A Challenging Comonomer Pair: Copolymerization of Ethylene Oxide and Glycidyl Methyl Ether to Thermoresponsive Polyethers

Motivated by the oxygen-rich and fully amorphous structure of poly(glycidyl methyl ether) (PGME), a series of thermoresponsive poly(glycidyl methyl ether- co -ethylene oxide) copolymers P(GME- co -EO) with molecular weights in the range of 3000–20 000 g mol –1 were synthesized by the activated monomer polymerization technique. Tetraoctylammonium bromide (NOct 4 Br) was employed as an initiator in combination with triisobutylaluminum ( i -Bu 3 Al) as a catalyst under mild conditions. Polyethers with varying GME content between 31 and 100 mol % were obtained. Triad sequence analysis using 13 C NMR spectroscopy proved that no pronounced block structure was obtained. Differential scanning calorimetry (DSC) revealed that samples exceeding 65 mol % content of GME are amorphous, whereas with lower GME content a low degree of crystallization was observed. Melting temperatures for these polyethers were in the range 9.8–37.5 °C. Furthermore, the copolymers’ lower critical solution temperatures (LCSTs) in aqueous solution were tuned from 55 °C for the PGME homopolymer up to 98 °C by varying the amount of GME. The approach permits to combine two highly biocompatible and water-soluble materials.