Studies On The Preparation And Properties Of Carboxymethyl Starch And Its Amide Derivatives

Hydrophobic modified products of starch and their derivatives have good physical and chemical properties.They are widely used in petroleum exploiting,paper making,soil improvement,wastewater treatment,etc.And they show promising prospects in various areas. In this thesis,a series of amide derivatives of carboxymethyl corn starch(CMCSa) were synthesized through the reaction of carboxymethyl corn starch(CMCS) with different amines which were selected as the hydrophobic reagent.Synthesis and properties of CMCS and CMCSa were studied.A high degree of substitution(DS=2.2) carboxymethyl corn starch(CMCS) was prepared by one-step carboxymethylation.The effects of the amounts of sodium hydroxide, reaction medium,reaction temperature,reaction time on the degree of substitution(DS_cm) and reaction efficiency(RE_cm) were studied.When the molar ratio of starch to chloroacetic acid was 4,the optimum reaction conditions were that the molar ratio of sodium hydroxide to chloroacetic acid was 2.5,reaction temperature was 50℃,reaction time was 2h and the amount of water in isopropyl alcohol was 2ml,CMCS prepared under optimal conditions showed the highest DS_cm and RE_cm,which were 2.2 and 55%,respectively.CMCS with different DS_cm from 1.69 to 2.55 was also prepared under the same reaction conditions and the RE_cm obtained was also above 55%.In addition,CMCS was characterized by IR spectra. CMCSa with different degree of substitution(DSa) of hydrophobic groups can be prepared from ammonium salt but the complicated oxidative degradation and crosslinking restrict the discussion of the results.So CMSa was prepared by reaction of CMCS with DCC DMAP and amines under mild reaction conditions.The effects of the amounts of DCC,DMAP amines, reaction medium,reaction temperature and reaction time on degree of substitution(DS_a) and reaction efficiency(RE_a) were studied,n(H₂SO₄):n(DCC)=1.5,n(DMAP):n(DCC)=0.05, reaction temperature 30℃,reaction time 24h,the molar ratio of DCC to amine was 1,the amount of DMSO 15mL/g were the optimal reaction conditions.REa of the CMCSa prepared under the optimal conditions got to 40%.In addition,CMCSa was characterized by IR spectra.The chelation of heavy metal of CMCS was investigated,the behaviors were also compared with that of CMCS(DS_cm=1).And viscosity behaviors and surface properties of the CMSa were also studied.