Synthesis of hyperbranched polymers by the anionic ring-opening polymerization of 3,3-bis(hydroxymethyl)oxetane

The anionic ring-opening polymerization of 3,3-bis(hydroxymethyl)oxetane (BHO) was carried out using t-BuOK as an initiator in the presence of 18-crown-6-ether (18-C-6) in NMP at 180 degreesC, affording the corresponding hyperbranched polyethers, poly(BHO)s containing an oxetanyl group and many hydroxyl groups at the ends in 83-98% yields. Since the resulting poly(BHO)s were insoluble in common organic solvents, the poly(BHO)s were treated with acetic anhydride to obtain poly(BHO-Ac)s containing acetyl groups at the ends. The M,,s and degree of branching (DB) of poly(BHO-Ac)s were in the range of 2600-4400 estimated by SEC and 0.09-0.55 calculated by C-13 NMR spectroscopy, respectively. The cationic copolymerization of poly(BHO-Ac) and 3-ethyl-3-phenoxymethyloxetane (EPO) was examined using BF3OEt2 as an initiator in CHCl3 at 0 degreesC for 24 h, affording pseudo dendritic polymers, poly[poly(BHO-Ac)/EPO]s with M-n = 11000-15000 in 58-65% yields. Furthermore, the obtained poly[poly(BHO-Ac)/ EPO] was hydrolyzed with KOH to afford the poly[poly(BHO)/EPO] containing many hydroxyl groups.