Preparation of poss-based hybrid networks via thiol-epoxy click chemistry

A series of hybrid networks based on polyhedral oligomeric silsesquioxane (POSS) were prepared by thiol-epoxy click reaction using commercially available octakis-glycidyl-POSS (G-POSS), trimethylolpropane triglycidyl ether and trimethylolpropane tris(3-mercaptopropionate) as monomers. The click reaction was simply catalyzed by lithium hydroxide and proceed readily at ambient conditions in very good yields. The incorporation of G-POSS in the network was clearly determined by transmission electron microscopy, FT-IR spectroscopy and 1H-NMR spectroscopy that performed with a model study using 1-butanethiol and G-POSS molecules. The homogenous distribution of G-POSS up to 5% wt in the hybrid network was apparently confirmed by morphological investigations. By increasing G-POSS content higher than 5% wt, the heterogeneous dispersion of G-POSS was determined from the tensile strength measurements. The significant decrease in tensile strength was possible due to the agglomeration of G-POSS. On the other hand, thermal properties of hybrid networks was by thermogravimetric and difference thermogravimetry analyses, where all samples exhibited one-step degradation in the range of 220-500 °C. The thermal decomposition of hybrid network led to complete degradation of the organic part and favored the formation of stable, carbonaceous and inorganic residues as char. Thus, the char yields of hybrid networks were increased 6.2, 7.8, 10.1, 12.7 and 15.1% by G-POSS loadings from 0 to 15% wt. This improvement was also a proof of the incorporation of G-POSS in the hybrid networks that provide high heat resistances compared to neat sample in the absence of G-POSS.