CORRELATION BETWEEN ORGANIC CONTENT, CURING PROCESS AND OPTO-MECHANICAL PROPERTIES OF HYBRID ORGANIC/INORGANIC POLYMER

Fast sol gel (FSG) technique facilitates the manufacture of organically modified ceramics by wet chemistry, producing high density stable monoliths quickly. The physical properties can be determined by different precursors combinations.

This work focuses on preparation and characterization of different FSG compositions as a function of the inorganic/organic molar ratio. The monolith fabrication was based on three precursors, tetramethoxysilane (TMOS) – forming inorganic phase only, methyltrimethoxysilane (MTMS) – forming 75% of inorganic phase and 25% of organic free group, and Methacryloxypropyltrimethoxysilane (MAPTMS) - forming 75% of inorganic phase and 25% of functional long organic group. A series of FSG monoliths with different material compositions was synthesized. The organic content varied from 17-52 weight percentage (wt.%). The samples were characterized by various methods.

The range of precursors molar ratio needed to form monoliths was established. We have found that the effect of organic content on the refractive index is dependent on the quantity, type and functionality of the organic phase. Both thermal and UV curing promoted the formation of the inorganic network resulting in increase in the refractive index.

We have defined and presented the precursors ratio effect on the thermal expansion. The thermal expansion coefficient increased with the organic content under thermal curing. Samples that were UV cured demonstrated that as the ratio of the fully cross-linked precursors increases, thermal expansion decreases, regardless of the organic content wt.%. The weight loss of the samples was found to be less than 2.5% up to 200°C. The materials have non porous surface and great tensile strength, ~10Mpa. The results obtained will guide us in future fabrication of useful optical materials for adhesive and encapsulation applications.