Characterization of ozone-degraded composite of crosslinked polydimethylsiloxane with silica in water

Effect of ozone-charged water on degradation of silicone rubber, i.e., crosslinked polydimethylsiloxane/silica composite, was investigated by various analytical techniques, in which active species including active oxygen were generated by self-decomposition of ozone in water. The composite was less swollen with good solvent after degradation with ozone-charged water, whereas amount of extracted polydimethylsiloxane increased significantly, reflecting chain scission of the polymer. Hardness of the composite, measured with scanning probe microscope and hardness tester, was found to increase after degradation. The extracts were proved to be polydimethylsiloxane through FT-IR and GC-MS. The composite was characterized through DD/MAS and CP/MAS solid state NMR spectroscopies on 13C and 29Si nuclei. It was found that OSi(OH)(CH3) groups were made in polydimethylsiloxane due to oxidative reaction with hydroxyl radical and they were attracted to silica in the composite to result in the decrease in the swelling ratio and the increase in the hardness.