Covalent conversion of cyclic onium salt end groups of poly(tetrahydrofuran) by bulky counteranions in the absence and presence of macrocyclic compounds

A series of bulky carboxylates was introduced as a counteranion for N-methy lpyrrolidinum salt end groups of poly(tetrahydrofuran), poly(THF), having m olecular 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 degrees C to produce po ly(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 co mponents in polyrotaxanes was not achieved presumably because of the entrop ic repulsion between the two components.