Silica-Grafted Neodymium Catalysts for the Production of Ultrahigh-Molecular-Weight cis-1,4-Polyisoprene

Abstract

Supported neodymium-based Ziegler-type catalysts are obtained by grafting homoleptic methylaluminate Nd(AlMe4)3 onto high-surface silica materials including periodic mesoporous silicas MCM-41, SBA-15, and KIT-6. Low [Et2AlCl]-cocatalyst contents allow for the fabrication of polyisoprenes with ultrahigh molecular weight (UHMWPI). The synthetic rubbers display molecular weights as high as 3×106 g mol−1, polydispersity indices as low as 1.2, and microstructures with 99 % cis-stereospecificity. Combined analysis of the organolanthanide/silica hybrid materials by nitrogen physisorption, FTIR and magic angle spinning NMR spectroscopies, and elemental (metal) analysis assist in elucidating the intrapore surface organometallic chemistry and suggest the formation of unprecedented organolanthanide species.