Browsing by Author "Eghbali Dogaheh, Seyed Babak"

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    An investigation into the functionalization of poly(styrene-co-maleic anhydride) with calixarenes and their potential applications
    (Stellenbosch : Stellenbosch University, 2019-12) Eghbali Dogaheh, Seyed Babak; Arnott, Gareth E.; Mallon, P. E.; Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science.
    ENGLISH ABSTRACT: This work describes the development of a new method for the synthesis of a calixarene grafted polymer. The method involves synthesizing a mono-alkylated calixarene that contains an amino-tether suitable for grafting onto polymers such as the polystyrene-maleic anhydride copolymer (PSMA). The amino-tether was synthesized through a Gabriel synthesis on the parent phthalimide-derivatized calix[4]arenes. Having successfully optimized the method, the next stage investigated the potential applications for this technology. Two divergent applications were investigated: 1) a colorimetric mercury sensor, and 2) supramolecular hydrogel formation. The first application was based on the known sensing ability of functionalized calixarenes for the detection of different guests (cations, anions, neutral species, etc.). The most interesting one has been the colorimetric approach. Of interest in this work was the reported distal bis- allyl bis-arylazo calix[4]arene (also known as Chung’s sensor), which is capable of detecting mercury cations with a rapid color change in the solution media (yellow to pink). Therefore, a polymer-supported version of the same calix[4]arene was targeted for synthesis to facilitate the formation of a sensing instrument for mercury. Despite all efforts (trying eight synthetic routes), the required functionalized calixarene could not be obtained. Several suggestions for future work have been offered to solve this challenge. The second application aimed at in this project was to attach water-soluble calix[4]arenes to PSMA in order to make the polymer water soluble and to form a potential hydrogel. The most well-studied compound in this category has been the p-sulfonated calix[4]arene, which has been shown to form supramolecular complexes with bis-quaternary amines in aqueous solution. The possibility to achieve hydrogelation through a p-sulfonated calix[4]arene-grafted PSMA was therefore investigated. The primary amine-tethered p-sulfonated calix[4]arene was successfully synthesized and grafted onto PSMA. Unfortunately, the resulting grafts were unable to form a hydrogel in the presence of multiple quaternary amine-based compounds in spite of varying a large number of experiment parameters (i.e. stoichiometry, pH, temperature, concentration and so forth). One problem was that the grafts were not as water soluble as expected. Thus a second option was to replace PSMA with another polymer with higher water solubility upon grafting with the calix[4]arene. The polymer investigated was a polyvinylpyrrolidone maleic anhydride copolymer (PVP-MA). The grafting reaction was successfully carried out and much higher water solubility for the graft was achieved, but once again a hydrogel could not be formed. It is believed that this failure most likely is due to the conformational issue of the calix[4]arene or the low degree of functionalization for the grafts. Several solutions to this these failures have been proposed.