The Preparation and Chemistry of Dicationically Active Polymers of Tetrahydrofuran

Abstract

The anhydrides of the very strong acids, CF ₃ SO ₃ H and FSO ₃ H, polymerize tetrahydrofuran (THF) to give a living polyether having cationic activity at each chain end. The surprising fact that both chain ends are cationically active necessitates the postulation of a reaction mechanism wherein the YSO,-ester end group (Y=CF ₃ or F) formed as an intermediate in the polymerization generates an oxonium ion by a subsequent O-alkylation reaction involving either a THF molecule or a nearest neighbor ether group of the polymer chain. Kinetic studies of polymerizations involving (CF, SO,) ₂ 0 and the bis-ester, CF ₃ SO ₃ —C ₄ H ₅ —O ₃ SCF ₃ , as initiators indicate that chain growth is much faster where an oxonium ion rather than an ester is the end group. The chemistry of poly-THF dications is discussed. These are strong alkylating agents which make possible the facile preparation of unusual copolymers, block copolymers, and functionally terminated polymers.