Showing papers by "Jian Jin published in 1998"

Characterization and structure of side-on azo copolymers in Langmuir-Blodgett films

Abstract: Three different azobenzene derivatives, namely, 2-(6-methacryloxyhexyloxy)-4-hexyloxy-4‘-hexyloxyazobenzene (A1) and poly{6-[5-hexyloxy-2-(4-hexyloxypheny)azophenyloxy]hexyl methacrylate}x-co-{2-hydroxyethyl methacrylate}y (A2, x = 0.8, y = 0.2), and (A3, x = 0.2, y = 0.8), have been synthesized to study the characterization of Langmuir monolayers at the air−water interface and the aggregation and orientation of Langmuir−Blodgett (LB) films on a solid substrate. The surface pressure−area isotherms showed that they could form well-defined condensed-type monolayers, with A1 and A2 undergoing conformational transition. The monolayers of A1 and A3 could be deposited onto substrate at 20 mN/m at 20 °C with a near unity transfer ratio. The polarized Fourier transform infrared and polarized UV−vis spectra revealed that LB films of A1 and A3 on substrates had in-plane orientation with the long axis of azobenzene moiety exhibiting a large tilt angle (42° and 35°, respectively) with respect to the substrate normal....

Formation of Branched Fractal CdS Patterns in Oligomer LB Monolayers: A Study Using Transmission Electron Microscopy

Abstract: Transmission electron microscopy images of the treelike fractal aggregates of CdS nanoparticles in amphiphilic oligomer (polymaleic acid with octadecanol ester) LB matrix were observed. The features of these aggregates were developed into the micrometer regime. By changing the ratio between carboxylic groups and hydrocarbon chains, as well as the surface pressure, different fractal CdS patterns could be obtained. These results lead us to propose the mechanism of the formation of branchlike patterns, very much analogous to two-dimensional irreversible fractal-growth models such as diffusion-limited aggregates (DLA). Weak hydrophobic and hydrophilic interaction for interfacial molecular recognition at the organic/inorganic interface had been proposed as providing a possible elucidation for the formation of some aspects of a self-similar fractal-like pattern. At a ratio of 7:1, the fractal dimension was calculated by the box-counting method, and the dominant value was 1.69 ± 0.03, which was in good agreement...