Study of Anionic Ring-Opening Polymerization and Macromolecular Structure Characterization for Poly(ethylene oxide)-poly(tetrahydrofuran)-poly(ethylene oxide) Triblock Copolymer

摘要

A triblock copolymer with narrow molecular weight distribution (Mw/Mn < 1.2), poly(ethylene oxide)-poly(tetrahydrofuran)-poly(ethylene oxide), was synthesized by anionic ring-opening polymerization of ethylene oxide using alkoxide as a macroinitiator which was prepared by reacting hydroxyl-terminated poly(tetrahydrofuran) with NaH. The copolymer's structure was characterized by FTIR, ~1H NMR and ~(13)C NMR and well confirmed with its original structure design. The block copolymer's molecular weight and polydispersity as well as the crystalline behaviour were measured and analyzed by size exclusion chromatography/multi-angle laser light scattering (SEC/MALLS) and differential scanning calorimeter. The detailed synthesis conditions and possible polymerization mechanism including terriperature, pressurre and time on ring-opening polymerization were systematically explored. The results demonstrated that in order to obtain a well defined block structure with narrow molecular weight distribution, the optimum synthesis process was determined as the use of solution polymerization under the pressure of 200 psi at 70 °C for 8 h. It was also found that block copolymer's crystalline behaviour changes with lecular weight.