Efficient Polymer Cyclization by Electrostatic Self-Assembly and Covalent Fixation with Telechelic Poly(tetrahydrofuran) Having Cyclic Ammonium Salt Groups

Uniform-size poly(tetrahydrofuran)s (poly(THF)s) having N-phenyl or N-methylpyrrolidinium salt end groups (1p and 1m, respectively) carrying a dicarboxylate counteranion have been prepared as ionic polymer precursors for an intramolecular cyclization reaction. Thus, 4,4‘-biphenyldicarboxylate (2a) was first introduced quantitatively as a counteranion by repeated precipitation of the polymer precursor 1p into an aqueous solution containing dicarboxylate sodium salt. The efficient cyclization was confirmed with the ion-exchange product Ipa having the molecular weight ranging from 4 to 12 kg/mol in diluted THF. The polymer cyclization proceeded effectively also with Ima having N-methylpyrrolidinium salt end groups. There was a pronounced effect upon changing the reaction solvent from THF to chloroform, acetone, toluene, and ethanol. A series of dicarboxylate salts, that is, terephthalate (2b), o-phthalate (2c), succinate (2d), adipate (2e), and trans-2-butene-1,4-dicarboxylate (2f), was then employed for the...