FORMATION OF SELF-ASSEMBLED MONOLAYERS BY CHEMISORPTION OF DERIVATIVES OF OLIGO(ETHYLENE GLYCOL) OF STRUCTURE HS(CH2)11(OCH2CH2)META-OH ON GOLD

This paper describes the preparation of oligo(ethylene glycol)-terminated alkanethiols having structure HS-(CH2)11(OCH2CH)m(OH) (m = 3-7) and their use in their use in the formation of self-assembled monolayers (SAMs) on gold. A combination of experimental evidence derived from X-ray photoelectron spectroscopy (XPS), measurement of contact angles, and ellipsometry implies substantial disorder in the oligo(ethylene glycol)-containing segment. The order in the -(CH2)11-group is not defined by the available evidence. The SAMs are moderately hydrophilic: theta-a(H2O) = 34-38-degrees; theta-r(H2O) = 22-25-degrees. A study of monolayers containing mixtures of HS(CH2)11CH3 and HS(CH2)11(OCH2CH2)6OH suggests that the oligo(ethylene glycol) moieties are effective at preventing underlying methylene groups from influencing wetting by water. A limited study demonstrates that these oligo(ethylene glycol)-containing SAMs resist that adsorption of protein from solution and suggests that SAMS will be a useful model system model for studying the adsorption of proteins onto organic surfaces.