Controllable Preparation And Application Of Chitin Nanofibers With Different Surface Charged Groups

With the development of nanomaterials and people's deepening awareness of environmental protection,chitin,a renewable natural biopolymer material from fisheries waste resources,has attracted widespread attention in order to cope with the growing energy crisis and resource consumption problems.Oxidation is a common chemical modification method,which can introduce electrostatic repulsion to overcome the hydrogen bond interaction between chitins,thereby obtaining well-dispersed chitin nanomaterials.However,the TEMPO oxidation method commonly used to prepare carboxy chitin nanomaterials can only oxidize?-chitin with a degree of deacetylation less than 1%,which greatly limits the research and application of?-chitin.In this study,we break through the limitations of the previous TEMPO oxidation method for the oxidation of?-chitin and further treat to increase the species of charged functional groups on chitin,realize the controlled preparation of chitin nanofibers with different surface charges using?-chitin from squid pen,and study its applications.The specific work is as follows:In the first part,carboxyl?-chitin nanofibers with diameters of 2-6 nm and lengths of micrometers were successfully prepared from partially deacetylated?-chitin using the TEMPO-NaClO-NaClO₂ oxidation system in the range of 5-30%deacetylation of?-chitin.The effects of the degree of deacetylation of?-chitin in the system,the oxidation time and the amount of NaClO₂ on the oxidation degree were examined.Finally,the special phenomenon of its oxidation of?-chitin was speculated mechanistically.In the second part,squid pen collected from the local seafood market were purified,after deacetylation,TEMPO-NaClO-NaClO₂ oxidation,and secondary deacetylation toobtain zwitterionically charged chitin nanofibers with different surface charges groups.The obtained nanofibers can be well dispersed under acidic and alkaline conditions with diameters of 2-6 nm and lengths in the micron range.The characterization of the effect of different p H on sonication,zeta potential,and thermal properties was also explored.In the third part,the nanomaterials prepared in the previous two parts were used as raw materials and their applications were investigated.The mechanical properties and optical transmittance were investigated by vacuum filtration assisted film formation,and the microscopic morphology was observed.In addition,the emulsification ability of different nanofibers on epoxidized soybean oil was investigated,and it was found that the nanofibers with the presence of amino groups under alkaline conditions had the best emulsification effect.