Modification of amylose and investigation of its inclusion behavior

Five different amylose derivatives—hydroxypropyl, hydroxyethyl, 1,2-dihydroxypropyl, acetyl and carboxymethyl amylose—with varying degrees of substitution were investigated concerning their water solubility and their complexing ability of iodine and of several organic compounds. In general, the water solubility of all samples increased with increasing degree of substitution, whereas their complexing ability decreased. This was examined by means of UV spectroscopy and circular dichroism. The three derivatives with substituents carrying hydroxy groups showed almost equivalent behavior, while acetylated amyloses revealed much more guest-specific complexing properties. A reduced complexing ability of the carboxymethylated amyloses is attributed to an enhanced substitution at the HO-3 and HO-6 groups disturbing the helical conformation of the amylose chain and lowering the complex stability. In addition, the pH dependence was determined for two samples of carboxymethyl amylose.