Fast access to dendrimer-like poly(ethylene oxide)s through anionic ring-opening polymerization of ethylene oxide and use of nonprotected glycidol as branching agent

Dendrimer-like poly(ethylene oxide)s (PEOs) were synthesized through a semicontinuous process based on the anionic ring-opening polymerization (AROP) of ethylene oxide (EO), followed by AROP of a mixture of glycidol (G) and propylene oxide (PO). Glycidol was used as branching agent generating two hydroxyl groups after ring-opening, whereas propylene oxide served to prevent the aggregation of the generated terminal alkoxides. A three-armed PEO star was first prepared through AROP of EO from 1,1,1-tris(hydroxymethyl)ethane as trifunctional precursor using dimethyl sulfoxide (DMSO) as solvent. After completion of EO polymerization and without isolating the PEO star precursor, G and PO (molar ratio 1:3) were added in the same batch to be polymerized either sequentially or randomly. This led to a three-armed PEO star with an average number of terminal hydroxyls per arm which depended on the number of G units inserted at PEO chain ends, as determined by 1H NMR spectroscopy. Growth of the second and the third generation of PEO could be achieved upon reiterating the same steps of AROP of EO and subsequent AROP of G and PO (arborization step) in one pot, affording dendrimer-like PEOs of generation 3 with moderately distributed but expected molar masses. In a variant of this strategy, G was copolymerized in the presence of allyl glycidyl ether during the arborization step in order to introduce allylic double bonds at the branching points of the dendrimer-like PEOs. © 2009 American Chemical Society.