Sol-gel materials investigation by means of Raman spectroscopy

Raman spectroscopic studies were carried out to investigate the synthesis of hybrid polymers prepared for photonic applications by a sol-gel technology. The main reason for development of hybrid polymers is wide variety of controllable optical, mechanical and electrical properties which can be obtained by proper molecular design of used precursors. However, the precise control of hybrids molecular structure must be ensured during their production to obtain required properties. The main aim of research presented in this paper was to analyse the ability of Raman measurements to estimate the efficiency and correctness of particular stages of the technological process. Parameters of measurement systems adequate for hybrid material characterisation were found. Dedicated fibre optic system was attached to reaction glass vessel and on-line monitoring was being performed during the first step of the process - gelation. Background correction enabled on-line monitoring with presence of external light and consequently – precise control over addition of the ingredients as well as comparison between Raman spectra and viscosity of the material. Hybrid polymer thin films, after deposition on technological substrate, were studied by Raman microscopy. Efficiency and time of the most important reactions such as hydrolysis, epoxy ring opening, amine transformation, double bonds opening can be measured as well as thickness of thin films can be estimated. Moreover, Raman on-line monitoring enabled optimisation of gelation parameters and obtaining hydrolysis efficiency equal to 100% for system maintained in liquid form. It seems that Raman diagnostics makes synthesis of high quality sol-gel materials possible.