Synthesis And Self-Assembly Of Rigid-flexible Block Oligo-isomers With Conjugated Rod Segments

Rod-coil molecules, consisting of a flexible and a rigid block, have a strong affinity to self-organize into various supramolecular nanostructures in the bulk state. Self-assembly of rod-coil molecules are widely studied due to their remarkable application prospects as good light, electricity, functional magnetic advanced functional nanomaterials and molecular devices. In this thesis, two series of rectilinear rod-coil molecules with varying length were designed and successfully synthesized, the molecular structures are characterized by NMR and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectroscopy. The self-assembling behaviors of these molecules was investigated by means of differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and small-angle X-ray scattering (S AXS) in the bulk state.Firstly, three pairs of isomers were synthesized. These molecules consist of conjugated rod segments, which are composed of phenylene, biphenylene and carbon-carbon triple bond (C= C), connecting poly(ethylene oxide) (PEO) with different degree of polymerization (DP) and poly(propylene oxide) (PPO) with a DP of 7 as coil segments, and their self-assembly behavior was investigated in the bulk state. The result indicates that the biphenylene as the center of rod segments have a liquid crystalline phase, however, isomers directly tranfer from a solid to isotropic liquid. Their phase transition tempreture reduces, as the flexible chain increases.In addition, four pairs of isomers were synthesized. Increasing the length of rod segments, the self-assembly of molecules are more diversified, and can organized into body-centered tetragonal, hexagonal close-packed,and so on. The main reason can be classified into two points, the one is that a different sequence of conjugated rod segments of molecular isomers dramatically influences the driving force of π-π stacking interactions of rod-coil molecular architecture. The other is that length of rod segments, volume fraction and different kinds of flexible chain can also influence the structures of supramolecules.