Complexes of Oppositely Charged Ionic Starches

Polyelectrolyte complexes (PECs) have been prepared by mixing solutions of carboxymethyl starch and diethylethylamino starch at ionic substituent mixing ratios of 0.2, 0.5, and 0.8. The complexes were insoluble in water, although they did swell to some extent. Interactions between ionic groups were examined using turbidity measurements and FTIR spectroscopy. Supernatant turbidity was the lowest when the mixing ratio was equal to 0.5. The degree of carboxylate neutralization as measured by FTIR increased with mixing ratio. Complex formation was completely suppressed when NaCl was present in concentrations greater than approximately 0.10m. These results indicate that complex formation was due to ionic crosslinks between the oppositely charged starch molecules.