Thermogravimetric Studies of PMMA on Silica

The thermal degradation of poly(methyl methacrylate) (PMMA) has been studied extensively. It is well accepted that the degradation process is a radical chain reaction involving initiation, depropagation, transfer, and termination reactions. In the degradation process, the factors having observable effects on the decomposition behavior include molecular mass, polydispersity, tacticity, and sample dimensions. The effects of tacticity on the degradation behavior of PMMA were investigated by Kashiwagi et al., Jellinek et al. And Chiamtore et al. The results indicated that both isotactic and syndiotactic PMMA have similar decomposition pathways and activation energies. Isotactic PMMA will decompose at a slightly lower temperature and over a broader range, compared to syndiotactic PMMA with the similar chain ends and molecular masses. It has also been reported that isotactic PMMA is more sensitive to electron-beam radiation, namely, it degrades more easily, than syndiotactic PMMA. The PMMA-SiO2 system has been investigated by a few groups. The results indicated that the interaction between the carbonyl groups and silica surfaces can increase the decomposition temperature of PMMA. However, how different variables affect the decomposition behavior of PMMA is still far from clear. In the present work, we report studies of the degradation of ultrathin adsorbed PMMA on silica with a specific focus on the effects of adsorbed amount and tacticity on decomposition