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 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 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.

Stepwise Unfolding of Single‐Chain Nanoparticles by Chemically Triggered Gates

“…As noted, the dissociation of the hydrogen-bonding system can be induced by addition of acompetitive solvent such as methanol, [34] while the host-guest interaction can be disrupted by adding asimple potassium salt as the potassium cation is complexed stronger by B21C7 than the AS moiety. [33] Theu nfolding of the dual folding system in P16 can be realized by first breaking the hydrogen bonds of HW/CAa nd subsequently the B21C7-AS interaction or vice versa (pathway independ- Table 2.…”

“…The DLS-derived hydrodynamic diameters (D h ,s ee Figure 2a,b) of the folded and unfolded polymers P6 and P16 are listed in Table 2. [33] Theu nfolding of the dual folding system in P16 can be realized by first breaking the hydrogen bonds of HW/CAa nd subsequently the B21C7-AS interaction or vice versa (pathway independ- Table 2. [33] Theu nfolding of the dual folding system in P16 can be realized by first breaking the hydrogen bonds of HW/CAa nd subsequently the B21C7-AS interaction or vice versa (pathway independ- Table 2.…”

Glycoluril Clips for the Construction of Chemoresponsive Supramolecular Polymer Networks through Homodimer Cross‐Links

“…The majority of so far reported supramolecular networks are thermoresponsive. The diversity of known supramolecular motifs enables the design of materials giving a response in a wide temperature range, suitable for a particular application . In case of biological systems, which are usually isothermic, materials that would respond to a certain chemical signal are desired.…”

“…[12] Depending on the applied supramolecular motif, the formed network exhibits stimuliresponsiveness against a particular factor, such as temperature, [2] pH, [13] chemical agent, [8] etc. Moreover, some systems display multi-responsiveness, i. e., sensitivity against two or more factors, for example temperature and a certain chemical factor, [5][6]14] which substantially widens the range of such materials applications.…”

“…The diversity of known supramolecular motifs enables the design of materials giving a response in a wide temperature range, suitable for a particular application. [2,6] In case of biological systems, which are usually isothermic, materials that would respond to a certain chemical signal are desired. The extent of chemoresponsiveness of supramolecular networks, however, seems to be limited, since most of reported systems are usually sensitive to pH change or the presence of inorganic cations [15][16] /anions.…”