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

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 H-1 NMR and GPC, the molecular weight M-n 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 H-1 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.