Journal
MACROMOLECULAR CHEMISTRY AND PHYSICS
Volume 205, Issue 8, Pages 1031-1038Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/macp.200400027
Keywords
block copolymers; germanium initiators; L-lactide; poly(ethylene glycol); ring-opening polymerization
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Spirocyclic initiators were prepared by condensation of Ge(OEt)4 and tetra(ethylene glycol), TEG, or PEG-2000 ((M) over barn = 2000 Da). These spirocycles were used as initiators for the ring-expansion polymerization of L-lactide in chlorobenzene at 120 degreesC. The resulting cyclic block co-polymers were reacted in situ with aliphatic dicarboxylic acid dichlorides (ADADs) or with hexamethylene diisocyanate (HMDI) to achieve chain extension. The reaction conditions were optimized via model reactions. The isolated Ge-free multiblock copolymers were characterized by viscosity and by H-1 NMR measurements. In selected cases SEC measurements and MALDI-TOF mass spectroscopy were conducted. The mass spectra revealed small amounts of cyclic oligo- and polylactides, whereas the high molecular weight multiblock copolymers did not fly.
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