Effect of length of alkyl chain consisting of fluorine and carbon in self-assembled monolayers

Abstract

We investigated the interfacial properties of fluorocarbon self-assembled monolayers (FC-SAMs) with different alkyl chain lengths. It was found that the substrate characteristics were changed rapidly with the fabrication time and temperature of the SAM. FC-3SAM, which has the shortest alkyl chain in this study, showed a contact angle of 54.1 degrees when it was fabricated in an electric oven at 60 degrees C for the first minute. The FC-3SAM showed a contact angle of up to 76.9 degrees when it was fabricated in an electric oven at the same temperature condition for 180 minutes. FC-10SAM, which has the longest alkyl chain in this study, showed a contact angle of 64.7 degrees when it was fabricated at a temperature condition of 60 degrees C for 1 minute, and a contact angle of 98.7 degrees at a temperature condition of 60 degrees C for 180 minutes. It was found that the FC-10SAM shows an increased contact angle and hydrophobic properties due to a well-aligned molecular structure resulting from a strong van der Waals force. In contrast, the FC-3SAM shows a small contact angle due to the intermolecular disorder resulting from a weak van der Waals force. The average roughness of FC-SAMs was investigated using AFM. The surface roughness of FC-SAMs, which verifies the results of contact angle, was confirmed. At a fabrication time of 120 minutes, the FC-10SAM showed an improvement in average roughness by 62% compared to that of FC-3SAM due to its good alignment.