Temperature dependence of the protein resistance of poly- and oligo(ethylene glycol)-terminated alkanethiolate monolayers

Fourier transform infrared reflection absorption spectroscopy (FT-IRRAS) has been used to study the protein resistance of poly- and oligo(ethylene glycol) (PEG and OEG) terminated alkanethiolate self-assembled monolayers (SAMs) on Au and Ag in the temperature range from 0 to 85 °C. These experiments extend previous room-temperature studies by Harder et al.1 who related the protein adsorption characteristics of OEG-SAMs to the lateral density and corresponding molecular conformation of the ethylene glycol (EG) moieties in the film. In addition to the short oligomer OEG-SAMs, we investigated PEG-derivatized alkanethiolate monolayers with an average chain length of 45 EG units and a mean molecular mass of 2000 g/mol (PEG2000). We observe that films, which are protein resistant at room temperature, maintain their protein repulsive characteristics up to 85 °C but may adsorb significant amounts of protein if the temperature is lowered