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ÖgeStimuli responsive and self-healing calix[4]pyrrole based supramolecular gels constructed by anion recognition(Graduate School, 2024-07-25) Ünlü, Fatma Yelda ; Aydoğan, Abdullah ; 509182284 ; ChemistrySupramolecular chemistry is a branch of chemical sciences focused on investigating structures formed by the reversible intermolecular interactions between two or more molecules. These interactions, which are non-covalent in nature, include ion, ion-dipole, van der Waals, hydrophobic interactions, host-guest interactions, and hydrogen bonds, among others, that bind supramolecular structures together. Even though non-covalent interactions are weaker than covalent bonds individually, the significant quantity of these interactions contributes to the overall stability within a typical supramolecular system. Supramolecular polymers are assemblies created through the reversible and highly directed interactions among monomers. Through these interactions, supramolecular polymers can respond to external stimuli such as heat, light, chemicals, and redox reactions. Enhancing the physical properties of supramolecular polymers, such as high strength and self-healing capabilities, can be accomplished by creating cross-linked polymers and gels. Supramolecular gels are materials in which monomers are cross-linked through reversible non-covalent interactions. Combining the elastic properties of solids with the low viscosity of liquids, supramolecular gels represent ideal candidates for synthesizing smart materials having responsiveness to external factors. The responsive ability of supramolecular gels to external factors such as temperature, stress and light, along with their capability to self-repair, emphasizes the significance of these materials. Moreover, the controllability of these properties further enhances the importance of supramolecular gels. Besides, supramolecular hyperbranched polymers, another type of supramolecular cross-linked polymers, possess a unique combination of features from both supramolecular polymers and hyperbranched polymers. These include reversible and adjustable properties, high solubility, responsiveness to stimuli such as pH, temperature, and light. These materials can be prepared from a variety of supramolecular hosts such as crown ethers, porphyrins, cucurbit[n]urils, and pillar[5]arenes when they combined with cationic or neutral guest species. However, in the literature, there is a lack of studies concerning supramolecular cross-linked and hyperbranched polymers constructed from anionic guest species. At this point, calix[4]pyrroles emerge as notable candidates due to their capability for binding anions. In this thesis, it was aimed to construct novel calix[4]pyrrole based cross-linked supramolecular polymers and gels by means of anion recognition. Three articles have been published related to this Ph.D. thesis. Each study was presented in separate chapters. The first study is mentioned in chapter 2 and describes calix[4]pyrrole based supramolecular polymer networks that are prepared based on host-guest interactions constructed through anion recognition. For this purpose, two different 3A type host molecules, comprising three calix[4]pyrrole rings linked to benzene cores with different linker lengths, were synthesized by copper catalyzed azide-alkyne click reaction using azide functionalized benzenes and alkyne-functionalized calix[4]pyrroles to investigate the impact of the chain length difference. Additionally, a BB-type guest molecule, tetrabutylammonium salt of suberic acid containing carboxylate units at both terminals, was synthesized and is capable of forming complexes with 3A-type host molecules. Following that, the interactions between the 3A and BB type host-guest systems were examined to investigate the complexation and supramolecular network formation in two different solvents: chloroform and acetonitrile. Due the better supramolecular polymer network formation in acetonitrile, the further analyses were conducted only in acetonitrile, employing concentration dependent NMR, viscosity measurements, DOSY (Diffusion-Ordered Spectroscopy) NMR and DLS (Dynamic Light Scattering) analyses. It was also observed that the the supramolecular polymer networks are responsive to external stimuli such as temperature, pH, and competing fluoride anion. The supramolecular polymer network with longer spacer length from the benzene core were also found to demonstrate self-healing ability. Spherical aggregates in zero dimension (0D), fibers in one dimension (1D), porous materials in two dimension (2D) and adhesive materials in three dimension (3D) were obtained by means of various fabrication techniques. The second study mentioned in chapter 3 introduces a cross-linked supramolecular polymer based on a calix[4]pyrrole decorated pillar[5]arene. Pillar[5]arene macrocycle was used as a skeleton to prepare the decacalix[4]pyrrole decorated host system. The target compound was synthesized via a copper catalyzed azide-alkyne click reaction using and alkyne-functionalized calix[4]pyrrole and azide-functionalized pillar[5]arene. Tetrabutylammonium salts of terephthalic acid and suberic acid as two different cross-linker guests were used to see the chain length effect. Anion recognition based cross-linked supramolecular polymer was formed by means of hydrogen bonding between carboxylate units of cross linker and calix[4]pyrrole units of decacalix[4]pyrrole monomer in chloroform. The cross-linked system was analyzed by a combination of concentration dependent NMR, viscosity measurements, DOSY NMR and SEM (Scanning electron microscopy) measurements. Efficient cross-linked supramolecular polymer formation was observed with suberate anion. Therefore, the supramolecular polymerization and further experiments were conducted with tetrabutylammonium salt of suberic acid. It was also seen that the cross-linked supramolecular polymer showed temperature and competing anion (fluoride anion) responsiveness. As application, cross-linked supramolecular polymer was utilized for the removal of micropollutants from water, specifically targeting three cationic pollutants; methylene blue (MB), rhodamine B (RB) and methyl violet 2B (MV). Micropollutant removal experiments were carried out both in solid and gel forms of cross-linked supramolecular polymer. The solid form exhibited superior removal efficiency for methylene blue and methyl violet 2B, while the gel form demonstrated higher removal efficiency for rhodamine B. The third study mentioned in chapter 4 focuses on a multi responsive AB2 type hyperbranched supramolecular polymer. AB2 type monomer was designed as a single calix[4]pyrrole core tethered with two carboxylate units at its alternating meso-positions. Hyperbranched supramolecular polymer was achieved through self-assembly via anion recognition between carboxylate units and calix[4]pyrrole core in acetonitrile. The obtained polymer was characterized by concentration dependent NMR, viscosity measurements, DOSY NMR, SEM measurements, TEM (Transmission electron microscopy) and DLS analyses. It was seen that the hyperbranched supramolecular polymer displayed responsiveness to temperature, pH and chemical stimuli (Calix[4]pyrrole]. Additionally, a range of morphologies were observed spanning from ellipsoidal aggregates to crystalline morphologies depending on variations in concentration.
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ÖgeStimuli responsive supramolecular polymers and ida sensors based on host-guest interaction and ion pair recognition ability of calix[4]pyrroles(Lisansüstü Eğitim Enstitüsü, 2021) Amharar, Sana ; Aydoğan, Abdullah ; 710239 ; KimyaCalix[4]pyrroles are the macrocyclic compounds with four pyrrole units connected to each other via sp3 carbon atoms. Their anion binding ability in organic solvent has make them gain attention in the sensing area. It is cost-effective, easy to synthesize and to modify. This thesis is divided into four parts, first chapter corresponding to an introduction about generality in supramolecular chemistry and calix[4]pyrroles, and the next three different chaptersare based on the three articles published during this PhD study. In Chapter 2, supramolecular polymerization of calix[4]pyrroles bearing tethered carboxylate functional groups was reported in the form of their tetrabutylammonium salts. At high concentrations one of the calix[4]pyrroles with a shorter linker between the calixpyrrole core and the carboxylate unit was found to give a thermoresponsive supramolecular polymer gel. In Chapter 3, rationally designed ion pairs were integrated into a calix[4]pyrrole skeleton, resulting the formation of an ion pair recognition based linear supramolecular polymer. The effect of simultaneous host-guest and cation- interactions between carboxylate functional calix[4]pyrrole and cetyltrimethylammonium cation was investigated by NMR, viscosity, SEM, and DSC analyses. The resulting supramolecular polymer was found to show temperature induced rapid and reversible sol-gel transition through van der Waals interactions of cetyl units. And finally in chapter 4, cost-effective fluorescence turn-on indicator-displacement-assay (IDA) sensors based on octamethylcalix[4]pyrrole receptor and tetrabutylammonium salts of 4-methylumbelliferone and fluorescein indicators were developed for highly sensitive detection of fluoride anion. The IDA sensor assembly relies on the hydrogen bonding between calix[4]pyrrole and carboxylate units of indicators and further displacement of receptors with target analyte. While all the sensors displayed rapid and selective sensitivity towards fluoride over the other anions, 4-methylumbelliferone based IDA system was also found to have a visual color change for the sensing of fluoride anion. The experimental results revealed that fluorescein-based IDA sensor could be used for the sensing of fluoride anion with a detection limit as low as 3.2 nM.