Supuramolecular Structure of Self-assembly Fabricated with Novel Aromatic Polyether on Si-wafers

Abstract

A new synthetic polymer of aromatic polyether (APE), having a narrow distribution of molecular weight, formed a specific self-assembly of Langmuir film (L film) on a water surface, which was subjected to surface pressure relaxation when the L film was compressed over 16.5 mN m -1 at 15 . This self-assembly was capable of transferring on silicon-wafers as LB films. We found that, because the XRD patterns for fabricated LB films depended on the crystal face of the silicon-wafer used and moreover increased in diffraction intensity with the increasing number of built-up layers in the LB film, the present LB films showed a kind of epitaxy-like phenomenon. We propose the molecular mechanism explaining that the formation of an ionic supuramolecular structure of APE occurs only on a silicon wafer surface. (RIGAKU,, and AFM and SEM images for LB film were observed by atomic force microscope (Digital Instruments, Nano Scope IIIa) and scanning electron microscope (Hitachi, S-4100), respectively. XPS measurements were performed on a JEOL JPS-9010 with a magnesium filament operating at 10 kV, 10 mA, using the Ka line. 3When a chloroform solution of APE was spread on a water surface without any additive reagents in water subphase, the APE polymer formed a stable Langmuir film (L film) having a transition point. The p-A curves for the APE L film were measured between 5 and 45 on a water surface with surface compression rate of 5 mm min -1 . By the common technique, LB film of APE was fabricated from the L film with transfer rate of 2 mm min -1 at 15 on various kinds of substrates, for instance, Si-wafers, optical glass, CaF 2 , copper plate, mica, and quartz glass. The Siwafer surface consisted of five kinds of crystal faces; [111] RESULTS3 1 p A The APE L film on the pure water surface gave a stable p-A curve with a transition point. The transition pressure increased with increasing inverse temperature; i.e., the transition is exothermic (-36.0 kJ mol -1 ), in contrast with an endothermic transition for L film of the usual fatty acids 20) . This exothermic character may be attributed to the selfassembly of APE molecules on the water surface. After the L film was compressed up to 30 mN m -1 with 5 mm min -1 , the surface pressure of the compressed L film relaxed with time even the surface area remained constant at 15 .shows the results of the surface relaxation at various pressures of initial compression. Equilibrium pressure was established at 16.5 mN m -1 after about 2 hr at 15 . However, when the film was compressed to the pressure less than the transition pressure, the phenomenon of surface relaxation was not clearly recognized. These phenomena suggest that the APE L film would be converted spontaneously into some different kinds of physical states with the progress of surface relaxation. 2In order to investigate the physical state of APE film after surface relaxation, the L films before and after transition were respectively transferred to one layer on the [111] face of Si-wafer. LB film was fabricated on the ...