of the free ligand. A comparative analysis of
the photophysical properties of DES and DES<sub>2</sub>Ag<sup>+</sup> shows that the presence of silver cation increases the efficiency
for the generation of radical cations (DES<sup>•+</sup>), which
can be used as hydrogen abstractor in free radical photopolymerization.
We show that the addition of an aliphatic amine used as hydrogen donor
also opens a parallel route for the regeneration of DES. The improvement
of the two-photon polymerization efficiency is then evidenced by the
fabrication of microstructures. We finally demonstrate that the use
of DES<sub>2</sub>Ag<sup>+</sup> as two-photon initiator offers new
opportunities for the fabrication of functional nanostructures composed
of metal–polymer nanocomposites