Synthesis of Poly(Ethyl vinyl ether) with high molecular weight by rare-earth metal cationic catalysts

Abstract

Ethyl vinyl ether (EVE) polymerizations by rare-earth metal complexes were studied. The metallocene complexes 1–3 activated by organoborate displayed extremely high catalytic activities (≤1.50 × 106 g mol−1 h−1) for EVE polymerization at 25 °C. The non-metallocene complexes 4–6 were nearly inert under the same conditions. The resultant molecular weights produced by 1/[Ph3C][B(C6F5)4] increased from 2.98 × 104 to 19.3 × 104 g mol−1 with the temperature declining from 0 to −45 °C and the addition of 10 equivalents of AliBu3 to the binary system 1/[Ph3C][B(C6F5)4] resulted in the higher molecular weight product (32.5 × 104 g mol−1) at −45 °C. With the molar ratio of EVE-to-1 increased from 2000:1 to 10000:1, the resultant molecular weight reached 107.3 × 104 g mol−1 but the catalytic activity dropped dramatically from 7.60 × 105 to 0.57 × 105 g molSc−1 h−1. The dicationic species formed by the reaction of 1 with 2 equivalents of [Ph3C][B(C6F5)4] displayed high catalytic activity for EVE polymerization and gave high molecular weight product in the presence of AliBu3.