Raman system for on-line monitoring and optimisation of hybrid polymer gelation

Authors designed and built a Raman spectroscopic system for non-invasive, remote, on-line monitoring of gelation, which is the first step of a sol-gel process used for synthesis of hybrid polymers for photonics. The system was connected with typical glass reaction vessel. Suitable design of an optical system reduced excitation of interfering Raman signal in the wall of the reactor. Application of two excitation wavelengths reduced influence of fluorescence on measurements and provided high efficiency of the Raman system in wide range extending from 200 to 3500 cm⁻¹. Synthesised materials were based on silane precursors having epoxy and amino functionality. Raman spectroscopy enabled strict control over molecular structure of the materials during the polymerization process. Time and efficiency of monomers hydrolysis were measured. Products of this reaction were evaluated. The obtained data enabled us optimisation of the process parameters which ensured high efficiency of hydrolysis and subsequent control of solution viscosity. Moreover, behaviour of amine groups and epoxy rings was investigated and influence of water and solvents was found.