Synthesis And Properties Of 3-Alkoxy-2-hydroxypropyl Carboxymethyl Starch

Hydrophobic modification of starch and its derivatives is an effective method to improve and extend the application properties of starch chemicals.In the present work,a water-soluble hydrophobic starch-3-alkoxy-2-hydroxypropyl carboxymethyl starch(C₄,C₈,C₁₂)which has hydrophobic and hydrophilic property was designed and synthesized.The target product was synthesized first by reaction corn starch with alkyl glycidyl ether(C₄,C₈,C₁₂)to introduce hydrophobic group,then reaction with chloroactic acid to introduce hydrophilic group carboxymethyl sodium.The relationship between structure and properties of the target were systematically studied.Taken the reaction between corn starch and butyl glycidyl ether(BGE)as an example, the reaction conditions of starch with alkyl glycidyl ether were investigated and optimized, the optimal reaction conditions were:23.5%of starch slurry,60 mass percentage of isopropanol in mixtures of isopropanol and water,sodium hydroxide as catalytical alkali,0.40 of molar ratio of sodium hydroxide to starch,and refluxing five hours.Under those conditions, different of 3-alkoxy-2-hydroxypropyl starch of different drgree of substitution of hydrophobic group were prepared.The substitution of hydrophobic group(MS)of the products was determined by a method of Zeisel reaction and gas chromatography.Based on the above results,3-alkoxy-2- hydroxypropyl starches were carboxymethylated by chloroactic acid to prepare different degree of substitution(DS)of 3-alkoxy-2-hydroxypropyl carboxymethyl starch(AHPCMS).Those products were characterized by FT-IR.The effects of DS of carboxymethyl sodium,hydrophobic group,the concentration of sodium of chloride,temperature,rotation speed,maturing and relaxating time on the viscosity property of AHPCMS were investigated.The introduction of hydrophobic group into carboxymethyl starch(CMS)made it have well thickening property,the viscosity of AHPCMS could raise to 4.7 times with that of the corresponding CMS;when the mass percentage of NaCl was raised from 0%to 0.4%,the loss of viscosity of AHPCMS could reduce 17.7%compared with the corresponding CMS;1.8 weight percentage aqueous solution of AHPCMS which had a MS_C4of 0.242 and DS of carboxymethyl sodium of 0.66 had a favorable thickening property when the temperature was raised from 31℃to 55℃. AHPCMS possessed a certain resistance of shareing,compared with CMS.The viscosity of AHPCMS was firstly increased then decreased when maturing and relaxating time were increased.The effects of DS of carboxyrnethyl sodium,hydrophobic group,the concentration on surface tension of aqueous solution of AHPCMS were investigated.AHPCMS possessed favorable surface activity compared with CMS.When the concentration of AHPCMS was 0.300g per 100mL,the surface tension of aqueous solution of AHPCMS could achieve 32.23mN/m,which was equivalent to surfactant with low molecular weight.