ATRP SYNTHESIS AND SELF-ASSEMBLY BEHAVIOR OF CHITOSAN-O-PMPEGMA
壳聚糖-Ｏ-聚(聚乙二醇甲醚甲基丙烯酸酯)接枝共聚物的ATRP合成及其自组装研究

The bromized sodium dodecyl sulfate(SDS)-chitosan(CS)complex(Br-SCC)was synthesized by conjugating 2-bromo-2-methyl propionic acid to the hydroxyl groups of SCC which was used as an organo-soluble precursor in this study.Br-SCC was used as a macromolecular ATRP initiator to polymerize methyl ether poly(ethylene glycol)methacrylate(PMPEGMA)using copper(I)bromide/bipyridine as a catalyst,yielding SCC-O-PMPEGMA.SDS was removed from the product by precipitating SCC-O-PMPEGMA solution into aqueous tris(hydroxymethyl)amine (Tris) medium.The chemical structure of the intermediate and CS-O-PMPEGMA was studied by FTIR and 1H-NMR.The substitution degree of bromobutyric acid could be modulated by bromobutyric acid/SCC feed ratio.The degree of polymerization of PMPEGMA could be controlled by varying the PMPEGMA/Br-SCC ratio.Complexation behaviors between CS-O-PMPEGMA and heparin were studied by dynamic light scattering,zeta potential analyzer and TEM.With the increase of heparin/CS molar ratio (X),there was an increase in the nanoparticle size and decrease in the zeta potential of the particles.When X was above 2,the size and the zeta potential reached a plateau stage.The ultimate size of the spherical nanoparticles was about 44 nm and the zeta potential was -8.9 mV.CS-O-PMPEGMA which could be conveniently synthesized according to the scheme proposed in this study has well-defined chemical structure.The grafting of PMPEGMA has no effect on the cationic density of the final product.In addition,the copolymers could form spherical micelles with anionic agents.The above characteristics of CS-O-PMPEGMA make it promising for tumor targeting and gene delivery.