Design of ultrahydrophobic surface by surface initiated atom transfer radical polymerization technique

In this study, surface-initiated atom transfer radical polymerization (SI-ATRP) of laurylacrylate (LA) and octadecylacrylate (ODA) on silicon wafer conducted in attempt to create controllable ultrahyrophobic brushes. The initiator-immobilized substrate, was prepared by the esterification of hydroxyl groups on silicon wafer with 2-bromopropionyl bromide (2-BPB); followed by the ATRP of LA and ODA using a catalyst system i.e., Cu(I)Br / N, N, N?, N??, N??-pentamethyldiethylenetriamine (PMDETA). The resulting ultrahydrophobic brushes were characterized by in-situ reflactance fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), ellipsometry, gel permation chromatography (GPC) and water contact angle measurements. From the ellipsometry and GPC measurements, the grafting densities (chains / nm2) of PLA and PODA brushes on silicon wafer were found to be 0,28 and 0,34, respectively.Number average molecular weight and polydispersity index of these PLA and PODA polymers were determinated by GPC. AFM results also showed that the SI-ATRP method suggest to obtain homogeneous polymer brushes.In this study, we have particularly focused on the ultrahydrophobic characters of the PLA and PODA on silicon wafer surface. As a result, the surfaces with PLA and PODA exhibitied water contact angles as high as 163o and 171o, respectively.