Raman system for on-line monitoring and optimisation of hybrid polymer gelation M. GNYBA *1 , M. KERÄNEN 2 , A. MAANINEN 2 , J. SUHONEN 2 , M. JÊDRZEJEWSKA-SZCZERSKA 1 , B.B. KOSMOWSKI 1 , and P. WIERZBA 1 1 Gdañsk University of Technology, Department of Optoelectronics, 11/12 Narutowicza Str., 80-952 Gdañsk, Poland 2 VTT Electronics, Kaitoväylä 1, P.O. Box 1100, FIN-90571 Oulu, Finland 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 ef- ficiency 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 re- action 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 investi- gated and influence of water and solvents was found. Keywords: Raman spectroscopy, process monitoring, hybrid polymers, sol-gel technology. 1. Introduction Raman spectroscopy is a powerful and versatile research technique with a broad range of potential applications for industrial process control. Its scope of use in on-line pro- cess monitoring is limited by the fact that the measurement has to be performed on substances present in the processing equipment, rather than on a preconditioned sample using equipment which in most cases cannot operate in the pro- duction environment. As a result, the measurement equip- ment has to be located remotely from the processing equip- ment and a means of introducing intense laser light to the process equipment and collecting Raman scattered light have to be found. Addressing industrial requirements, ro- bust and cost-effective Raman setups should be developed to enhance application field of this technique. Moreover, each particular application requires reliable analysis of measurement conditions and subsequent Raman system ad- aptation. One of the most important field of Raman measure- ments use is development of new materials for photonics and other advanced technical applications. Requirements of modern photonics stimulate search of materials which have improved optical, mechanical and electrical properties. Consequently, several materials are being developed and synthesised using different technological processes. How- ever, one of the most modern trends in material science is development of whole groups of materials whose proper- ties can be changed in a wide range by suitable design of their molecular structure. Such a group of materials should be synthesised in the same technological process, while their properties are controlled by slight modifications of the synthesis parameters. Organically modified silanes (ORMOSILs) prepared in the sol-gel technology are one of the groups based on this concept. Incorporation of organic components into an inor- ganic silica network can provide coincidence of advantages of both groups of materials. In comparison with organic materials, hybrids have better thermal stability, scratch re- sistance and hardness, while their toughness and flexibility is better than properties of glasses. Moreover, ORMOSILs’ workability is very good. Hybrids can be used in photonics to manufacture planar waveguides, lenses, Bragg gratings and components for in- tegrated optics. Moreover, dielectric layers, coatings and packaging are produced from these materials. Research to apply them in optical fibre sensors (including bio-sensors) and solid state lasers is underway [1–5]. The main advantage of the sol-gel technology is the possibility of synthesis of sophisticated materials in a rela- tively simple, cost-effective and low-temperature process. This method enables us precise control of a precursor com- Opto-Electron. Rev., 13, no. 1, 2005 M. Gnyba 9 Contributed paper OPTO-ELECTRONICS REVIEW 13(1), 9–17 * e-mail: mgnyba@eti.pg.gda.pl