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

Abstract

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 S 1 is found to change as the electrode approaches monolayers, and approximately expressed as S 1= S 1 0+ A *(2 S 2 0−3 S 1 02+1)/3, where A * characterizes the effect of electrode and S i 0 (i=1,2) represents orientational order parameters in the absence of suspended electrode. The molecular area giving the maximum deviation of S 1 from S 1 0 decreases as the interaction between molecules and water surface increases, but it is independent of the position of electrode.