Preparation And Characterization Of IPN Composite Materials Composed Of Chitosan And Gelatin

The pH-sensitive interpenetrating polymer networks (IPN) films based on chitosan andgelatin using genipin as the cross-linker were prepared and characterized first. The IPN filmswere various compositions and different cross-linking agent content. The structure andmorphology were characterized by means of instrinsic viscosity measurement,Fourier-Transform infrared analyses (FT-IR), scanning electron microscopy (SEM),thermo-gravimetric analysis (TG), and the ninhydrin assays. The physical performance wascharacterized through mechanical properties, water absorption and water retentionperformance and swelling ratio. The instrinsic viscosity measurement suggested the chitosanand gelatin molecules were miscible in the molecular level. Fourier-Transform infraredanalyses, scanning electron microscopy, thermo-gravimetric analysis and results showedthere were strong interactions between chitosan and gelatin molecules. The reactionmechanisms between chitosan or gelatin and genipin examined by FT-IR suggested that thecross-linking of chitosan or gelatin by genipin led to the formation of secondary amide andheterocyclic amino linkage. The scanning electron microscopy suggested in the formation ofgenipin-cross-linked chitosan/gelatin films, cross-linking reaction took place both on chitosanand gelatin, resulting in the formation of IPN. The degree of cross-linking increased withincreasing cross-linking concentration as determined by the ninhydrin assay. Theexperimental values were different from the theoretical values also suggested that some freeamino groups may take part in the interactions between chitosan and gelatin, such asamidization. The tensile strength increased with increasing cross-linking concentration whileelongation at break decreased with increasing cross-linking concentration. The IPN filmswere pH-sensitive, exhibiting reversibility and rapid response in swelling to pH changes. Thecontent of chitosan, cross-linking agent content and pH values had significant effects onswellability.On this basis, the chitosan/gelatin interpenetrating network porous materials wereprepared using freeze-drying method. The adsorption performance of chitosan/gelatin IPN forthe acid orange II dye was studied by the static adsorption experiments. The optimum appliedconditions were also optimized. In addition, the adsorption dynamics was studied and its adsorption type was simulated by the Langmuir and Freundich isothermal equation. Thestatic adsorption experiments showed under the experimental conditions the cross-linkingagent content, pH values, the initial concentration of the dye solution, time andtemperature had a significant effect on adsorption capacity. The negative ΔG values showedthe adsorption performance of chitosan/gelatin IPN for the acid orange II dye wasspontaneously under the experimental condition. The positive values of ΔS implied that therandomness increased. The positive values of ΔH indicated that the adsorption wasendothermic and the process would benefit from the temperature increasing. The isothermmodels revealed that the adsorption process of acid orange II dye onto chitosan/gelatininterpenetrating network porous materials fited well with the Langmuir model whichsuggested the adsorption was monomolecular layer chemisorption. The adsorption kineticsresults indicated that the adsorption kinetics followed the pseudo-second-order model.