Synthesis of amphiphilic amylose and starch derivatives

For non-food uses starch generally is modified in order to obtain products with properties suitable for various applications. In the present work, starch and amylose were hydrophobically modified through reactions with long-chain alpha -alkyl epoxides (C-6 and C-12) in DMSO solution, in the presence of NaH as a catalyst. The molar substitution (MS) was calculated from NMR spectra. Derivatives with high as well as low MS values were obtained. In order to reach MS values above 1.5, the reaction had to be run for 150-300 h. Viscosity and GPC measurements indicated that the polysaccharides were degraded in DMSO under the influence of methyl sulfinyl anion, which presumably is the active catalyst. The derivatives were also characterized by FTIR. The ratio between the peak areas for OH stretching and alkyl stretching vibrations, respectively, in the FTIR spectra, was found to be proportional to MS values determined from NMR spectra. The solubility of the hydrophobically modified polysaccharide in various solvents was tested. Samples having C-12-alkyl side chains and MS > 1 were soluble in toluene. The C6 derivatives were water soluble up to a MS value of 0.3. (C) 2002 Elsevier Science Ltd. All rights reserved.