Synthesis And Self-assembly Properties Of Ⅴ-Shaped Rod-Coil Molecules Based On Pyrene

In this paper,three series of V-shaped rod-coil molecules which contain pyrene on the rod building block were successfully synthesized.The molecular structures are characterized by 1H-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(SAXS),and their aggregation behaviors in aqueous solution were studied by using Fluorescence emission spectra,Scanning electron microscopy(SEM)and Atomic force microscope(AFM).In the second chapter,V-shaped rod-coil molecules 1a,1b and 1c with different length of flexible chain were designed and synthesized.Two biphenyls were attached to 1,8 positions of pyrene by ethynyl as the rigid rod block,the molecular weight of the polyethylene glycol monomethyl ether 350,550,750 attached to the end of the biphenyls as the flexible block.By adjusting the length of the flexible chain to study the impact on the self-assembly morphology.In bulk state,molecules 1a,1b and1c have no liquid crystalline phase,all of which can self-assemble into rectangular columnar structure in the solid state.This means that for a single branch of the V-shaped rod-coil molecules,their flexible chain volume fraction is less than or equal to 0.58,however,it can still form an ordered rectangular columnar structure.In aqueous medium,three molecules can spontaneously aggregate.AFM and SEM results show that molecule la self-assembles into smaller spindle micelles,and molecule lb self-assembles into regular tetragonal structure and the linear fiber with increasing the concentration,and molecule 1c self-assembles into cylindrical rod micelle and bigger spindle micelles when the concentration was increased or the solvents was volatilized.In the third chapter,a series of V-shaped rod-coil molecules 1a,1b,1c which have three branches of flexible chain were designed and synthesized.Two biphenyls are attached to 1,8 positions of pyrene and the end of biphenyl connect 3,4,5-pyrogallol by ester group as the rigid rod block.The flexible block consists of diethylene glycol monomethyl ether,triethylene glycol monomethyl ether and tetraethylene glycol monomethyl ether.The impact of length variation of dendritic flexible chain on the self-assembly was studied.As is shown by the experimental results,though molecules 1a,1b,1c have no liquid crystalline phase,their self-assembly structures in the solid state are different.Molecule 1a can self-assemble into hexagonal columnar structure,both molecules lb and 1c can self-assemble into lamellar structure.This results means that repulsive force between the flexible chain is enlarged and the π-π stacking interaction between the rigid rod is damaged with increasing the length of flexible chain,and which leads to the orderly phase structure be unfavorable to form.In aqueous medium,as is shown by fluorescence spectroscopy and dynamic light scattering experiment,three molecules can spontaneously aggregate,and the radii of these aggregation are 93.0 nm,81.3 nm,70.0 run,respectively.In the fourth chapter,a series of V-shaped rod-coil molecules 1a,1b and 1c which have the double branches flexible chain was designed and synthesized.Two biphenyls were attached to 1,8 positions of pyrene and the end of biphenyl connects 3,5 resorcinol by ester group as the rigid rod block.The flexible blocks consist of triethylene glycol monomethyl ether,tetraethylene glycol monomethyl ether and hexaethylene glycol monomethyl ethers.The purpose of synthesizing such series of molecules primarily is compared with that of the molecules in the third chapter.When the volume fraction of flexible chains is the same,we want to study the impact of cross-sectional area variation of the flexible chains on the supramolecular self-assembly.In bulk state,molecule la,lb and lc have no liquid crystalline phase,however,both molecule la and lb can self-assemble into bicontinuous cubic phase,molecule lc can self-assemble into lamellar structure in solid state.This means that in such molecules,when their volume fraction of the flexible chain is equal to or less than 0.52,they can form ordered bicontinuous cubic structure.In aqueous medium,the fluorescence intensities of three molecules are obviously quenching and indicate they can spontaneously aggregate.The radii of these aggregation are 60.0 nm,58.0 nm and 358.0 nm by dynamic light scattering experiment,respectively.