Macromolecular Chemistry and Physics

Poly(lactides) with controlled molecular architecture initiated from hydroxyl functional dendrimers and the effect on the hydrodynamic volume

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Star poly(lactides) with well defined molecular architectures have been synthesized from multifunctional dendritic initiators derived from 2,2′-bis(hydroxymethyl)propionic acid (bis-MPA) derivatives. The bis-MPA derivatives, in the presence of stannous 2-ethylhexanoate, generated new polymeric structures with accurate control of molecular weight and narrow molecular weight distributions (<1.1). The combination of 1H NMR and 13C NMR spectroscopy, and size exclusion chromatography (SEC) showed that all polymers have the requisite structure and the correct number of arms. This allowed characterization of the hydrodynamic volume as a function of molecular weight and number of arms. The results showed a linear relationship of the hydrodynamic volume as a function of the molecular weight for the polymers having two, four and six arms. However, the star polymers with twelve arms showed a relatively much smaller hydrodynamic volume, suggesting that these macromolecules are more globular in their shape. The same effect was found for star poly(ε-caprolactone)s. © Wiley-VCH Verlag GmbH, 1999.