Counter Cation Dependent and Stimuli Responsive Supramolecular Polymers Constructed by Calix[4]pyrrole Based Host–Guest Interactions

Abstract

Carboxylate tethered calix[4]pyrroles in the form of their tetrabutylammonium (TBA) and cetyltrimethylammonium (CTA) salts were synthesized via an acid base reaction between the corresponding carboxylic acid functionalized calix[4]pyrrole and tetrabutyl‐ or cetyltrimethylammonium hydroxide. The host–guest recognition motif based on these calix[4]pyrrole macrocycles and tethered carboxylate units was employed to construct novel A–B type supramolecular polymers from low molecular weight monomers in chloroform. These supramolecular polymers were found to be dependent on the counter cation in terms of the properties of supramolecular polymers. 1H‐, DOSY‐, NOESY‐NMR spectroscopic analyses, viscosity measurements, and SEM results were used to characterize supramolecular polymers and revealed that the CTA cation becomes a direct part of supramolecular polymer via cation–π interactions between the ammonium part of CTA and carboxylate‐bound calix[4]pyrrole, effecting the overall properties of supramolecular polymers such as viscosity, gel formation, and drawing fibers. Additionally, reversible pH‐ and thermo‐responsiveness of the supramolecular polymers were demonstrated for the first time for an anion recognition induced calix[4]pyrrole based supramolecular polymer.

Ion Pair Recognition Based Supramolecular Polymer Showing Rapid and Reversible Sol–Gel Transition through van der Waals Interactions

“…As 3 can form linear supramolecular polymers through host–guest complexation between calix[4]­pyrroles and tethered carboxylate units, the degree of polymerization (DP ≈ ( K a C ) 1/2 ) could be estimated using the isodesmic model based on the affinity constant between the model system 1 and acetate anion (as CTA salt). The binding constant was determined to be K a = 2.1 × 10 3 M –1 in CHCl 3 (Figures S9 and S10), which is stronger than the corresponding tetrabutylammonium guest . Using this binding constant, the average number of monomers in the supramolecular polymer was estimated to be approximately 30 for 3 at a concentration of 0.51 M in CHCl 3 .…”

“…The binding constant was determined to be K a = 2.1 × 10 3 M −1 in CHCl 3 (Figures S9 and S10), which is stronger than the corresponding tetrabutylammonium guest. 28 Using this binding constant, the average number of monomers in the supramolecular polymer was estimated to be approximately 30 for 3 at a concentration of 0.51 M in CHCl 3 . The estimated DP in this manner corresponds to a ∼24 kDa number-average molecular weight.…”

Multiresponsive, Self-Healing, and Hierarchical Materials Constructed from Anion Recognition-Based Supramolecular Polymer Networks

“…Octamethylcalix[4]­pyrrole ( CP in Scheme ) is a tetrapyrrolic macrocycle that can bind anions selectively in organic media through hydrogen bonding between pyrrole NHs and anions. Among the various anions, one of the anions that CP can bind strongly is acetate (in the form of its tetrabutylammonium salt, K a = 3.5 × 10 5 and 1.65 × 10 3 M –1 in CH 3 CN and CHCl 3 , respectively). , Therefore, various supramolecular polymers based on the carboxylate recognition ability of calix[4]­pyrroles have been reported using homo- or heteroditopic host architectures − with the aid of different interaction types, such as host–guest, ion-pair recognition, and orthogonal self-assembly …”

An AB2‐Type Hyperbranched Supramolecular Polymer Based on Calix[4]Pyrrole Anion Recognition: Construction, Stimuli‐Responsiveness, and Morphology Tuning

“…[27][28][29][30][31][32][33][34][35][36] They were also used in the preparation of linear supramolecular polymers with AB and AABB type topologies in which host-guest, ion-pair and orthogonal interactions play critical roles. [8,[37][38][39][40] These advancements prompted us to design an easy-toprepare, highly organic soluble heterotropic calix [4]pyrrole monomer bearing two negatively charged domains that can be strongly bound to the hydrogen bonding array of calix [4]pyrrole. In return, we would be able to create a synthetic, self-assembled SHP based on anion recognition ability of calix [4]pyrrole skeleton.…”