Synthesis and properties of O-carboxymethyl chitosan/methoxy poly(ethylene glycol) graft copolymers

O-carboxymethyl chitosan/methoxy poly(ethylene glycol) graft copolymers (OCMCS-g-MPEGs) with different degrees of substitution (DS) were synthesized by reductive N-alkylation of chitosan with poly(ethylene glycol) aldehyde. The properties of OCMCS-g-MPEGs, including the solubility, structure, hydrodynamic behaviors, isoelectric point (IEP) and interaction with water-soluble chitosan, were investigated. As a PEGylated polyampholyte, OCMCS-g-MPEGs can resolve in water over all pH range and the pH value at IEP (pHIEP) decreases when DS increases. The hydrodynamic behaviors of OCMCS-g-MPEGs in deionized H2O are markedly affected by DS and pHIEP in the experiment concentration range. The particle size of the complexes of OCMCS-g-MPEGs with water-soluble chitosan is strongly affected by the concentration of water-soluble chitosan and the pH value.