Study On Structure And Properties Of Desmartine Oxidized Starch

In this paper,taking Dess-Martin as the oxidant and corn starch and maltose as the reaction main material,in order to study the effect of Dess-Martin oxidant on the single base of corn starch,maltose with small molecular weight and similar link structure was selected for oxidation,and its structure was analyzed.Due to the good film-forming and mechanical properties of Dess-Martin oxidized starch,the oxidized starch was plasticized to prepare thermoplastic oxidized starch,and the surface morphology,structure and properties of thermoplastic oxidized starch were studied.Further blending oxidized starch with PBAT and preparing a film to study the structure and properties of oxidized starch-based biodegradable membranes.The results of XRD and SEM showed that the surface of oxidized maltose particles showed irregular state,and its molecular morphology changed from amorphous state to crystalline structure.TG curve showed that the thermal stability of maltose decreased to a certain extent after oxidation.FT-IR and XPS spectra showed that carbonyl group and carbon-carbon double bond existed in oxidized maltose.Three kinds of oxidation of maltose can be determined by combining the results of 13C-NMR and 1H-NMR and HRMS.In the first,hydroxyl at C1 is oxidized to carboxyl,whose molecular formula is C₁₂H₂₂O₁₁.In the second one,hydroxyl at C2 is oxidized to carbonyl group.Due to the instability of?-hydroxyl ketone,dehydration at C3 and C4 leads to the formation of double bonds,whose molecular formula is C₁₂H₁₈O₁₀.The third one oxidizes hydroxyl groups at C1 and C2,and its molecular formula is C₁₂H₁₈O₁₀.Starch is a polymer compound with a small number of end groups,which is different from maltose.When starch is oxidized,Desmartine oxidant mainly acts on hydroxyl groups at C2 and C6,oxidizing hydroxyl groups at C2 into ketone carbonyl group and hydroxyl groups at C6 into aldehyde group.The instability of?-hydroxyl ketone after oxidation results in dehydration of C3 and C4 to form carbon-carbon double bonds.Taking corn starch,gelatinized oxidized starch,esterified starch and oxidized esterified starch as contrast samples,the structure,properties and surface morphology of oxidized starch after plasticizing were studied.The results are as follows:The mechanical test results showed that the tensile strength of the modified starch increased from 9.27 MPA to 11.41MPA.XRD Patterns showed that the crystalline structure of plasticized starch was destroyed and the crystallinity decreased.DSC curves showed that the glass transition temperature of oxidized starch was the lowest after plasticizing.The results of contact angle test showed that the oxidized starch was more hydrophilic.After blending oxidized starch with PBAT,the contact angle increased from 55.51°to 94.64°.The disadvantage that oxidized starch is more hydrophilic is also improved.