The Synthesis and Formation of Bi- and Tri-dentate Chelating Poly(ethylene glycol)-Terminated Self-Assembled Monolayers of Gold

Polyethylene glycol (PEG) has been used since the 1980’s to generate non-fouling or protein-resistant surfaces.  Shortly thereafter, scientists began to test oligo-ethylene glycol terminated self-assembled monolayers (SAMs) to inhibit protein adsorption.  Further investigation into the mechanism of non-fouling surfaces resulted in the finding of several key insights about PEG-thiols: (1) the protein-resistant behavior depends on the manner in which the molecules assemble on the surface, (2) the final state of the monolayer on the surface depends on solvent, temperature, and time, and (3) less ordered monolayers are more protein-resistant than highly ordered, crystalline monolayers.  Previous studies revealed that SAMs generated from chelating alkane trithiols exhibited enhanced film disorder and increased thermal stability.  To this end, we targeted the synthesis of two oligo-ethylene glycol trithiols having the chemical formulas of HO(CH₂O)_nCH₂C(CH₂SH)₃, where n = 3,4 to test their protein-resistant behavior and thermal stability.