writer：Guangwen Cheng, Xiaodong Fan,. Wei Tian, Yuyang Liu and Jie Kong
keywords：controlled anionic polymerization, ‘click’ chemistry,three-arm poly(ethylene glycol),synthesis
source：期刊
specific source：Polym Int 2010; 59: 543–551
Issue time：2009年

Poly(ethylene glycol) (PEG) is an important water-soluble polymer, which is widely used in the biomedical field because
of its good biodegradability, biocompatibility and permeability. It is usually synthesized by anionic polymerization of
ethylene oxide but side reactions lead to the formation of some oligomers. High molecular weight PEG can be obtained,
however, through coordinated anionic polymerization. Recently a novel controlled anionic polymerization based on the
initiating system ammonium bromide/trialkylaluminium was reported. Related studies have shown that the controlled anionic
polymerization allows the synthesis of linear polyethers with low dispersity in a wide range of molecular weights at ambient
temperature. Unfortunately, so far this controlled anionic polymerization has not been used to synthesize polymers with
complex architectures. In the work reported here, controlled anionic polymerization was combined with ‘click’ chemistry
for the first time to synthesize polyethers with multiple arms. Firstly, controlled anionic polymerization was employed
to synthesize a linear bromine-terminated PEG (PEG-Br) using ethylene oxide as the monomer and tetraoctylammonium
bromide/triisobutylaluminium as the initiating system at room temperature. The terminal bromine in the PEG thus synthesized
was then converted into an azide group by the reaction of PEG-Br and sodium azide. A trifunctional linking agent was also
preparedbythereactionoftrimethylolpropaneandpropiolicacid.Byusing‘click’chemistry,athree-armPEGwasfinallyobtained
through the reaction of the azide-terminated PEG and the trifunctional linking agent. The chemical structure of the polymer
thus synthesizedwas characterizedusing infrared spectroscopy,NMRspectroscopy,matrix-assisted laser desorption/ionization
time-of-flightmassspectrometryandsize-exclusionchromatographywithmulti-anglelaserlight scattering. Itwasfoundthatthe
synthesizedpolyether possesses thedesignedstructure. Considering thewideapplicabilityof controlledanionic polymerization
and ‘click’ chemistry, their combination is a valuable way to synthesize various polyethers withmultiple arms.