| Abstract: | Poly(ethylene oxide) (PEO) was crystallized on alkali halides, such as NaCl, KCl, and KBr, from solution in isopentyl acetate. PEO dendrites first formed on alkali halide surfaces and grew to sheet the whole surface. Individual fibrils consisting of dendrites were arranged with the preferred orientation in the <110> direction on KBr and KCl, and mainly in the <100> direction on NaCl. Tetragonal lamellae grew not on the substrate directly but on the sheet platelet only, establishing a homoepitaxial relationship to the dendrites. Because the dendritic sheet that intervened between them controlled the orientation of the lamellae, tetragonal lamellae formed with a preferred orientation on alkali halide surfaces. The dendrites had morphological features of fractals, i.e., diffusion-limited aggregates (DLA). Their morphology was controlled by the diffusion process of polymer molecules on the substrate surface, as well as by epitaxial interaction. The fractal dimension (D) was obtained by analyzing the dendrites by taking the autocorrelation function of density: D ranges from 1.6 to 1.8, depending on the crystallization conditions, such as the kinds of substrate and crystallization temperature. |
