The Preparation And Performance Of Water Suspension Nanocapsules Of Alginate Hydrophobic Dericatives

Alginate is a natural water-soluble linear polysaccharide. In this study, the nanocapsule featured with stablity, delayed release, water solution, decentralized and encapsulation was prepared by the hydrophobic modified amphiphilic polymer surfactant and based on microemulsion template.First of all, hydrophobic Octyl-grafted alginate-amide derivative was synthesized by the amidation of alginate and octylamine. It was confirmed by FTIR,1H NMR and elemental analyzer. Then we analyzed the variation of the surface tension with change of concentration of octyl-grafted alginate-amide derivative. Furthermore, we studied the effects of different substitution degrees and pH values on octyl-grafted alginate-amide derivative concentrations. The results indicated that hydrophobic alginate derivative was amphiphilic, the surface tension decreased with hydrophobic modification and the critical aggregation concentration was decreased with the increased of degree of substitution and pH value of the solution.Two kinds of λ-cyhalothrin water suspended nanocapsules were prepared by microemulsion as template and Octyl-grafted alginate-amide derivative as shell material. The methods (internal curing method and external curing method) were distinguished by the locations of calcium. External curing method was described in details as following:microemulsion was formed by diffusion of the LCH molecule into the hydrophobic microdomain of self-aggregates process of nonionic surfactant; then numerous hydrophobical modified alginate derivatives gathered at the surfaces of the microemulsion droplets; finally, shell was formed by the inward association of OAD with Ca2+. Internal curing method was described as following:microemulsion was formed by compounding of nonionic surfactant and anionic surfactant calcium dodecylbenzenesulfonate; the multi-core nanocapsule was formed by the association of OAD with Ca2+which is gathering at the surfaces of the microemulsion after addition of the Octyl-grafted alginate-amide derivative.The morphology of nanocapsules was characterized by transmission electron microscopy; the sizes and stability of nanocapsules was characterized by laser particle size analysis and the effects of different octyl-grafted alginate-amide derivatives, calcium chloride and the amount of surfactant on the sizes of nanocapsules were discussed with the analysis of capsule particle sizes by laser particle size analyzer; moreover, the release performance of the nanocapsules was studied by the release quantity of λ-cyhalothrin determined by gas chromatography. The results indicated: the size of nanocapsules decreased with the increase of surfactant content; The average size of water suspension nanocapsules with external curing method was7.76nm and it was198.01nm with internal curing method; The nanocapsule has a high loading efficiency valve of99.95%and loading capacity was11.16%with internal curing method, It has a loading efficiency valve of90.56%and loading capacity was15.82%with internal curing method. The average sizes of microemulsion(A) and nanocapsules(B) has a tiny variations with storage time passed. Compared the release profiles of microemulsion, the nanocapsules restrained the release of λ-cyhalothrin.