Characterization of mPEG–OC and subproducts by using 1H NMR. (a) Oligosaccharide (OC), (b) N-phthaloyl chitosan (NPHOC), (c) mPEG5000, (d) PEG monomethyl ether succinate (mPEG–COOH), (e) PEGylated phthaloyl chitosan (mPEG–NPHOC), (f) PEGylated oligosaccharide (mPEG–OC). (c) and (d) are in D2O, (a) and (f) are in 1% DCl/D2O, (b) and (e) are in DMSO.