Fractal Structure of Polyacrylamide Gel by Atomic Force Microscopy
A polymer gel is a system composed of a three-dimensional network or an interpenetrating network in which molecular chains are cross-linked and polymerized with a solvent (usually water), similar to biological tissues. The crosslinked structure keeps it insoluble and maintains a certain shape; the presence of osmotic pressure causes it to swell to a volume equilibrium. The structure of such gels is difficult to observe with ordinary microscopes. Atomic force microscopy has the ability to detect the surface properties of samples while detecting the topography of the sample in the liquid and gas phases at nanometer resolution, and to test the sample during the test. The damage is small, so it is an important tool in the study of gel fractal structure. Microscopic image analysis of the microstructure of the inorganic cross-linked polyacrylamide gel was carried out by atomic force microscopy. It was found that whether in the organic or inorganic cross-linking system, and regardless of the concentration of polyacrylamide and cross-linking agent, the dendritic fractal images with self-similarity are finally formed on the micrometer scale. On a smaller scale, it is found that the individual small tree scorpion fractals are closely packed by nano-sized particles. In the colloidal state studied in the dispersion gel system, the formation of the dendritic fractal structure and its specific morphology depend on the concentration of polyacrylamide, and the presence or absence of the cross-linking agent and its influence on the geometry of the dendritic gel fractal.