Synthesis And Self-Assembly Properties Of Z-shaped Rod-Coil Molecules Based On Pyrene Poly(Ethylene Glycol) Monomethyl Ether

In this paper,four series of Z-shaped rod-coil molecules based on pyrene and poly(ethylene glycol)monomethyl ether were successfully synthesized.The molecular structures are characterized by 'H-NMR and MALDI-TOF-MASS spectroscopy.The self-assembly behaviors of these molecules in bulk state were investigated by means of differential scanning calorimetry(DSC),X-ray diffraction(XRD),and their aggregation behaviors in aqueous solution were studied by using Fluorescence spectra(FL),scanning electron microscopy(SEM)and atomic force microscope(AFM).In the second chapter,the Z-shaped rigid flexible molecules 2-1,2-2,2-3 with different length of flexible chain are designed and synthesized.The purpose of this study is to investigate the influence of linear flexible chain length on self-assembly.The experimental results show that three molecules have no liquid crystal phase in bulk,and the melt transition temperature decreases with the increase of the volume fraction of the flexible chain.Molecule 2-1 self-assemble a lamellar structure,2-2 and 2-3 form a disorder structure because of the larger volume fraction of flexible chain.Fluorescence emission spectra show that 2-1,2-2,and 2-3 are aggregated in aqueous solution.2-1 forms a cross linked reticular fibrous structure with a length of 900 nm and 2-2 forms an irregular granular structure with particle size of 500-1100 nm,2-3 forms a linear fiber structure with the length of 2300 nm.In the third chapter,The Z-shaped molecules 3-1,3-2,3-3 with dendritic flexible chain are designed and synthesized.The purpose of this study is to investigate the influence of the length of dendritic flexible chain on the self-assembly.The experimental results show that the three molecules have no liquid crystal phase in bulk self-assembly,and the melt transition temperature decreases with the increase of the volume fraction of the dendritic flexible chain.The molecular 3-1 forms a bicontinuous cubic structure,and 3-2,3-3 form a layered structure because of the increase of the volume fraction of the flexible chain.The results of fluorescence spectra show that the three kinds of molecules can aggregate in aqueous solution.The SEM experiment indicated 3-1,3-2,3-3 self-assemble into granular structure with particle diameter of 140 nm,240 nm,260 nm.When the solution concentration is increased to 0.01 w%,the fiber structure is formed from 3-1,and 3-2 forms a clockwise rotating sunflower sheet,and 3-3 forms a granular structure by AFM experiment.In the fourth chapter,Z-shaped rod-coil molecules 4-1 and 4-2 which have the double branches flexible chain were designed and synthesized.The purpose of this study is to investigate the influence of the position of flexible chain on the molecular self-assembly structure with the same volume fraction of flexible chain.The experimental results show that the two kinds of molecules have no liquid crystalline phase,and the melting point of the two molecules is very different.4-1,4-2 self-assemble a layered structure at the solid state.The fluorescence spectrum experiments show that two kinds of molecules can self-assemble in aqueous solution.The SEM experiment reveal that 4-1 and 4-2 can form granular structure with particle diameter of 92 nm and 80 nm.A larger granular structure can be formed by increasing concentration through AFM experiment.In the fifth chapter,Z-shaped rod-coil molecules 5-1 and 5-2 with different length of rod were designed and synthesized.The effect of different length of rigid block on the self-assembling structure is investigated at the same volume fraction of flexible chains.The experimental results show that 5-1 has a liquid crystalline and forms a lamellar structure,and 5-2 has no liquid crystalline phase and self-assembled into a two-dimensional hexagonal columnar structures at the solid state.The fluorescence experiments show that two kinds of molecules have been gathered in aqueous solution.The SEM experiment reveal the short fiber structure is formed form 5-1 and 5-2 with the length of 950 nm,1200 nm.The results obtained by AFM experiment are consistent with SEM experiment coming from 5-1 and 5-2.