Effect of Silica Surface on Thermal Decomposition of the Immobilized Peroxide Oligomers

The thermal decomposition of pendant peroxy groups in a cooligomer of maleic anhydride with 5-(tertbutylperoxy)-5-methylhex-1-en-3-yne as well as in its amino derivatives immobilized on different silica surfaces, has been investigated using a complex thermogravimetric analysis. Two types of silica: fumed (aerosil) and precipitated (white carbon black) ones have been surface modified by this cooligomer via diverse techniques. It has been established that in all the cases the cooligomer decomposition on the silica surface complies with the first-order kinetics. Estimated activation energy evidences lowering thermal stability of the immobilized peroxide cooligomer in comparison with its decomposition in a solution. Interestingly, on the surface of fumed silica the decomposition of peroxide cooligomers always occurs as a one-stage process, while on the surface of precipitated silica it can occur as a two-stage process. The reason for this phenomenon is a difference in the porosity and surface chemistry of these two silica samples.