SAXS and DSC studies on the structural characteristics of siliconized s-triazine glassy hybrid materials

Three hybrid materials composed of planar s-triazine rings and polyhedral silica (SiO₂), phenylsilsesquioxane (PhSiO_1.5) and diphenylsiloxane (Ph₂SiO) building blocks were investigated by differential scanning calorimetry (DSC) and small angle X-ray scattering (SAXS) techniques. These measurements revealed that the geometrically dissimilar components were fully integrated into intact glassy hybrid structures. Their DSC thermograms showed that these hybrids are thermally stable below 350 °C with moderate glass transition temperatures (T_g) of 56–110 °C consistent with the increasing structural connectivity of the silicone component. The SAXS data was analyzed to obtain different structural information using Porod, Guinier and Kratky approximations. The general features of each of the SAXS profiles of these hybrids are very similar to those of polyphenylsilsesquioxane (PPhSQ). The SAXS profiles reveal that these hybrids can be described as nano-scale primary particles that are self-organized in macromolecular ensembles to form extended unfolded textures of varying scattering lengths (91–168 Å). The obtained hybrid particles adopt either 3-D bulk fractals with open structures or 2-D surface fractals with dense cores. The short interfacial thickness (< 3 Å) and the low thermal fluctuation parameters strongly suggest that these particles are held together by substantial cohesion forces.