Scaling description of network structure of gelatin film surfaces

The surface structure of films prepared from aqueous gelatin solutions with concentrations c = 1.5, 3.0, and 6.0 g/dl at 293 K was studied by an elect ron microscopy method using decoration with gold. The parameters of physica l networks such as the values of period L, lattice density rho(s), and frac tal dimension D of clusters at various scales were determined on the basis of the lattice model. Network lattice density diminishes with an increase i n the characteristic radius R in accordance with the law rho(s) similar to RD-2 and remains virtually unchanged at the scale R > L/2, where L = 300-42 0 Angstrom. As the concentration rises, the fractal dimension D of clusters increases from 1.63 to 1.80 at the scale 2R < L; D = 1.95-2.0 at 2R > L. T he period L of the network is close to the hydrodynamic radius (R) of macro molecule aggregates in aqueous solution near the gelation threshold c* appr oximate to 1.5 g/dl; the cluster fractal dimension at the film surfaces at the scale 2R < L is equal to 5/3 and coincides with that of macromolecule a ggregates in aqueous gels at c < c*.