Aluminum-catalyzed Copolymerization of Cyclic Phosphoesters with Ethylene Oxide
The copolymerization of cyclic phosphoesters(including 2-methoxy-2-oxo-1,3,2-dioxapho-spholane(EMP),2-ethoxy-2-oxo-1,3,2-dioxaphospholane(EEP)and 2-isopropoxy-2-oxo-1,3,2-dioxapho-spholane(IPP))with ethylene oxide(EO)by i-Bu3A1/H3PO4/DBU has been examined.The microstructures,thermal properties and molecular weights of the obtained copolymers were characterized by nuclear magnetic resonance spectroscopy(NMR),gel permeation chromatography(GPC)and differential scanning calorimeter(DSC)and copolymerization kinetics.The copolymerization of EO with EMP,EEP,IPP by i-Bu3Al/H3PO4/DBU has also been successfully achieved at 60 ℃ in 2 h to afford EO-EMP,EO-EEP,EO-IPP copolymers with controllable compositions in high yield by changing the feed ratio.The GPC analysis of copolymers showed that the copolymers possessed high molecular weight(Mn=1.9×104-4.1 × 104)and narrow molecular weight distribution(Mw/Mn=1.83-2.10).The alkoxy substituent group on the phosphorus atom of cyclic phosphoesters did not affect the copolymerization activity of EO with EMP,EEP and IPP,but affected the kinetic behaviours of the copolymerization and the sequence structure of the obtained copolymers.The EO-EMP copolymerization is random copolymerization,while EO-EEP and EO-IPP copolymerization are gradient copolymerization.
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