Multistimuli Responsive Supramolecular Cross-Linked Networks On the Basis of the Benzo-21-Crown-7/Secondary Ammonium Salt Recognition Motif

Abstract

A facile route is demonstrated to realize the supramolecular cross-linked networks based on the benzo-21-crown-7/secondary ammonium salt recognition motif, which involves the interchain host–guest interactions between the secondary ammonium salt-functionalized polystyrene and the complementary homoditopic benzo-21-crown-7 cross-linker. Reversible addition–fragmentation chain transfer polymerization is utilized to prepare the well-defined secondary ammonium salt-functionalized graft polymer. As determined by 1H NMR and GPC, the molecular weight Mn is 13.3 kDa with polydispersity value of 1.10, suggesting that 15.9 repeating units of secondary ammonium salt moieties exist in a single polymer chain. The properties of the resulting supramolecular cross-linked networks are characterized in solution by means of 1H NMR titration and viscosity measurements, which indicate the growth of entangled polymer chains after the efficient host–guest complexation. At high concentrations of acetonitrile, the interpenetrating three-dimensional networks could entrap large amounts of solvent and thereby lead to the formation of supramolecular gels, which exhibit multistimuli (thermo-, pH-, and chemo-) responsive sol–gel transition behaviors. Such a strategy will benefit for the further development of intelligent supramolecular materials with desired functionalities.