Tri-block copolymers of polyethylene glycol and hyperbranched poly-3-ethyl-3-(hydroxymethyl)oxetane through cationic ring opening polymerization
2009
Rahm, Martin | Westlund, Robert | Eldsäter, Carina | Malmström, Eva
Tri-block copolymers of linear poly(ethylene glycol) (PEG) and hyperbranched poly-3-ethyl-3-(hydroxymethyl)oxetane (poly-TMPO) are reported. The novel dumb-bell shaped polyethers were synthesized in bulk with cationic ringopening polymerization utilizing BF₃OEt₂ as initiator, via drop-wise addition of the oxetane monomer. The thermal properties of the materials were successfully tuned by varying the amount of poly-TMPO attached to the PEG-chains, ranging from a melting point of 54 °C and a degree of crystallinity of 76% for pure PEG, to a melting point of 35 °C and a degree of crystallinity of 12% for the polyether copolymer having an average of 14 TMPO units per PEG chain. The materials are of relatively low polydispersity, with Mn/Mw ranging from 1.2 to 1.4. The materials have been evaluated for usage with the energetic oxidizer ammonium dinitramide.
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