Preparation And Properties Of Trimethylsilyl Starch Ether

Starch has attracted tremendous interests for its advantages such as abundant source, low cost, lack of toxicity, storage stability, good biodegradability and biocompatability. Although there are lots of hydrophilic groups in starch molecule, hydrogen bonds are formed by hydroxyls through intermolecular and intramolecular interaction. As a result, starch is insoluble in cold water and has low solubility in organic solvent. In order to improve the application performance of starch, chemical modification methods should be used to make starch soluble in organic solvents and has hydrophobic properties so that the application fields of starch can be greatly broaden.Starch are imparted to many new properties for its silylation, such as solubility, hydrophobicity and thermostability. Because of the compact structure of starch granule, there are only a tiny amount of surface hydroxyl groups can react with organosilicon reagents, it's not enough to change the performance of the starch. Therefore, it's necessary to use degraded starch to react with organosilicon reagents.Degraded starch was prepared after gelatinizing. The native starch was gelatinized at 90 V for 1h and then degraded for 5 h by 0.5 M HC1 at 60 ?.With waxy corn degraded starch as raw materials, hexamethyldisilazane (HMDS) as silylating agent, Cu(NO3)2·3H2O as catalyst, N,N-dimethyl formamide(DMF) as solvent, trimethylsilyl starch ether was prepared with hydrophobic modification. Temperature, amount of catalyst was studied respectively to evaluate their influences to the reaction, involving conversion rate of HMDS, DS of products and reaction efficiency. The mole ratio of HMDS and AGU was also disscused in this paper to study its influence on degree of substitution(DS) of products. When the temperatur was 80?, starch dispersion concentration was 10%(w/v), the mole percent of Cu(NO3)2·3H2O and HMDS was 2.1%, trimethylsilyl starch ether with different DS was prepared by adding different amount of HMDS. Finally, the prepared products were characterized by FT-IR and H NMR.The solubility, hydrophobicity and thermal stability of prepared trimethylsilyl starch ether were studied. The results showed that for trimethylsilyl starch ether with DS=2.68, its solubility(g/100g sovlent) in THF, chloroform and acetone was 33.4,20.5,26.2 respectively. Strong hydrophobicity was obtained and its maximum contact angle could reach to 130.88°. The trimethylsilyl starch ether also has good thermal stability, its maximum degradation temperature was 408?. For the products with DS=1.63 and DS=2.59, their glass-transition temperature was 89.9 ? and 109.1? respectively.