Study On The Preparation And Aqueous Solution Properties Of Alkoxylated Carboxymethyl Starch Ether

Carboxymethyl starch（CMS）has been widely used in industrial and agricultural production because of its low cost,easy availability,good biocompatibility,certain thickening and surface activity.However,CMS has low viscosity as a thickener and weak surface activity as a polymer surfactant,so its application field is limited.In this paper,carboxymethyl starch ethers(AGCMS-C_4,AGCMS-C_8-10,AGCMS-Bn)were synthesized from industrial carboxymethyl starch by one-step reaction with alkoxyglycidyl ethers(C₄,C_8-10,Bn),and the relationship between their structure and properties was systematically investigated in order to improve their application properties.In this paper,the commercial CMS(DS_CM=0.32,viscosity:200～400 m Pa·s)and n-butyl glycidyl ether（BGE）were etherified by one-step etherification reaction to prepare butoxycarboxymethyl starch ether.n（BGE）:n(AGU_CM)=0.58 was fixed.The better synthesis conditions were determined through orthogonal experiment and single factor experiment.Under this optimal condition,a series of carboxymethyl starch ethers(AGCMS-C₄、AGCMS-C_8-10、AGCMS-Bn)with different degrees of substitution were prepared(the solvents used for the preparation of AGCMS-C_8-10and AGCMS-Bn were water ethanol mixed solvents),and their structures were determined by ¹H NMR and IR.The relationship between the structure and viscosity properties of carboxymethyl starch was studied.The results showed that when the hydrophobic group was C₄or Bn,the degree of substitution as high as 0.45 did not significantly improve the viscosity;When the carbon chain in the hydrophobic group is long(C_8-10),it only needs a small degree of substitution（MS=0.073）and the viscosity can reach 4.62 times that of the original CMS solution.Taking AGCMS-C_8-10(MS_C8-10=0.073)with the best viscosity performance as an example,the effects of p H,salt content,rotating speed and storage time on the viscosity performance of its aqueous solution were explored in detail.The experimental results show that the viscosity of the aqueous solution of carboxymethyl starch ether(AGCMS-C_8-10)can still be maintained at1253m Pa·s at p H=5;Its fluidity and shear resistance are better than those of the original CMS solution,and its dissolution time is greatly reduced.At the same time,the effects of hydrophobic group substitution degree and product concentration on the surface tension of AGCMS aqueous solution were investigated.The experimental results showed that AGCMS(C_8-10,Bn)had better surface activity than carboxymethyl starch,and the surface tension could be reduced to 32.88 m N/m.An oil in water lotion was prepared with AGCMS-C_8-10(DS_CM=0.32,MS_C8-10=0.073)as emulsifier,water as continuous phase and liquid paraffin as discontinuous phase.The effects of emulsifier concentration,oil-water ratio,p H value and salt concentration on the emulsifying properties of lotion were investigated in detail.The results showed that the higher the concentration of emulsifier,the better the stability of lotion;The optimum oil-water ratio is40:60（m L/m L）.The lotion has better stability under acidic and salt conditions,and can be stored stably for more than 190 D.