Polyelectrolyte complexes (PECs) have been prepared by mixing solution
s of carboxymethyl starch and diethylethylamino starch at ionic substi
tuent mixing ratios of 0.2, 0.5, and 0.8. The complexes were insoluble
in water, although they did swell to some extent. Interactions betwee
n ionic groups were examined using turbidity measurements and FTIR spe
ctroscopy. 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 appro
ximately 0.10M. These results indicate that complex formation was due
to ionic crosslinks between the oppositely charged starch molecules.