the shape and size of macromolecules of carboxymethyl starch in diluted solutions

Abstract

Carboxymethyl starch samples were prepared by etherification in heterogeneous media. Three samples were prepared from corn starch and three samples from potato starch. Degree of substitution of prepared samples ranged from 0.40 to 1.10. The samples were investigated by static and dynamic light scattering and viscosity of diluted solution in 0.10 M NaCl as solvent at 25 C. The values of molar mass, MW, radius of gyration, Rg, hydrodynamic radius, Rh, and limited viscosity number, [η] were determined. It was found that the samples are similar to each other regardless of the type of starch and the degree of substitution. Fractal dimension, df, was equal to 2.380 (Rg - MW) and 2.406 (Rη - MW), while parameter was 1.195. The values of fractal dimension and parameter are characteristic values for the behavior of branched clusters in thermodynamically good solvents.

Keywords

• carboxymethyl starch
• static and dynamic light scattering
• viscosimetry
• branched clusters