Synthesis And Properties Of Novel PH-responsive S-triazine Starch Ether

In this study, based on acidic and alkaline responsiveness of tertiary amino and carboxyl groups, pH-responsive s-triazine tertiary amine starch ether and amphoteric starch were designed and synthesized by introduction of tertiary amino groups and carboxyl groups into starch using cyanuric chloride as an analyte. The synthetic conditions, properties of aqueous solutions and applications of the products were studied in detail. It provided a new idea to synthesize pH-responsive starch-based functional material, and developed high-performance and high value-added starch-based material with potential applications.Firstly, etherifying agent2,4-bis(dimethylamino)-6-chloro-[1,3,5]-triazine (BDAT) containing two tertiary amine was synthesized by nucleophilic substitution reaction between dimethylamine and cyanuric chloride. The effect of reaction conditions on the yield of BDAT was thoroughly studied. The highest yield of the BDAT reached94%. The structure of the product was confirmed by IR,1H NMR,13C NMR and MS spectroscopy. Then, BDAT was grafted to starch to form a new tertiary amine starch ether2,4-bis(dimethylamino)-[1,3,5]-triazine-6-yl)-starch (BDATS) via etherification reaction. The maximum degree of substitution (DS) and reaction efficiency (RE) were1.01and68.0%, respectively. The structure of the starch derivatives was confirmed by IR and13C NMR spectroscopy. BDATS demonstrated reversible pH responsiveness in aqueous solution. Solution properties of the obtained BDATS, such as transmittance, Zeta-potential, surface tension and viscosity, were measured as a function of pH. The critical pH of the solution shifted to a low pH by increasing DS of the BDATS.Amphoteric etherifying agent2,4-diglycino-6-chloro-[1,3,5]-triazine (CDT) was synthesized via nucleophilic substitution reaction between glycine and cyanuric chloride. Its structure was confirmed by IR,13C NMR and MS spectroscopy. A new amphoteric starch ether2,4-diglycino-[1,3,5]-triazine-6-yl)-starch (CDTS) was prepared via etherification between starch and2,4-diglycino-6-chloro-[1,3,5]-triazine. The maximum DS and RE were0.88and73.4%, respectively. The structure of the starch derivatives was confirmed by IR. The transmittance of CDTS solution showed the characteristic U-shaped distribution relative to the pH. Phase transition can occur at and around the isoelectric point (IEP) of the ampholytic polymers, leading to decrease of Zeta potential and solution transmittance. Furthermore. pH-responsive properties of the solution can be controlled by regulating DS of CDTS. BDATS was used as flocculant for removal of three anionic dyes from water. It was found that coagulation mechanisms were electrostatic neutralization and bridge between the dyes and the flocculants. The maximum color removal ratios of99.5%,97.9%and98.4%were observed at pH2, and the maximum flocculation capacity was1158mg/g for RR141,873mg/g for AR1and2296mg/g for AB324for cationic starch with degree of substitution0.63. The spent flocculant can be regenerated efficiently using alkaline solution at pH8. Repeated flocculation/regeneration study showed that flocculant can be regenerated and reused over ten successive cycles. After ten cycles of flocculation/regeneration, the average color removal ratio for the three dyes exceeded96%, and the recovery ratio of the flocculant was above75%.