Langmuir, Vol.30, No.34, 10263-10269, 2014
Helical versus All-Trans Conformations of Oligo(ethylene glycol)-Terminated Alkanethiol Self-Assembled Monolayers
The complex mixture of conformational states exhibited by oligo(ethylene glycol)-terminated alkanethiols on Ag and Au surfaces is explored by polarization-dependent Xray absorption spectroscopy. Three self-assembled monolayers (SAMs) with known helical or all-trans conformations are used as references to characterize a SAM with unknown conformations. This case study is used as a prototype for developing a systematic framework to extract the conformations of SAMs from the polarization dependence of several orbitals. In the case at hand, these are associated with the C-H/Rydberg bonds of the alkane, the C-H/Rydberg bonds of ethylene glycol, and the C-C bonds of the backbone. The C-H/Rydberg orbitals of the alkane and ethylene glycol are distinguished via the chemical shift of the corresponding C is core levels.