Synthesis and characterization of ultra-high molecular weight ethylene-propylene polar elastomers with high functional degree

The synthesis of ultra-high molecular weight (UHMW) ethylene-propylene polar elastomer with high functional degree represents a great challenge. The modification of UHMW ethylene-propylene-ENB terpolymers (EPDM) with high content of 5-ethylidene-2-norbornene (ENB) structural units provides a viable way. The synthesis of UHMW EPDM with high content of ENB structural units is critical for the preparation of UHMW polar EP elastomers with high functional degree. Herein, the copolymerization of ethylene with propylene and the terpolymerization of ethylene, propylene with ENB were investigated using vanadium complex NHC·VOCl3 (PhCH2NCH=CHN(2,4,6-Me3C6H2R)C:VOCl3) were investigated. The UHMW EPDM (Mw = 1059-1586 kg·mol-1) were successfully prepared with high catalytic activity up to 2.65× 105 g polymer·mol-1 of V·h-1. The content of ENB structural units in resulting EPDMs can be increased up to 12.5 mol% (35.4 wt%) by increasing ENB concentration in monomer feed. The epoxidation of UHMW EPDM with m-chloroperbenzoic acid in THF results in an efficient conversion of C=C double bonds in the ENB structural units into epoxy groups. The functionalized EP elastomer containing epoxy groups up to 11.2 mol% has been successfully synthesized. The epoxy groups in the functionalized EP elastomers can be successfully and quantitively converted to carbonyl groups, affording functionalized EP elastomers with high content of norcamphor structural units up to 11.2 mol%. The UHMW EPDM with high content of polar epoxy or carbonyl groups can behave good compatibility with inorganic fillers, which is benefit for the preparation of high-performance composites of UHMW EPDM with inorganic fillers.