Nanocomposites and nanomaterials

Effects of silicon dioxide on the properties of dye-doped aromatic polyurethane nanocomposites
V.I. Bezrodnyi1,  A.M. Negriyko1, T.V. Bezrodna1, L.F. Kosyanchuk2
1Photoactivity Department, Institute of Physics, Natl. Acad. of Sci. of Ukraine. Prospect Nauki, 46, Kiev-03028, Ukraine. 
E-mail: bezrod@iop.kiev.ua
2Institute of Macromolecular Chemistry, Natl. Acad. of Sci. of Ukraine, 
Kharkovskoe av.,48, Kiev-02160, Ukraine

Composite materials based on the organic dye doped polymers with silicon dioxide nanoparticles are of a special interest for the development of quantum electronics optical devices. Their key parameter is operation lifetime, which depends on the dye stability in the solid medium during both storage and operation.
This work concerns the studies of hybrid polyurethane acrylate matrices, activated by a organoluminophor Rhodamine 6G and doped with silicon dioxide nanoparticles. The composite material was produced by a radical photopolymerization method in a form of the sandwich structure between optical substrates. To obtain optically homogeneous samples, the problem of silicon dioxide uniform distribution in the polymer matrix was solved. The specific methods (along with frontal photopolimerization) were developed in order to prevent nanoparticle agglomeration in the initial mixture, and also during polymerization process.
Silicon dioxide nanoparticles were found out to increase stability of organic dyes in the elastic polymer matrices, based on polyurethane acrylate. Large concentrations (~2x10-2 mol/l) of the Rhodamine dyes cause the formation of not only dye monomers, but also different associates, namely, dimers, trimers and J‑aggregates. Nanoparticle inclusion to the polymer results in a low tendency for the dye molecules to the self-aggregation, because silicon dioxide increases considerably dielectric permeability of the polymer matrix.
Photostability growth is also caused by a decrease of free volume fraction in the elastic polymers by silicon dioxide nanoparticles; this factor hinders connecting of the dye molecules with reacting particles (singlet oxygen, radicals etc.).
In summary, new nanocomposite optical polymer materials were developed on a base of polyurethane acrylate and silicon dioxide nanoparticles. The investigations of their structure and properties showed that they can be successfully applied in the production of efficient solid-state active media for the tunable lasers based on the organic compounds.