Preparation And Characterization Of PEG-Based Amphiphilic Copolymers By Oxyanion-initiated Polymerization

Methoxy poly(ethylene glycol)-b-poly(ethyl cyanoacrylate) (mPEG-b-PECA), and poly(ethyl cyanoacrylate)-b-poly(ethylene glycol)-b-poly(ethyl cyanoacryla) (PECA-b-PEG-b-PECA) were synthesized via oxyanion-initiated polymerization from PEG or mPEG as initiators. The amphiphilic block copolymers were characterized by GPC, 1H-NMR, FTIR. The results indicate that the molecular mass is well controlled with low polydispersities. Fluorescent polymer (mPEG-b-PECA-CZ) was also synthesized by oxyanion-initiated polymerization, their fluorescent property was analyzed. PEG/PECA nanoparticles were prepared by the nanoprecipitation technology. The results of laser particle size analyzer (LPSA) and transmission electron microscopy (TEM) show that the nanoparticles are of spherical morphology with the size of nanoparticles less than 100 nm. Using dexamethasone as model drug, the drug loading ability of amphiphilic block copolymers and fluorescent-labeled block polymer was studied. The results show that dexamethasone can be effectively incorporated into PEG/PECA copolymer nanoparticles. Any initial burst release was not observered in the in vitro release of all the samples. The release rate and accumulated release amount of dexamethasone increase upon increasing the molecular weight of the hydrophobic chain in the copolymers.mPEG macroinitiators were first prepared from mPEG and KH. Amphiphilic block copolymers (mPEG-b-PDLLA-b-PDMAEMA) were synthesized by oxyanion-initiated polymerization using DLLA, DMAEMA as monomers. The resutlts of GPC, FTIR, 1H-NMR indicate that the copolymerization is well controlled with low polydispersities. The block copolymers dissolved in aqueous solution, on addition of poly (acrylic acid) (PAA), micellization occurred to form complex nanoparticles comprising PDLLA core, polyelectrolyte complex middle layer and PEG shell. The size of complex nanoparticles measured by LPSA is less than 300 nm and depends on the molar ratio between the oppositely charged subunits (DMAEMA to AA).