Probing Interfacial dynamics of plasma-induced hydrophobic recovery in HTV silicone rubber using sum frequency Generation-Vibrational Spectroscopy (SFG-VS)

Silicone rubber material has wide applications due to its hydrophobic recovery properties. Previous laboratory studies have shown that plasma jet treatment can quickly enhance the surface hydrophobicity of silicone rubber, but the unclear mechanism limits technology promotion. It is generally believed that the hydrophobic recovery process is affected by the surface hydrophobic groups content, but the related mechanism still requires further quantitative exploration. In this article, the hydrophobic properties and vibration spectra of HTV silicone rubber surface before and after low pressure plasma treatment were investigated by contact angle testing and sum frequency generation vibration spectroscopy (SFG-VS). It was found that the SFG-VS signal in the surface silicon methyl region was significantly weakened after treatment, and then showed a rising trend similar to the static contact angle with the increase of recovery time. Comparative experiments showed that the treatment time and the content of low-molecule-weight siloxanes (LMWs) in silicone rubber had an effect on the silicon methyl signal recovery rate. At the same time, according to the differences in methyl signal of cyclic and linear siloxane molecules, it was judged that the main source of the surface spectral signal of HTV silicone rubber was the silicon methyl of linear siloxane molecules.