Hyperbranched Polyether−Polyols Based on Polyglycerol: Polarity Design by Block Copolymerization with Propylene Oxide

Abstract

Multiarm block copolymers were synthesized via anionic ring-opening multibranching polymerization (ROMBP) of glycidol followed by addition of propylene oxide. The resulting polyether−polyols with molecular weights in the range 5000−12 000 g/mol possessed up to five propylene oxide units per end group and showed narrow molecular weight distributions (MWD < 1.7). Via propoxylation the polarity of the highly hydrophilic polyglycerols can be varied, resulting in versatile, highly functional branched polyether polyols. The hyperbranched polyglycerols with oligo(propylene oxide) segments were characterized by 13C and 1H NMR, demonstrating complete propoxylation of all end groups. 1H NMR, SEC, vapor pressure osmometry, and hydroxyl number titration were used to determine molecular weights. The effect of the short poly(propylene oxide) blocks on the flexibility of the polyethers was studied by DSC. The Tg varied between −37 and −71 °C, depending on the length of the propylene oxide segments attached.