Synthesis And Properties Of Alipatic/Aromatic Amine Schiff-bases Of Dialdehyde Starch

In this study, aryl or alkyl groups were introduced to dialdehyde starch (DAS) by C=N based on the high reactive aldehyde groups of DAS, and the Schiff-bases of DAS were obtained. The formation of C=N partially destroyed the acetal or hemiacetal structure of DAS, and gave the starch derivatives proper hydrophilic/hydrophobic balance by released hydroxyl groups and aryl (or alkyl) groups, then the resulting water-soluble Schiff-bases of DAS could show surface activities, and the resulting water-insoluble ones with the degree of substitution (DS) of aryl (alkyl) groups could show metal ion adsorption capacity. Surface tension, foaming behavior, stability in hard water and emulsifying capacity of water-soluble Schiff-bases of DAS had also been measured, and the water-insoluble Schiff-bases of DAS had been used as sorbent to remove Cu(II) and Pb(II) ions in aqueous solution. The synthesis conditions of Schiff-bases of DAS were also studied.The synthesis conditions of aniline Schiff-bases of DAS (DAS-ANs) were optimized to achieve the highest reaction efficiency with acetic acid as catalyst in dimethyl sulfoxide (DMSO) homogeneous system. These optimized synthesis conditions were applied to synthesize other Schiff-bases between DAS and oil-soluble amino reactants, such as benzylamine (BN), phenethylamine (PEA), n-hexylamine (HA) and n-octylamine (OA). The water solubility of Schiff-bases of DAS with oil-soluble amine were researched. It demonstrated that the water solubility was between1.80-2.00g·1OOg-1when the DS of oil-soluble amine was less than0.2, and they were insoluble in water when the DS of oil-soluble amine was greater than0.2. m-Aminophenol (AP) Schiff-bases of DAS were synthesized in water, and the highest reaction efficiency was65%. The synthesized DAS-APs were all insoluble in water. The structures of all Schiff-bases of DAS were characterized by FT-IR, NMR and XRD.Surface tension, foaming behavior, stability in hard water and emulsifying capacity of water-soluble alipatic/aromatic amine Schiff-bases of DAS had been measured, and the effect of aryl and alkyl groups on surface tension had been studied. When the DS of hydrophobic groups was less than0.2, the surface tension at critical aggregation concentration (γCAC) of DAS-ANs, DAS-BNs, DAS-PEAs, DAS-HAs and DAS-OAs was58.25,47.96,46.27,38.03and36.17mN-m-1at1.66,0.62,0.31,0.33and0.23g·L-1, respectively. These data suggested that (1) the surface tension of alipatic amine Schiff-bases of DAS was less than that of aromatic amine Schiff-bases of DAS;(2) the increase of alkyl chain length among homologues, such as BN and PEA, or HA and OA, did not affected yCAC obviously, but the critical aggregation concentration (CAC) decreased as the hydrophobicity of alkyl or aryl groups increased. The γCAC and CAC of DAS-ANs were different from that of DAS-BNs and DAS-PEAs. The foaming behavior showed that the foaming power of water-soluble alipatic/aromatic amine Schiff-bases of DAS increased as the surface tension decreased, and the foam stability of alipatic amine Schiff-bases of DAS was better than that of aromatic amine Schiff-bases of DAS. The stability in hard water all reached the highest level.The adsorption studies of water-insoluble alipatic/aromatic amine Schiff-bases of DAS showed that:(1) there is good adsorption capacity of DAS-APs for Cu(II) and Pb(II);(2)2h was needed for the equilibrium of adsorption;(3) adsorption capacity increased as the DS of AP increased;(4) the maximum adsorption capacity for Cu(II)(pH5.3) and Pb(II)(pH4.0) were0.96mmol·g-1and2.34mmol·g-1, respectively.