A highly crosslinked hyperbranched polymer that rapidly swells and shrinks in a halogenated solvent in response to the addition of an acid or base has been prepared by Cu(I) catalysis of the reaction between a diazide and an amine-containing trialkyne. The triazole linkages in the polymer are highly stable and may also play a role in the swelling behavior. The swelling-deswelling process is reversible. (c) 2006 Wiley Periodicals, Inc.