Synthesis And Characterization Of O-carboxymethyl Chitosan Grafted Colorants And Supported Catalysts

Owning to its excellent biocompatibility,O-carboxymethyl chitosan?OMCS?is always chosen as a carrier to graft edible colorant and fabricate polymeric colorant,which can avoid the uptake of edible colorants by human and improve their safety.In our work,a series of polymeric colorants were prepared via different synthetic routes by grafting the azo edible colorants and anthraquinone derivatives onto OMCS.The anti-reduction properties and cytotoxicity of these prepared polymeric colorants were evaluated.?1?Two polymeric colorants were fabricated by grafting sulfonyl chloride sunset yellow?SY?and allura red?AR?onto OMCS.The characterization results of FT-IR,¹H-NMR,gel chromatography and elemental analysis showed that these two azo colorants were grafted onto OMCS successfully,and their grafting degrees were29.1%and 33.3%,respectively.The NADH reduction and cytotoxicity test results showed that the anti-reduction property of prepared polymeric colorant was improved and its cytotoxicity was reduced.?2?The coupling compounds of three azo colorants SY,AR and amaranth?AM?were firstly sulfonyl chlorinated,and then grafted onto OMCS.Eventually,the grafted product was coupled with the diazonium salt to obtain polymeric colorants.The grafting degree of SY,AR and AM onto OMCS were determined to be 35.6%,46.9%and 44.8%,and the water solubility of three polymeric colorants were improved to be 9.2 g/100 g,7.4 g/100 g and 7.8 g/100 g due to the retainment of–SO₃H group in synthetic route.?3?Four polymeric colorants were prepared by grafting orange II,SY,carmine?CA?and AM onto OMCS using ethoxy group as bridge and the hydroxyl group of azo colorant as reactive site.The results showed that the grafting degree were 32.8%,31.6%,31.0%and 30.5%,respectively.In addition,the water solubility of prepared polymeric colorants were improved due to the hydrophily of ethoxy group.?4?Six anthraquinone polymeric colorants were fabricated by an Ullmann condensation reaction between brominated anthraquinone derivatives and OMCS.The cytotoxicity test results showed that IC50 values for these six polymeric colorants were all above 7.6 g/L,suggesting that the prepared polymeric colorants exhibited low cytotoxicity.The metal ions could be fixed by the coordination property of OMCS to realize the reuse of metal catalyst.?1?Two supported catalysts were prepared by the coordination of Pd and Ni ions onto OMCS.The analytic results of FT-IR,XRD,SEM-EDS and ICP showed that the Pd and Ni ions were grafted onto OMCS successfully and the loading amount were 8.3%and 8.9%respectively.The test results of Heck cross-coupling reaction between aryl halides and n-butyl acrylate catalyzed by fabricated catalysts showed that the obtained product yields for aryl iodides and aryl bromides were up to 99%and 96%respectively.After reusing for five times,the obtained product yield for Pd and Ni catalysts were still above 90%and 70%respectively,suggesting that the prepared catalysts exhibited good reusability.?2?The supported Pd catalyst of?R?-BINAP?O?-Pd-OMCS were fabricated with the coordination effect of both?R?-BINAP?O?and OMCS.In the asymmetric Heck cross-coupling reaction between phenyl triflate and2,3-dihydrofuran catalyzed by prepared supported catalyst,the reaction conversion was 41.8%,and the enantio-selectivity values ee could reach up to 89.6%,suggesting that the prepared catalyst possessed good catalytic activity and enantio-selectivity.