Synthesis,Molecular Stacking Patterns And Potential Applications Of Bola-type And Tetraphcnylethene-substituted Dipeptides

During the last decades,amino acids and peptide compounds as life-related substances have been widely studied due to their biomimetic structure,biocompatibility,degradability and structural programmability.Modification of the peptide molecular structure can drive the molecules self-assemble into specific structures and show specific functionalities.These organic self-assemblies can be applied for the preparation of advanced materials.This thesis aims at studying the self-assembly behaviors of a series of bola-type dipeptides and the odd-even effect on the molecular packing structure.The application of bola-type dipeptides in 3D gel printing and that of tetraphenylethene-substituted dipeptides in organic-inorganic hybrid material fabrication were also studied.The results are shown as followingFirstly,the odd-even effect of the alkylene chain controls the morphology of the self-assembly and the molecular packing structure in the self-assembly.For the bola-type Ala-Ala dipeptides with different carbon bridge lengths,the molecules with even-numbered carbon bridges self-assembled into twisted nanoribbons,while those with odd-numbered carbon bridges self-assembled into straight belts.FT-IR spectra indicated that the dipeptides with even-numbered and odd-numbered carbon bridges formed hydrogen bonds in different ways.X-ray diffraction patterns revealed that molecules with odd-and even-numbered carbon bridges stacked in monoclinic and triclinic structures,respectively.Secondly,for the bola-type Ala-Phe dipeptides,homochiral dipeptides self-assembled into twisted nanoribbons,while heterochiral dipeptides self-assembled into helical nanofibers,the handedness of the self-assemblies was controlled by the chirality of the phenylalanine near the C-terminal.FT-IR spectra indicated that homochiral and heterochiral dipeptides formed hydrogen bonds in different ways.The difference in the ?-? stacking among phenyl groups of the molecules during the assembly process ultimately leads to differences in the molecular stacking modes.The dipeptides can cause physical gels in polymerizable solvents,indicating an application for 3D printingThirdly,the organic-inorganic hybrid silica was prepared using tetraphenylethene-substituted Phe-Phe dipeptides and TEOS,which showed optical activity.The diameter of the organic fiber increased after being covered by silica.