A Dual-Responsive Supra-Amphiphilic Polypseudorotaxane Constructed from a Water-Soluble Pillar[7]arene and an Azobenzene-Containing Random Copolymer

Macromolecular supra-amphiphiles refer to a kind of macromolecular amphiphiles whose hydrophlic and hydrophobic parts are connected by noncovalent forces. They have applications in various fields, such as drug delivery, sensor systems, and biomedical materials. Here we report a novel molecular recognition motif between a new thermoresponsive water-soluble pillar[7]­arene (<b>WP7</b>) and an azobenzene derivative. Furthermore, we utilized this recognition motif to construct the first pillararene-based supra-amphiphilic polypseudorotaxane which can self-assemble to form vesicles in water. Due to the dual-responsiveness of the molecular recognition motif (the thermoresponsiveness of <b>WP7</b> and photoresponsiveness of azobenzene), the reversible transformations between solid nanospheres based on the self-assembly of the polymer backbone and vesicles based on the self-assembly of the supra-amphiphilic polypseudorotaxane were achieved by adjusting the solution temperature or UV–visible light irradiation. These dual-responsive aggregation behaviors were further used in the controlled release of water-soluble dye calcein molecules

Redox-Responsive Complexation between a Pillar[5]arene with Mono(ethylene oxide) Substituents and Paraquat

Host–guest complexation between a pillar[5]arene with mono(ethylene oxide) substituents and paraquat was studied. We demonstrated that this pillar[5]arene can form a 1:1 complex with paraquat in solution and in the solid state. The formation of this complex was confirmed by proton NMR spectroscopy, electrospray ionization mass spectrometry, and single crystal X-ray analysis. Furthermore, this complexation can be reversibly controlled through the sequential addition and removal of Zn powder. The host substituent effect on the complexation ability was also addressed

Redox-Responsive Complexation between a Pillar[5]arene with Mono(ethylene oxide) Substituents and Paraquat

Host–guest complexation between a pillar[5]arene with mono(ethylene oxide) substituents and paraquat was studied. We demonstrated that this pillar[5]arene can form a 1:1 complex with paraquat in solution and in the solid state. The formation of this complex was confirmed by proton NMR spectroscopy, electrospray ionization mass spectrometry, and single crystal X-ray analysis. Furthermore, this complexation can be reversibly controlled through the sequential addition and removal of Zn powder. The host substituent effect on the complexation ability was also addressed

pH-Responsive Supramolecular Control of Polymer Thermoresponsive Behavior by Pillararene-Based Host–Guest Interactions

We demonstrate precise control of the lower critical solution temperature (LCST) behavior of a thermoresponsive polymer in water by pillararene-based host–guest interactions. The LCST value of the polymer increases upon the stepwise addition of either of the two pillararene hosts. On account of the pH-responsiveness of the pillararene-based host–guest interactions, the recovery of the LCST is achieved by treatment with acid, reflecting the pH-responsive supramolecular control of the LCST

A Dual-Thermoresponsive Gemini-Type Supra-amphiphilic Macromolecular [3]Pseudorotaxane Based on Pillar[10]arene/Paraquat Cooperative Complexation

Herein, first we report the preparation of a thermoresponsive [3]­pseudorotaxane from cooperative complexation between a water-soluble pillar[10]­arene and a paraquat derivative in water. Then we successfully construct the first pillararene-based gemini-type supra-amphiphilic [3]­pseudorotaxane from the water-soluble pillar[10]­arene and a paraquat-containing poly­(<i>N</i>-isopropylacrylamide) based on this new molecular recognition motif in water. This macromolecular [3]­pseudorotaxane shows unique dual-thermoresponsiveness. Furthermore, it can self-assemble into polymeric vesicles at 37 °C in water. These vesicles can be further used in the controlled release of small molecules induced by cooling to 25 °C or heating to 60 °C

Molecular Recognition Under Interfacial Conditions: Calix[4]pyrrole-Based Cross-linkable Micelles for Ion Pair Extraction

An anthracene-functionalized, long-tailed calix[4]­pyrrole <b>1</b>, containing both an anion-recognition site and cation-recognition functionality, has been synthesized and fully characterized. Upon ion pair complexation with FeF₂, receptor <b>1</b> self-assembles into multimicelles in aqueous media. This aggregation process is ascribed to a change in polarity from nonpolar to amphiphilic induced upon concurrent anion and cation complexation and permits molecular recognition-based control over chemical morphology under interfacial conditions. Photoirradiation of the micelles serves to cross-link the anthracene units thus stabilizing the aggregates. The combination of ion pair recognition, micelle formation, and cross-linking can be used to extract FeF₂ ion pairs from bulk aqueous solutions. The present work helps illustrate how molecular recognition and self-assembly may be used to control the chemistry of extractants at interfaces

Supramolecular Properties of a Monocarboxylic Acid-Functionalized “Texas-Sized” Molecular Box

A new carboxylic acid-functionalized “Texas-sized” molecular box <b>TxSB-CO</b>_<b>2</b><b>H</b> has been prepared by combining two separate building blocks via an iodide-catalyzed macrocyclization reaction. A single-crystal X-ray diffraction analysis revealed a paired “clip-like” dimer in the solid state. Concentration-dependent behavior is seen for samples of <b>TxSB-CO</b>_<b>2</b><b>H</b> as prepared, as inferred from ¹H NMR spectroscopic studies carried out in DMSO-<i>d</i>₆. However, in the presence of excess acid (1% by weight of deuterated trifluoracetic acid; TFA-<i>d</i>₁), little evidence of aggregation is seen in DMSO-<i>d</i>₆ except at the highest accessible concentrations. In contrast, the conjugate base form, <b>TxSB-CO</b>_<b>2</b>^–, produced in situ via the addition of excess triethylamine to DMSO-<i>d</i>₆ solutions of <b>TxSB-CO</b>_<b>2</b><b>H</b> acts as a self-complementary monomer that undergoes self-assembly to stabilize a formal oligomer ([<b>TxSB-CO</b>_<b>2</b>^–]<i>_n</i>) with a degree of polymerization of approximately 5–6 at a concentration of 70 mM. Evidence in support of the proposed oligomerization of <b>TxSB-CO</b>_<b>2</b>^– in solution and in the solid state came from one- and two-dimensional ¹H NMR spectroscopy, X-ray crystallography, dynamic light scattering (DLS), and scanning electron microscopy (SEM). A series of solution-based analyses carried out in DMSO and DMSO-<i>d</i>₆ provide support for the notion that the self-assembled constructs produced from <b>TxSB-CO</b>_<b>2</b>^– are responsive to environmental stimuli, including exposure to the acetate anion (as its tetrabutylammonium, TBA⁺, salt), and changes in overall concentration, temperature, and protonation state. The resulting transformations are thought to reflect the reversible nature of the underlying noncovalent interactions. They also permit the stepwise interconversion between <b>TxSB-CO</b>_<b>2</b><b>H</b> and [<b>TxSB-CO</b>_<b>2</b>^–]<i>_n</i> via the sequential addition of triethylamine and TFA-<i>d</i>₁. The present work thus serves to illustrate how appropriately functionalized molecular box-type macrocycles may be used to develop versatile stimuli-responsive materials. It also highlights how aggregated forms seen in the solid state are not necessarily retained under competitive solution-phase conditions

Fluorinated Nonporous Adaptive Cages for the Efficient Removal of Perfluorooctanoic Acid from Aqueous Source Phases

Per- and polyfluoroalkyl substances (PFAS) accumulate in water resources and pose serious environmental and health threats due to their nonbiodegradable nature and long environmental persistence times. Strategies for the efficient removal of PFAS from contaminated water are needed to address this concern. Here, we report a fluorinated nonporous adaptive crystalline cage (F-Cage 2) that exploits electrostatic interaction, hydrogen bonding, and F–F interactions to achieve the efficient removal of perfluorooctanoic acid (PFOA) from aqueous source phases. F-Cage 2 exhibits a high second-order kobs value of approximately 441,000 g mg–1 h–1 for PFOA and a maximum PFOA adsorption capacity of 45 mg g–1. F-Cage 2 can decrease PFOA concentrations from 1500 to 6 ng L–1 through three rounds of flow-through purification, conducted at a flow rate of 40 mL h–1. Elimination of PFOA from PFOA-loaded F-Cage 2 is readily achieved by rinsing with a mixture of MeOH and saturated NaCl. Heating at 80 °C under vacuum then makes F-Cage 2 ready for reuse, as demonstrated across five successive uptake and release cycles. This work thus highlights the potential utility of suitably designed nonporous adaptive crystals as platforms for PFAS remediation

Redox-Responsive Amphiphilic Macromolecular [2]Pseudorotaxane Constructed from a Water-Soluble Pillar[5]arene and a Paraquat-Containing Homopolymer

Here we report a redox-responsive host–guest complex between a new water-soluble pillar[5]­arene (<b>WP5</b>) and a paraquat derivative. Compared with the neutral form of the paraquat derivative that binds <b>WP5</b> weakly, its dication form binds <b>WP5</b> much more strongly. Furthermore, we utilize this new water-soluble redox-responsive molecular recognition motif to construct the first pillararene-based amphiphilic macromolecular [2]­pseudorotaxane, which self-assembles into redox-responsive polymeric vesicles in water. Such pillararene-based supramolecular vesicles were further used to construct a drug delivery system to encapsulate and controlled release DOX·HCl, an anticancer drug. The uptake of these DOX·HCl-loaded supramolecular vesicles by cancer cells was studied with confocal laser scanning microscopy. Meanwhile, DOX·HCl-loaded supramolecular vesicles showed anticancer activity in vitro comparable to free DOX·HCl under the examined conditions

Supramolecular Properties of a Monocarboxylic Acid-Functionalized “Texas-Sized” Molecular Box

A new carboxylic acid-functionalized “Texas-sized” molecular box <b>TxSB-CO</b>_<b>2</b><b>H</b> has been prepared by combining two separate building blocks via an iodide-catalyzed macrocyclization reaction. A single-crystal X-ray diffraction analysis revealed a paired “clip-like” dimer in the solid state. Concentration-dependent behavior is seen for samples of <b>TxSB-CO</b>_<b>2</b><b>H</b> as prepared, as inferred from ¹H NMR spectroscopic studies carried out in DMSO-<i>d</i>₆. However, in the presence of excess acid (1% by weight of deuterated trifluoracetic acid; TFA-<i>d</i>₁), little evidence of aggregation is seen in DMSO-<i>d</i>₆ except at the highest accessible concentrations. In contrast, the conjugate base form, <b>TxSB-CO</b>_<b>2</b>^–, produced in situ via the addition of excess triethylamine to DMSO-<i>d</i>₆ solutions of <b>TxSB-CO</b>_<b>2</b><b>H</b> acts as a self-complementary monomer that undergoes self-assembly to stabilize a formal oligomer ([<b>TxSB-CO</b>_<b>2</b>^–]<i>_n</i>) with a degree of polymerization of approximately 5–6 at a concentration of 70 mM. Evidence in support of the proposed oligomerization of <b>TxSB-CO</b>_<b>2</b>^– in solution and in the solid state came from one- and two-dimensional ¹H NMR spectroscopy, X-ray crystallography, dynamic light scattering (DLS), and scanning electron microscopy (SEM). A series of solution-based analyses carried out in DMSO and DMSO-<i>d</i>₆ provide support for the notion that the self-assembled constructs produced from <b>TxSB-CO</b>_<b>2</b>^– are responsive to environmental stimuli, including exposure to the acetate anion (as its tetrabutylammonium, TBA⁺, salt), and changes in overall concentration, temperature, and protonation state. The resulting transformations are thought to reflect the reversible nature of the underlying noncovalent interactions. They also permit the stepwise interconversion between <b>TxSB-CO</b>_<b>2</b><b>H</b> and [<b>TxSB-CO</b>_<b>2</b>^–]<i>_n</i> via the sequential addition of triethylamine and TFA-<i>d</i>₁. The present work thus serves to illustrate how appropriately functionalized molecular box-type macrocycles may be used to develop versatile stimuli-responsive materials. It also highlights how aggregated forms seen in the solid state are not necessarily retained under competitive solution-phase conditions