Frictional electrification of Langmuir-Blodgett layers and dipole moment of constituent molecules of Langmuir layers

Triboelectrification of Langmuir-Blodgett films, which consist of various molecules with -CH₂NH₂, -COOCH₃, -CONH₂, -CH₂OH, -COOH and -CONHC₆H₅ bonded to -(CH2)₁₆CH₃ linear hydrocarbon chains, was investigated to make clear the influence of polar atomic groups on the contact or triboelectrification. Further, local electric dipole moment of each polar group was determined by measuring displacement currents generated by compressing monolayers on the water surface at 283K. The triboelectric series obtained from the frictional electrification between monolayers and glass by taking the polarity and magnitude was as follows: (+) -CH₂NH₂, -CH₂OH, -COOH, -CONHC₆H₅, Glass, -CONH₂, -COOCH₃ (-). The local dipole moments of atomic groups were 0.30, 0.26, 0.01, -0.20, (Glass), 0.17 and 0.34D in the order of material in the triboelectric series, respectively. The order of magnitude of dipole moment seems to correspond to the triboelectric series of atomic groups. This shows that the electron density on atomic groups affects the frictional electrification.