Polymerization Kinetics of Methacrylic Groups in Organic-Inorganic Hybrid Polymeric Thin Films
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1007-S10-02
Polymerization Kinetics of Methacrylic Groups in Organic-Inorganic Hybrid Polymeric Thin Films Congji Zha, Xinshi Luo, and Barry Luther-Davies Center for Ultrahigh Bandwidth Devices for Optical Systems, Laser Physics Centre, The Australian National University, Research School of Physical Sciences and Engineering, Canberra, ACT 0200, Australia ABSTRACT In this paper, the polymerization kinetics of unsaturated double bonds (C=C) in TiO2- and ZrO2-doped hybrid polymeric thin films during UV irradiation and thermal curing is studied by monitoring the variation of C=C absorption band at 1630 cm-1 using FT-IR spectroscopic technique. Experimental results showed that polymerization of the unsaturated C=C groups in the TiO2- and ZrO2-doped hybrid polymers can be realized by either photo-irradiation or thermal treatment. The UV-induced polymerization process is much faster than thermal curing, but a full conversion of C=C groups into polyacrylate chains cannot be achieved without thermal treatment. The catalytic effect of TiO2 and ZrO2 on promoting the polymerization of C=C groups was observed, and the time of UV exposure and thermal curing for cross-linking C=C bonds was found to decrease with the increase of the concentration of TiO2 and ZrO2. The activation energy of the hybrid material containing varied concentration of TiO2 and ZrO2 was calculated, and the results indicated that TiO2 is more active than ZrO2 in promoting the polymerization of the unsaturated C=C bonds. Finally, the mechanisms for TiO2 and ZrO2 enhancing the material’s photosensitivity (i.e. promoting polymerization of C=C bonds) have been proposed and discussed. 1. INTRODUCTION Fabrication of integrated optical components and devices using photosensitive organicinorganic hybrid polymers has attracted considerable attention in recent years [1-3], because hybrid polymeric thin films can be fabricated by spin-coating process, and waveguide structure can be easily defined on these polymeric films by direct laser-writing or UVprinting process, enabling low cost fabrication of photonic chips and devices. It is known that waveguide fabrication using photolithographic process usually requires the unsaturated C=C bonds in the hybrid thin films to be sufficiently cross-linked upon UV irradiation, thus understanding the polymerization kinetics of these bonds in the hybrid material network is of interest, because the determination of parameters, such as photo-initiator type and concentration, UV power density and dose, thermal curing temperature and time for waveguide patterning requires us to understand the process of polymerization. Recently we developed an anhydrous sol-gel process for synthesis of TiO2- and ZrO2-doped hybrid polymers and demonstrated the material’s promising optical properties, such as linear thermo-optic coefficients, low birefringence and low optical absorption losses [4-6]. In this paper, the polymerization kinetics of unsaturated double bonds (C=C) in TiO2- and ZrO2doped hybrid polymeric thin films during UV irradiation and the
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