Synthesis and Characterization of Polyhedral Oligomeric Silsequioxane-Core Star Polystyrene via Nitroxide-Mediated Polymerization
Résumé
Multifunctional NMP initiator with a core of cubic silsesquioxane (POSS) was synthesized starting from the coupling of Octa(3-aminopropyl)octasilsesquioxane with 2-Methyl-2-[N-tert-butyl-N-(1-diethoxyphosphoryl-2,2-dimethylpropyl)aminoxy]-N propionyloxysuccinimide. The obtained POSS-based multialkoxyamine was then used as NMP initiator for the polymerization of styrene leading to the formation of star polystyrenes of narrow dispersity with a core consisting of dispersed nanosized hard particles. We demonstrated that stars with a predetermined molecular weight and a control of dispersity could be synthesized by simply controlling reaction parameters and restricting the monomer conversion typically below 30 - 35%. The precise structure of POSS based star polystyrenes was analyzed by the characterization of the individual arms obtained after etching the Si-O-Si bonds of the core. The influence of POSS core on the glass transition temperature of nanocomposites was investigated and compared to that of their cleaved products using differential scanning calorimetry.