STUDIES OF SAXS IN THE MICROSTRUCTURE AND SUPERSTRUCTURE OF FINITE-LAYER LANGMUIR-BLODGETT CRYSTAL-LIKE FILMS .2. THE MIXED FILM SYSTEMS OFSTILBAZIUM SALT AND CADMIUM ARACHIDATE

Stilbazium iodic, (symboled as S) has high beta value and has been use d to prepare. LB films, but the deposition properties of S and the sta bilities of S-LB films are very poor. The mixed systems of stilbazium salt and cadmium arachidate (symboled as SA, the molecular ratio R(M) = S/A = 0 to 1) can improve the deposition property, but, the stabilit y of SA-LB films are still poor. The present work is to investigate th e microstructure and superstructure of S-LB and SA-LB films, and the r eason of unstability of these films by SAXS and MCMI. The results are as follows. First, the fatty chains of both stilbazium salt and cadmiu m arachi date can form thecrystal-like structure of two-dimension as s ame as the usual fatty acid. Second, the phase-inversion of S and A fr om dispersed phase to continuous phase occurs as R(M) changes from 0 t o 1. Third, in the crystal-like of two-dimension S-molecules are in hi gh energy and full-straighten conformation, but the stilbazium group o f dumbbell-shape tends to pile up in the oblique and close packingform ; two fatty chains of S tend to extend in the lower energy trans-form and swallowtail conformation; the lengh of the fatty chains (C-16) is about 2/3 lengh of S-molecule, so the molecular forces between SSor S- AS are less than that of usual fatty acid and Y-type LB films of S con tinuous phase are unstable. Fourth, a lot of lattice defect exist in t wo-dimension crystal-like of SA-systems as mentioned above, so only 4 to 6 layers unstable and less regular Y-type SA-LB films could be prep ared and these layers' structure collapse after 1 month.