The surface structure and hydrophobic recovery of poly-dimethylsioxane insulator after Ar plasma treatment

Abstract

The effect of small molecules in poly(dimethyl siloxane) (PDMS) on the hydrophobic recovery has been studied. Soxhlet extraction was employed to remove the small molecules. The original and extracted samples were probed by positron annihilation and scanning electron microscopy (SEM). The results confirmed that the surface of unmodified PDMS is covered by the small molecules. PDMS with varying octamethylsiloxane (D4) contentwas modified by argon plasma. The variation of contact angle with the ageing time for different samples was studied by contact angle measurement. As a result it was shown that all the samples can recover to the original hydrophobic surface state after sufficient ageing time. Samples with higher D4 content exhibit a faster hydrophobic recovery. For the sample extracted first and then plasma modified, the hydrophobic recovery rate is very low, and such samples did not return to the untreated hydrophobic state.