Synthesis of amphiphilic macrocyclic graft copolymer consisting of a poly(ethylene oxide) ring and multi-poly(ε-caprolactone) lateral chains

A series of amphiphilic macrocyclic graft copolymers composed of a hydrophilic poly(ethylene oxide) as ring and hydrophobic poly(epsilon-caprolactone) as lateral chains with different grafting lengths and densities of side chains were prepared by a combination of anionic ring-opening polymerization and coordination-insertion ring-opening polymerization. The anionic ring-opening copolymerization of ethylene oxide (EO) and ethoxyethyl glycidyl ether (EEGE) was carried out first using triethylene glycol and diphenylmethyl potassium (DPMK) as co-initiators, and a linear alpha,omega-dihydroxyl poly(ethylene oxide) with pendant protected hydroxymethyls (l-poly(EO-co-EEGE)) was obtained. The monomer reactivity ratios of these compounds are r(1(EO)) = 1.20 +/- 0.01 and r(2(FEGE)) = 0.76 +/- 0.02, respectively. Then the ring closure of l-poly(EO-co-EEGE) was achieved via ail ether linkage by reaction with tosyl chloride (TsCl) in the presence of solid KOH. The crude cyclized product containing the linear chain-extended polymer was hydrolyzed in acidic conditions first and then purified by treating with alpha-CD. The pure cyclic copolymer of EO and glycidol (Gly) with multipendant hydroxymethyls [c-poly(EO-co-Gly)] as the macroinitiator was used further to initiate the ring-opening polymerization of epsilon-caprolactone (CL), and a series of amphiphilic macrocyclic graft copolymers c-PEO-g-PCL were obtained. The final products and intermediates were characterized by GPC, NMR and MALDI-TOF in detail. (C) 2008 Elsevier Ltd. All rights reserved.