Publications

We observed the surface pressure (pi) - surface area (A) curves of the DNP-DPPE monolayers at an air/water interface. An overshoot-hump and an inflection point were markedly shown in the pi-A curve with a successive compression. To elucidate the mechanism of the characteristic changes in the curve, we measured the absorption spectra of the thin film which was deposited on a quartz plate using a Langmuir-Blodgett (LB) technique. It was found that the maximum peak in the spectrum shifted to longer wavelengths at 3 nm in the subsequent overshoot-hump, and that the peak intensity increased threefold after the inflection point. Therefore, it was considered that the overshoot-hump indicated a change of the conformation of the dinitrophenyl moiety in the DNP-DPPE molecule at an air/water interface, and that the inflection point reflected a collapse of the DNP-DPPE monolayer, respectively. To explain the mechanism of the overshoot-hump, we established a kinetic model which included a cooperative aggregation process between DNP-DPPE molecules during compression. The overshoot-hump was successfully reproduced with the help of computer simulation on the basis of this kinetic model.