Mikko Keränen

UV light induced surface expansion phenomenon of hybrid glass thin films

Liquid-phase deposition of sol-gel method derived hybrid glass materials is utilized for fabrication of UV-light-sensitive thin films. The hybrid glass material undergoes a surface-relief deformation when exposed to UV light. The observed deformation phenomenon is in the form of a physical expansion of the exposed areas. The UV light induced surface expansion of the hybrid glass film was used to fabricate near-sinusoidal diffraction gratings with periods of 24 microm, 18 microm, 12 microm, and 9 microm. The maximum deformation when the material was patterned as a diffraction grating was 0.685 microm. The hybrid glass material features an index of refraction of 1.52 at 632.8 microm, rms surface roughness of 2.2 +/- 0.8 microm after processing, and extinction coefficients of 1.2 x 10-3 microm-1 and 0.47 x 10-3 mm-1 at wavelengths of 633 nm and 1550 nm, respectively.

Raman investigation of minor component reaction during polymer synthesis process

Raman spectorscopy was applied to study the reactions between amine and epoxy groups, which had been expected to proceed during synthesis of hybrid polymer based on three monomers: 3-aminopropyltrimethoxysilane, 3-glycidyloxypropyl-trimethoxysilane and methacryloxy-propyltrimethoxysilane. Efficiency of the investigated reaction determines the molecular structure of the organic network and consequently - mechanical and optical properties of manufactured material. An optical system developed for the real-time Raman monitoring was connected with typical glass reaction vessel and non-invasive measurements were made. Additional FT-Raman investigation was carried out to confirm obtained results. Transformation of primary amine as well as epoxy ring opening was confirmed and role of catalyzers was discussed.

Spectroscopic studies of a ring opening process between epoxy- and aminosilanes and imine formation reactions in aqueous solutions

AbstractNMR and Raman spectroscopy studies were performed for different 3-aminopropyl(trimethoxy)- and 3-glycidoxypropyl(trimethoxy)silane based sol-gel systems containing different ketones. Exceptionally stable imine products were obtained depending on a reaction system at alkaline pH conditions and in the presence of water. These imine formation reactions were carried out without further catalyst. In addition, effect of water for the epoxy ring opening process was demonstrated, as well as the effect of solvents for the reaction path was confirmed. The reaction between 3-aminopropyl(trimethoxy)- and 3-glycidoxypropyl(trimethoxy)silane needs additional catalyst to proceed fast or the reaction between the organic parts remains very slow. In case of isopropyl alcohol as the solvent, the result is the same. Water catalyses the organic and hydrolysation/condensation reactions. Ketones, like acetone initiates stable imine formation and water as a by-product methoxy group hydrolysation, but the epoxy groups remains unchanged after long periodHighlightsStable organosiloxane based imines were synthesised in the presence of water as a by-product and in a very alkaline conditions (pH ≥ 12).Synthesised and characterised amine/epoxy/ketone – sol-gel one-pot systems proved that ketones and amines form imines, as was expected, and these imines showed to be very stable in aqueous solutions and no drying agents, extraction or precursors having aromatic substituents were used during the syntheses.

Raman diagnostics in manufacturing of polymer planar optical waveguides

A Raman spectroscopy was used to diagnose a synthesis process of new class of materials - hybrid polymer thin films, dedicated to planar optical waveguides. Hybrids, made in sol-gel technology, have a great application potential, because their properties may be formed in wide range. However, to obtain high quality product, a strict control of the manufacturing process must be ensured. In our experiment, correctness of particular steps of the process as well as molecular structure of monomers, gel and thin films was investigated. The results of Raman mesurements showed that efficiency of two basic reactions should be improved. However, the structure of final product seems to be appropriate. To investigate full potential of Raman spectroscopy in process control, an experimental in-situ measurement was made in the real time, which allowed us to estimate the time required for the reaction.