Study On Staining Behavior Of Polymer By Ruthenium Tetroxide

This study concentrates on the behavior of ruthenium tetroxide (RuO₄) staining on some polymers such as polyglycol (PEG), nylon 6 and polystyrene (PS). The reason of the staining and the effect of the staining behavior on the thermo-stability of these polymers have been analyzed in this dissertation.The behavior of RuO₄ staining on PEG has been studied via fourier transform infrared (FTIR), gelatinous chromatogram (GC) and differential thermogravimetric (DTG). It has been found that PEG can be oxidized by RuO₄ to ester, carboxyl acid or carboxylate. The thermo-stability of PEG has been improved after being stained, which results in the ability of PEG to bear the electron beam in the observation of the transmission electron microscope (TEM). Meanwhile, RuO₄ is reduced to RuO₂. RuO₂ remains on the surface of PEG,which improves the ability of the specimen to scatter electron. As a result, the TEM image contrast of polymers can be improved through the RuO₄ staining.It has been found that there are nanocrystals on the surface of nylon 6 after being stained by RuO₄, which suggests that the staining of RuO₄ is in nano-scale. It has also been found through the measurement of the staining depth that the strong crosslink occurs on the stained layer of nylon 6. The stained layer is an obstacle to further diffusion of the staining agent. The staining mechanism has been studied via FTIR and X-ray electron spectrum (XPS). The mechanism is that the functional groups of CH₂ of nylon 6 which link to N can be oxidized to ester and carboxylate.When PS is stained by RuO₄, the reaction of crosslink occurs among some functional groups on the PS molecule chain, which brings the solidifying effect to PS. The crosslink and solidifying prevent RuO₄ from diffusing deeper. Therefore, Ru is assembled on the surface of PS, which heightens the ability of the specimen to scatter electron and reaches the staining purpose. The reaction mechanism between PS and RuCU is complicated and has been studied via FTIR and XPS. The mechanism is that crosslink happens between the adjacent benzene rings and RuO₂ is produced.