The Preparation And Properties Of PH Responsive3-carboxymethyl Thiopropyl Starch

Allyl starch was synthesized by environmentally friendly process using allyl bromide as hydrophobic reagent, water as solvent and sodium hydroxide as a catalyst. The reaction conditions were investigated and optimized. Optimum conditions were obtained as follows: n(allyl bromide):n(AGU)=l:l, amount of catalytical NaOH was n(NaOH):n(AGU)=1.5:l, amount of solvent was m(H2O):m(AGU)=3:l, reaction time was4h, reaction temperature was40°C. The DS of the products were determined by’H-NMR.Under those conditions, different DS of allyl starch were prepared. When DS reached0.8,the allyl starch shows themo-sensitive.The lower critical temperature (LCST) of Allyl starch can be easily adjusted at desired temperature between37and43°C by controlling the concentration of allyl starch solution. The surface tensions of aqueous solution of allyl starch have been investigated. The critical micelle concentrations (cmc) of allyl starch were in range of50mg/L to200mg/L depended on DS.3-carboxymethyl thiopropyl starch(CMTPS) were synthesized by thiol-ene addition reaction using different DS allyl starch.CMTPS showed pH-responsive properties. They were characterized by IR.’H-NMR. The DS of the products were determined by’H-NMR and the peak of double bond disappeared. The Critical phase separation pH point(CPP) of CMTPS can be adjusted by degree subsititution of CMTPS.The conductivity curve in titration process show the ionization equilibrium of carboxylic acid in solution. The micellar self-assembly behavior of pH responsive materials CMTPS were studied by fluorescence techniques and dynamic light scattering. When the solution pH changed from alkaline to acidic,Fluorescence peak shift to high wavelength. The micelle aggregation with hydrophobic core were formed. Micelle size mutated in the range of3.0-3.4. The surface tensions and zeta potential of aqueous solutions of CMTPS have been investigated at different pH. Zeta potential have great relevance with stability of the product in aqueous solution.