The impact of fluorination on the structure and properties of self-assembled monolayer films

Abstract

The adsorption of partially fluorinated amphiphiles on metal/metal oxide surfaces allows for the generation of specifically fluorinated thin-film interfaces. Such surfaces are often compared to polytetrafluoroethylene (PTFE), which exhibits a low surface energy, accompanied by biological and chemical inertness, making perfluorinated interfaces applicable to a wide range of technologies. In thin-film research, self-assembled monolayers derived from fluorinated alkanethiols (FSAMs) serve as well-defined systems that can be used to evaluate the physical and chemical properties of interfaces produced with varying degrees of fluorination. The characteristics of these surfaces have been attributed to both the chemical composition of the individual molecular adsorbates and the consequent structural features associated with monolayers formed from these unique partially fluorinated adsorbates. Specifically, this review seeks to correlate the structural and interfacial properties of FSAMs on gold with the structure/composition of the fluorinated moiety present in the adsorbed molecules and to highlight how the degree of fluorination influences the interfacial ordering of the individual alkanethiolate chains and the vacuum energy levels of the modified metal substrate. Additionally, the thermal stability of these organic thin films is analyzed as a function of adsorbate structure. Included are highlights of some of the studies in which FSAMs, formed from a variety of new types of surfactants, were used to modify colloidal systems, to generate anti-adhesive materials, and to enhance the stability of fluorinated thin films toward low-energy electron degradation.