Uniform size poly(THF)s having N-phenylpyrrolidinium salt as a single and both end groups (1 and 2) were synthesized as a reactive precursor to produce star polymers, polymacromonomers, and model networks through the "electrostatic self-assembly and covalent fixation" technique. The N-phenylpyrrolidinium salt group was found to undergo a ring-opening reaction exclusively by a series of carboxylate counteranions at an appropriately elevated temperature, in contrast to the case of the N-methylpyrrolidinium salt group, which caused a concurrent demethylation by a nucleophilic attack of carboxylate anions on the N-methyl group. In particular, even a weak nucleophile such as p-nitrobenzoate counteranion was able to cause a quantitative ring-opening reaction at 80 degrees C, in contrast to the unreactive N-methylpyrrolidinium salt group at the same conditions. The improved selectivity as well as reactivity in the ring-opening reaction of N-phenylpyrrolidinium salt group allowed one to utilize 1 and 2 to produce effectively covalently linked star polymers, polymacromonomers, and model networks, first by the isolation of the ionically linked polymer assemblies formed through the ion-exchange reaction of either 1 or 2 with polycarboxylate salts and the subsequent heat treatment of them.