Supported neodymium catalysts for MMA polymerization: on the origin of surface-induced stereoselectivity

The polymerization of MMA by a supported neodymium borohydride catalyst proceeds with moderate tendency toward isoselectivity, whereas the molecular precursor generates a syndiotactic-rich polymer. DFT studies reveal that initiation proceeds via borohydride attack on the first coordinated monomer followed by BH3 trapping by the silica surface. The selectivity of the next two insertions was scrutinized, demonstrating that interactions between the growing chain's oxygens and the metal enforce conformations that lead to favoured formation of an isotactic polymer chain.