A simple one-step approach to the decoration of parylene C coatings using functional silica-based NPs

Both pure silica (SiO₂) nanoparticles (SNPs) and functionalized hybrid thiophene-silica nanoparticles (H-SiO₂-Th NPs) were deposited onto non-functional parylene C films using a novel, readily executed, one-step decoration method. Unlike previously known methods, this functionalization method of parylene C films required neither a binding agent nor sophisticated equipment/devices. The SiO₂-based NPs anchored on parylene C substrates were formed via a common base-catalyzed hydrolytic sol-gel method. Regarding the mechanism, it has been assumed that the SiO₂ phase precursor (Si(OEt)₄, tetraethyl orthosilicate (TEOS), was first adsorbed and 2D polymerized onto the parylene C film due to hydrophobic interactions that served as an anchor mechanism for further NP growth. This assumption was investigated by comparing thermal behaviors (measured by differential scanning calorimetry, DSC) of parylene C coatings before and after the following specific surface treatment, i.e., (i) first parylene C coating incubation with TEOS followed by (ii) SNP formation and growth from such a TEOS-modified coating surface. Following the same procedure, hybrid thiophene-containing H-SiO₂-Th NPs were also successfully grown from the surface of a TEOS-modified parylene C film and characterized using high-resolution scanning electron microscopy (HR-SEM) and X-ray photoelectron spectroscopy (XPS). In order to obtain deeper insight into the overall functionalization process, the similar hybrid H-SiO₂-Th NPs that formed in the bulk contacting medium were also isolated and fully characterized for comparison needs.