Fourier transform IR spectra have been used to study thermotropic phase transition of the naphthalene quaternary ammonium derivative, CnNaPh(1, 5)C6N+-H2O (I) (n = 16, 12, 10, 8, 6, and 4) (a choline analog) binary system at different temps. The experimental results suggest that the phase transition temps. of these bilayers can be observed by the drastic changes of the frequencies, relative intensities and half bandwidth of the nasCH2, nsCH2 band of alkyl chain in bilayers. The phase transition temperature was increased with increasing length of the alkyl tail chain. The gel-to-liq. crystal phase transition can be confirmed by the frequency shift. Finally, the structural units of the aggregates and the influences on the length of alkyl chain were further discussed from the change of bands of FT-IR.

Key words: BINARY SYSTEM, NAPHTHALENE P, BROMIDE, PHASE TRANSFORMATION, BILAYER MEMBRANE, METHONIUM COMPOUNDS