The effect of electrostatic fields on an oligo(ethylene glycol) molecule: dipole moments, polarizabilities and field dissociation

We calculate polarizabilities, dipole moments and structural changes of methoxy- and hydroxy-terminated oligo(ethylene glycol) (OEG) in both the helical and the planar ‘all trans’ conformers using ab initio methods. It is found that the helical form undergoes electrostriction with the establishment of additional, crosslinking hydrogen bonds in fields of the order and larger than 1 V Å−1. Electric fields of similar strength are capable of substantially changing the orientation of the head groups making the topmost oxygen atoms either buried or exposed depending on the field polarity. Field dissociation in fields of 2 V Å−1 is followed in detail. The implications of these findings for OEG terminated alkanethiol self-assembled monolayer will be studied in the next paper using energy minimization and Monte Carlo techniques