The invention discloses a method for preparing a polypeptide-
polylactic acid-polyethyleneglycol dual-graft
copolymer. The method is characterized in that the molecular weight of a
polypeptide chain segment in the
copolymer is 20000-50000; the molecular weight of a
polylactic acid chain segment is 1000-2000; and the molecular weight of a
polyethylene glycol
chain segment is 500-700. The preparation method comprises the following steps of: 1) synthesizing a polypeptide-
polylactic acid graft
copolymer, namely, adding a polypeptide homopolymer, polylactic acid lauryl
ether, a
solvent and a catalyst to a dry reactor, stirring and reacting for 3-4 days under an
inert atmosphere at 55-58 DEG C, so as to prepare the target in manners of filtering, dialyzing and
drying; and 2) synthesizing the polypeptide-polylactic acid-polyethyleneglycol dual-graft copolymer, namely adding the polypeptide-polylactic acid copolymer, the catalyst, the
solvent and the methoxy
polyethylene glycol to the dry reactor, stirring and reacting for 2-3 days under the
inert atmosphere at 55-59 DEG C, so as to obtain the target in manners of filtering, dialyzing and
drying. The method is simple in process; and the obtained target is a novel biodegradable material.