Synthesis And Applications Of New Amphiphilic Diblock Copolymers

In this thesis, a series of novel amphiphilic copolymers were developed which contain polylactic acid as hydrophobic unit and polyethylene glycol (PEG) as hydrophilic unit. The diblock copolymers were formed by linking unit in which there are two disulfide bonds and two hydrogen bonds. Their chemical structures and molecular weights for these copolymers were characterized by NMR, IR and GPC.Firstly polyethylene glycol with mono methyl ether reacted with the sequence specific H-bonded linking units, the other part of the H-bonded linking units contains hydrophobic polylactic acid was synthesised at the same time. All of their structures were characterized by NMR, IR and GPC.Secondly the amphiphilic diblock copolymers were synthesised by the linking unit in the presence of iodine in solution. Their chemical structures were characterized by FT-IR and 'H-NMR. The molecular weight and the molecular distribution was characterized by GPC The Mn of M1 is 1660 and its polydispersity index (PDI) is 1.20; the Mn of M2 is 2140 and its polydispersity index (PDI) is 1.13; the Mn of M3 is 2470 and its polydispersity index (PDI) is 1.29;and the Mn of M4 is 10200 and its polydispersity index (PDI) is 1.42.The solubility experiments for these amphiphilic diblock copolymers demonstrated they are easily dissolved in chloroform, methylene chloride, THF, ethyl acetate and acetone. But they are poorly dissolved in methanol and ethanol. All of the primary exploration sugguests the new kind of diblock copolymers is potential in drug delivery. Further research in self assembled nanocarriers based on these diblock copolymers is underway.