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

Fourier transform infrared reflection absorption spectroscopy (FT-IRRAS) ha s been used to study the protein resistance of poly- and oligo(ethylene gly col) (PEG and OEG) terminated alkanethiolate self-assembled monolayers (SAM s) on Au and Ag in the temperature range from 0 to 85 degreesC. These exper iments extend previous room-temperature studies by Harder et al. I who rela ted the protein adsorption characteristics of OEG-SAMs to the lateral densi ty and corresponding molecular conformation of the ethylene glycol (EG) moi eties in the film. In addition to the short oligomer OEG-SAMs, we investiga ted PEG-derivatized alkanethiolate monolayers with an average chain length of 45 EG units and a mean molecular mass of 2000 g/mol (PEG2000). We observ e that films, which are protein resistant at room temperature, maintain the ir protein repulsive characteristics up to 85 degreesC but may adsorb signi ficant amounts of protein if the temperature is lowered.