Covalent Conversion of Cyclic Onium Salt End Groups of Poly(tetrahydrofuran) by Bulky Counteranions in the Absence and Presence of Macrocyclic Compounds

Abstract

A series of bulky carboxylates was introduced as a counteranion for N-methylpyrrolidinum salt end groups of poly(tetrahydrofuran), poly(THF), having molecular weights of ca. 5000. 4-(7,7,7-Triphenylheptoxy)benzoate was found to remain intact as a counteranion at ambient temperature but to cause the ring-opening reaction of pyrrolidinium groups at 90 °C to produce poly(THF) with bulky stopper groups in a pure form in 71% yield. The relevant ring-opening reaction also took place in the presence of such macrocyclics as 30-crown-10 and cyclodextrins, but an effective entrapping of cyclic components in polyrotaxanes was not achieved presumably because of the entropic repulsion between the two components.