Carbonate-Terminated Self-Assembled Monolayers for Mimicking Nanoscale Polycarbonate Surfaces

Two carbonate-terminated alkanethiol molecules having different positional isomers of a six-membered cyclic carbonate group, 3-COC12SH and 2-COC12SH, were synthesized and used to generate self-assembled monolayers (SAMs) on gold to serve as mimics of the surfaces of commercially available poly(propylene carbonate) (PPC) and poly(ethylene carbonate) (PEC). The adsorbate molecules were characterized using ¹H and ¹³C nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry. The corresponding SAMs on gold were characterized by ellipsometry, contact angle goniometry, polarization-modulation infrared reflection-adsorption spectroscopy, and X-ray photoelectron spectroscopy. The contact angle data showed that the wettabilities of both SAMs were largely similar to each other and to the PEC samples for a wide range of contacting probe liquids (with water correlating particularly well with PEC and both SAMs). As a whole, the wettability data suggest that the carbonate-terminated SAMs can serve as mimics of nanoscale polycarbonate surfaces and can be used to investigate the interfacial properties of polycarbonates without interference from the surface reconstruction.