Supramolecular Nanostructures Based On Calixarenes

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Title: Supramolecular Nanostructures Based On Calixarenes
Author: Xu, Heng
Abstract: This dissertation describes a systematic approach towards the design , synthesis , characterization , and application of calixarene -based supramolecular nanostructures . Chapter 1 briefly overviews the field of supramolecular chemistry and highlights its horizons . Chapter 2 introduces a modular strategy towards synthesis of nanoscale receptor macromolecules - -calix -peptide conjugates . This strategy combines the unique host -guest capabilities of calixarene chemistry with synthetically flexible peptide synthesis . A series of calixarene amino acids was prepared and further utilized to synthesize calixarene dipeptides . Through this approach , calixarene amino acids are now available to be incorporated into peptide networks and nanostructured biologically relevant materials . Chapter 3 demonstrates supramolecular applications of calixarene -peptide conjugates . These calixarene amino acids serve as building blocks for the construction of a novel type of calixarene peptide dendrimers . Calixarene amino acids , peptides , and peptide dendrimers containing tetra -ester functions at their lower rims can extract sodium cations from aqueous solutions . Calixarene -peptide conjugates , possessing urea moieties at the upper rim , were demonstrated to reversibly form self -assembling capsules and supramolecular polymers in apolar solvents . Chapter 4 shows how CO2 gas can be used to construct novel types of supramolecular polymers . These polymers employ both hydrogen bonding and dynamic , thermally reversible carbamate bonds . Addition of a competitive solvent , such as DMSO , breaks hydrogen bonding in the assembled structures but does not influence the carbamate linkers . On the other hand , thermal release of CO2 was easily accomplished but the hydrogen bonded capsules remained intact . Chapter 5 demonstrates functions of supramolecular , calix -peptide based polymers . A switchable , supramolecular polymer is introduced , which is held together through hydrogen bonding and reversibly precipitates -redissolves upon changing the pH . Precipitating , it entraps and stores guest molecules within the self -assembling capsules , incorporated within the polymeric chain . CO2 was used to build switchable , supramolecular polymeric materials , which has fluorescent properties . Formation of a cross -linked , porous supramolecular polymer leads to instant entrapment of organic guest species . These can be stored and then released upon changing solvent polarity , temperature , pH , and concentration .
URI: http : / /hdl .handle .net /10106 /489
Date: 2007-08-23


Supramolecular Nanostructures Based On Calixarenes. Available electronically from http : / /hdl .handle .net /10106 /489 .

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