Electrostatic charge effect on the orientational distribution of molecules on the water surface

The electrostatic charge effect on the orientational distribution of rod-like polar molecules at the air–water interface is analyzed taking into account the induced charge on electrode suspended in the air. The first order orientational order parameter S1 is found to change as the electrode approaches monolayers, and approximately expressed as S1=S10+A*(2S20−3S102+1)/3, where A* characterizes the effect of electrode and Si0 (i=1,2) represents orientational order parameters in the absence of suspended electrode. The molecular area giving the maximum deviation of S1 from S10 decreases as the interaction between molecules and water surface increases, but it is independent of the position of electrode.