the present invention relates to novel synthetic methods for peg - maleimide derivatives , specifically , novel synthetic methods for peg - maleimide . the final products thereof are useful as a pegylation reagent in the field of bioengineering and the medicinal field or the preparation of medical appliances and by conjugating with certain moieties or specific domains of polysaccharides and biological proteins such as antibodies as a bio - compatible or bio - degradable polymer .