New Sn(IV) and Ti(IV) bis(trimethylsilyl)amides in D,L-lactide polymerization, SEM characterization of polymers

Ring-opening polymerization of D,L-lactide initiated with new chlorotris(bis(trimethylsilyl) amido) tin(IV), tetrakis(bis(trimethylsilyl)amido) tin(IV) and titanium(IV) was investigated. New complexes reveal practically quantitative conversion degrees and produced polymers with higher molecular weight with respect to reference alkoxo-species. The X-ray crystal structure of chlorotris(bis(trimethylsilyl)amido) tin (IV) was investigated. Axial enantiomerism of [SnCl{N(SiMe(3))(2)}(3)] molecules in solution was studied by high-field dynamic NMR, the value of Gibbs activation energy Delta G(double dagger) = 59.5 kJ/mol. Field emission SEM investigation of bulk polymer samples and thin films on conductive AI foil revealed a stratified fibrous textures in the bulk polymers, as well as nanoscaled topographical features due to coils and entanglements of individual macromolecules in thin films. (C) 2008 Elsevier Ltd. All rights reserved.