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Synthesis, structural and supramolecular studies of linear and cyclic 2 1-[α/aza]-oligomers

Abstract : The first part of this thesis reported the synthesis and structural studies of linear and cyclic 2:1-[α/aza]-oligomers possessing hydrophobic and/or basic amino acids (lysine). NMR and FTIR results demonstrated that the oligomers could adopt β-turn conformations in solution. Molecular dynamic calculations for oligomers based lysine residues reflected the important role of the aza-motif(s) in structuring the backbones regardless the chirality and nature of the amino acids. In the other hand, X-ray, FTIR, and NMR studies showed that homo- and heterochiral cyclo-(L- or D-Phe-azaPhe-Ala)2-hexamers adopt β-turn conformations in solution and solid states. Both molecules could organize into 3D highly ordered structures stabilized by hydrogen bonds and π-stacking. The second part reflected the propensity of some 2:1-[α/aza]-oligomers to self-assemble in some solvents to form supramolecular gels. Interestingly, the heterochiral cyclo-(D-Phe-azaPhe-Ala)2-hexamer could form organogels. The spectroscopic and rheological studies of the organogels revealed good thermal and mechanical stability with solid-like behavior. SEM and TEM images of the aerogel showed fibrous structure. Furthermore, two hydrogelators, Fmoc-D- or L-Phe-azaPhe-Ala-OH, have been developed and they could achieve hydrogels at pHs 7.0 and 10.0. UV and Flu studies demonstrated that the hydrogels are supported by π-stacking between the aromatic groups. CD analysis reflected that the two hydrogelators self-assemble into β-sheet like structure in consistent with ATR-FTIR results. Both hydrogels exhibited solid-like behavior through rheological studies and the SEM analysis of the xerogels revealed fibrous structure. The third part offered two applications; (i) oligomers based lysine residues reflected good performances in CO2/N2 separation when used as additives in polymeric Pebax® membrane, and (ii) the heterochiral cyclo-(D-Phe-azaPhe-Ala)2-hexamer is suitable for phase selective gelation with good recovery percentages
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Submitted on : Thursday, October 25, 2018 - 2:59:42 PM
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  • HAL Id : tel-01905002, version 1



Ibrahim Mohamed Ibrahim Abdelmoneim. Synthesis, structural and supramolecular studies of linear and cyclic 2 1-[α/aza]-oligomers. Chemical and Process Engineering. Université de Lorraine, 2017. English. ⟨NNT : 2017LORR0159⟩. ⟨tel-01905002⟩



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