有限层Langmuir-Blodgett类晶型薄膜微观结构与超分子结构的小角X射线散射研究

本文应用SAXS与微机模型拟合(MCMI)研究了-LB(S为芪唑杰)薄膜与SA-LB(SA为芪唑盐/花生酸镉)薄膜的微观结构与超分子结构, 以及这类LB薄膜凝聚态不稳定的原因。结果指出: 第一, 从π-A曲线可知, S与A的脂肪链可以类似于脂肪酸晶胞形成二维类晶系结构; 第二, 随着分子比R~M=S/A=0到1, S和A之间发生了人分散相至连续相的相逆转; 第三, S在二维类晶系中处于不稳定的近似伸直型的高能态构象,然而, 哑铃形的芪唑基类似于芪趋向于作倾斜状密堆砌, S的两条脂肪链则倾向于转变为稳定的全反式燕尾开的低能态构象, 仅占S分子长约2/3的脂肪链亦降低了S分子间与S-A分子间的凝聚力, 这就导致了S连续相的二维类晶系存在大量晶格缺陷, 故只能形成4~6层不稳定的Y型LB薄膜; 第四, 存放一月后, 这种不稳定的S连续相的层状超分子结构极易存坏和崩塌。

Studies on SAXS on the microstructure and superstructure of finite-layer langmuir-blodgeet crystal-like films. II the mixed film systems of stibazium salt and cadmium arachidate

Stilbazium iodide (symboled as S) has high b values and was used to prepare LB films, but the deposition properties of S and the stabilities of S-LB films are very poor. The mixed systems of stilbazium salt and cadmium arachidate (symboled as SA, the mol. ratio RM = S/A = 0 to 1) can improve the deposition property, but the stability of SA-LB films are still poor. The present work is to investigate the microstructure and superstructure of S-LB and SA-LB films, and the reason of unstability of these films by SAXS and MCMI. The results are as follows. First, the fatty chains of both stilbazium salt and cadmium arachidate can form a crystal-like structure of two-dimension as same as the usual fatty acid. Second, the phase-inversion of S and A from dispersed phase to continuous phase occurs as Rm changes from 0 to 1. Third, in the crystal-like of two-dimension S-mols. are in high energy and full-straighten conformation, but the stilbazium group of dumbbell-shape tends to pile up in the oblique and close packing form two fatty chains of S tend to extend in the lower energy trans-form and swallow tail conformation; the length of the fatty chains (C16) is about 2/3 length of S-mol., so the mol. forces between SS or S-AS are less than of usual fatty acid and Y-type LB films of S continuous phase are unstable. Fourth, a lot of lattice defect exist in two-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 prepared and these layers' structure collapse after 1 mo.