EFFECT OF POLYCATION IN SUBPHASE ON AGGREGATION STRUCTURE OF MONOLAYER AND LANGMUIR-BLODGETT-FILM OF ANIONIC AMPHIPHILE

The aggregation structure of the monolayers prepared from an anionic amphiphile (2C14SNa) and 2C14S/poly(ethylenimine) (PEI) complex at the subphase temperature of 293 K was investigated on the basis of electron microscopic observations. The aggregation structure and surface properties of the Langmuir-Blodgett (LB) films prepared from those monolayers were also investigated by means of X-ray diffraction. Fourier transform infrared attenuated total reflection (FT-IR-ATR) spectroscopy and X-ray photoelectron spectroscopy (XPS). 2C14SNa monolayer was crystallized by compression on the water surface (compressing crystallized monolayer). For crystallization of the 2C14SNa monolayer, higher surface pressure was required because of the strong repulsion among the hydrophilic groups of the 2C14SNa molecules. The formation of polyion complex between amphiphile and PEI effectively affected the aggregation states of the monolayer on the water surface. Owing to the formation of polyion complex, the repulsive force among the hydrophilic group of anionic amphiphiles was effectively reduced and the monolayer could be crystallized without compression. Also, the transfer ratio of the monolayer onto the substrate approached unity by the addition of PEI into water subphase. Wide-angle X-ray diffraction, FT-IR, and XPS results indicated the existence of an ultrathin polymer layer between the 2C14S monolayers.