Synthesis And Characterization Of Amphiphilic Grafted Copolymers Modified Chitosan And Their Application

Amphiphilic copolymers consisting of hydrophilic and hydrophobic segments can form nano-size micelle structures with hydrophobic inner core and hydrophilic outer shell in aqueous media.In recent years, Amphiphilic copolymers nanoparticles consisting of hydrophilic and hydrophobic segments have received special attention due to their potential application in many interdisciplinary field. Chitosan has been widely used as an oral delivery system for many bioactive agents due to its nontoxic, biocompatible, and biodegradable characteristics. In addition, polymeric nano-size micelles(10-1000nm) were also considerably more superiority than microcapsule . Based on amphiphilic grafted copolymers mentioned research findings in other fields,in this paper,novel amphiphilic chitosan derivatives were synthesized. The chemical structure and physical properties of copolymers were characterized. And estimate the feasibility of the chitosan derivatives nanoparticles as novel pesticide nanocarriers.Specially, three sections of work were carried as follows:(1) A novel biodegradable amphiphilic copolymer with hydrophobic PLA moiety and a hydrophilic chitosan segment was synthesized by Ring-Opening methods. And hydrophilic CS was attained by the amount of hydrogen peroxide. Then a novel biodegradable amphiphilic copolymer with hydrophobic PLA, DPPE moiety and a hydrophilic chitosan oligomer segment was synthesized. The chemical structures of the copolymers were characterized by FT-IR, NMR (1H NMR, 13C NMR, 31P NMR) and thermogravimetric analysis (TGA).The fluorescence experiments showed that copolymers have a strong tendency to form micelles in aquous medium,with very low critical micelle concentrations (CMC). The dynamic light scattering (DLS) and Transmission electron microscopy (TEM) indicates that the novel biodegradable amphiphilic copolymers dispersed as individual particles with a well-defined spherical shape homogeneously distributed.(2) The imidacloprid-loaded CS-co-PLA copolymer sub-micron particles were prepared by nanoprecipitaion and emulsion/solvent evaporation method. The preliminary investigations for the novel copolymer sub-micron particles have shown that the fabrication method of imidacloprid-loaded sub-micron particles, mass ratio of copolymer to imidacloprid made a great influence on the particle size, size distribution, LC, and imidacloprid release behavior. As the mass ratio of copolymer to imidacloprid increased, the sub-micron particles size and LC decreased. The dynamic light scattering (DLS) and Transmission electron microscopy (TEM) indicates that the imidacloprid-loaded copolymer sub-micron particles dispersed as individual particles with a well-defined spherical shape homogeneously distributed. The imidacloprid-loaded sub-micron particles showed the sustained release process.(3) The chlorpyrifos-loaded CS-co-PLA-DPPE copolymer nanoparticles were prepared by nanoprecipitaion and emulsion/solvent evaporation methods. The preliminary investigations for the novel copolymer nanoparticles have shown that the fabrication method of chlorpyrifos-loaded nanoparticles, mass ratio of copolymer to chlorpyrifos made a great influence on the particle size, size distribution, LC, and chlorpyrifos release behavior. As the mass ratio of copolymer to chlorpyrifos increased, the nanoparticles size and LC decreased. The dynamic light scattering (DLS) and Transmission electron microscopy (TEM) indicates that the chlorpyrifos-loaded copolymer nanoparticles dispersed as individual particles with a well-defined spherical shape homogeneously distributed. The nanoparticles can prolonged pesticide release time due to the amphiphilic structure of the copolymer.