Polyhedral oligomeric silsesquioxanes (POSS) thermal degradation

The mechanism of thermal degradation of several substituted polyhedral oligomeric silsesquioxanes (POSS) cages is studied in this work. Hydrogen POSS and methyl POSS shows incomplete sublimation on heating, both in inert atmosphere and in air. Isobutyl and octyl substituted POSS undergo an almost complete evaporation when heated in inert atmosphere. In air, oxidation competes with volatilization, producing a considerable amount of silica-like residue on heating up to 800 °C. Phenyl POSS shows a higher thermal stability than saturated aliphatic POSS and limited volatility, producing a ceramic residue at high yield on heating in nitrogen, composed of a silica containing a considerable amount of free-carbon. A lower amount of residue is shown after heating in air, corresponding to the POSS Si-O fraction. A vinyl POSS cage/network resin is also studied, in comparison to above materials, showing the highest ceramic yield.