Tulli, Ludovico G.. Calixarene-based langmuir monolayers : from crystallization templates to metal organic networks. 2015, PhD Thesis, University of Basel, Faculty of Science.
Available under License CC BY-NC-ND (Attribution-NonCommercial-NoDerivatives).
Official URL: http://edoc.unibas.ch/diss/DissB_11742
Amphiphiles are compounds able to self-assemble in myriad supramolecular structures such as micelles, vesicles, nanosheets, nanorods, nanotubes and nanofibers, to name but a few. The shape of the resulting supramolecular assembly is dependent on the structure of the amphiphilic building block and type of solvent. Among all kinds of natural and synthetic amphiphiles, macrocyclic amphiphiles are of particular interest due to the possibility to conveniently control the hydrophilic/lipophilic balance of the final amphiphilic structure. The basket-like rigid conformation of calixarenes, and the possibility to selectively functionalize both the upper and lower rim, make these molecules attractive building blocks for the design of amphiphilic compounds.
Amphiphilic calixarenes that are essentially insoluble in water self-assemble as monomolecular films at the air-water interface, forming Langmuir monolayers, where the aliphatic chains point into air while the polar functions are immerged into the subphase. Langmuir monolayers of amphiphilic calixarene derivatives have been demonstrated to interact with a wide range of solutes, ranging from ions to macromolecules. In addition to this, calixarene-based monolayers have been shown to induce the interfacial crystallization of inorganic and organic solids. The polar heads of the macrocycles act as recognition units for the interfacial nucleation of the to-be-crystallized molecules. Electrostatic interactions, along with geometrical complementarity between the macrocycles polar functions and the solute are the determining factors for the interfacial crystal growth. In this thesis, the ability of Langmuir monolayers of a p-carboxycalixarene derivative to act as templates for the crystallization of gabapentin (GBP), an active pharmaceutical ingredient used to relieve neuropathic pain, with a control over its polymorphism is reported.
The suitable chemical modification of the upper and lower rim of calixarenes allows producing stable amphiphilic macrocycles able to form stable Langmuir monolayers at the air-water interface with strong affinities towards ions. The affinity of calixarene-based Langmuir monolayers towards ions is mainly owing to the presence of a cavity that allows for the encapsulation of the ions, coupled with multiple polar ligating functions at the p-positions that strongly interact with the solute. In this thesis, the recognition properties of Langmuir monolayers of a series of p-carboxy- and p-aminocalixarene derivatives towards strong, i.e. CuCl2, CoCl2, NiCl2 and MnCl2, and weak, i.e. HgCl2, electrolytes are reported. The effect of the inorganic compounds on the self-assembly properties of the calixarene-based Langmuir monolayers is investigated by means of surface pressure-area compression isotherms, Brewster angle microscopy (BAM) and synchrotron-based X-ray diffraction techniques. Notably, it has been demonstrated that the structure of the macrocycle has a crucial effect on its interfacial organization. Upon interaction of a long chain, i.e. C12, p-carboxycalixarene derivative with Cu2+ ions at the air-water interface, the corresponding calixarene-based monolayer is mainly amorphous. On the other hand, Langmuir monolayers of the short chain (C3), structural analogue on aqueous Cu2+ ions subphases possess significantly large and highly ordered structures. It is assumed that the interfacial self-assembly of the long chain p-carboxycalixarene derivative is mainly driven by van der Waals interactions among the aliphatic chains, which contribute to the partial disordered monolayer structure. On the contrary, the self-assembly of the short chain p-carboxycalixarene derivative is driven by π-π interactions among aromatic rings of neighboring amphiphiles, which contribute to the highly ordered structure of the monomolecular film.
|Advisors:||Meier, Wolfgang and Shahgaldian, Patrick and Dalgarno, Scott John|
|Faculties and Departments:||05 Faculty of Science > Departement Chemie > Chemie > Makromolekulare Chemie (Meier)|
|Bibsysno:||Link to catalogue|
|Number of Pages:||1 Online-Ressource (133 Seiten)|
|Last Modified:||05 Sep 2016 06:47|
|Deposited On:||05 Sep 2016 06:46|
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