一種合成聚乙烯亞胺和聚乙二醇之無規共聚物(random copolymer)之方法，包含將溶液中之乙醇胺暴露於電磁輻射下足夠的時間，使乙醇胺聚合(OHCH2 CH2 NH2 )，從而導致形成含有聚乙烯亞胺和聚乙二醇之無規無規共聚物，其中該聚乙烯亞胺包含乙烯亞胺(-CH2 CH2 NH-)單元，且該聚乙二醇包含乙二醇(-CH2 CH2 O-)單元，且該無規無規共聚物中之聚乙烯亞胺具有實質上線性之骨架。A method of synthesizing a random copolymer of polyethyleneimine and polyethylene glycol, comprising exposing ethanolamine in a solution to electromagnetic radiation for a sufficient time to polymerize the ethanolamine (OHCH2 CH2 NH2 ) and thereby resulting in formation of the randome copolymer comprising polyethyleneimine and poly(ethylene glycol), wherein the polyethyleneimine comprises ethyleneimine (-CH2 CH2 NH-) unit and the polyethylene glycol comprises ethylene glycol(-CH2 CH2 O-) unit, and the polyethylenimine of the random copolymer has a substantially linear backbone.