含1,2,3-三氮唑液晶化合物及多苯環芳香族亞醯胺衍生物之合成與分子自組裝及其在有機薄膜電晶體之研究

Abstract

The goal of this research is to study the self-assembly of small molecules and polymers. The first part of this study is focused on the synthesis and self-assembled nanostructures of 1,2,3-triazole liquid crystals via click chemistry. The second part is to study the synthesis of polycyclic aromatic diimide derivatives and their application on the solution-processed n-type organic thin-film transistors. In the first part, a series of novel chiral amphiphilic liquid crystals, which contain 4-[1,2,3]-triazolephenyl 4-alkoxybenzoate mesogens and β-D-galactopyranoside end-group, were synthesized. All obtained compounds were exhibited a chiral smectic A phase. The self-assembling behavior of these liquid crystal amphiphiles in the solution, which exhibited high segregation strength for phase separation, was studied by electron microscopy. The morphological transformation of self-assembled chiral amphiphilic liquid crystals, from a platelet-like morphology to helical twists, was obtained by increasing the length of the hydrophobic alkyl tail. In addition, three kinds of chiral saccharide-containing liquid crystalline acetylenic monomers were prepared by click reaction between 2-azidoethyl-2,3,4,6-tetraacetyl-β-D-galactopyranoside and 1-biphenyl- acetylene 4-alkynyloxybenzoate. The obtained monomers were polymerized by WCl6-Ph4Sn to form three side-chain LC polyacetylenes. All monomers and polymers show a chiral smectic A phase. Self-assembled hiearchical superstructures of the chiral saccaride-containing LCs and LCPs in solution state were studied. Due to the LC behavior, these molecules exhibit a high segregation strength for phase separation in dilute solution. The self-assembled morphology of LC monomers was dependent upon the alkynyloxy chain length. Increasing the alkynyloxy chain length caused the self-assembled morphology to change from a platelet-like texture (K6E) to helical twists morphology (K11E and K12E). Furthermore, the helical twist morphological structure can be aligned on rubbed polyimide layer to form two dimensional ordered helical patterns. In contrast to LC monomers, K11P was self-assembled into much more complicated morphologies, including nanospheres and helical nanofibers. These nanofibers are evolved from the helical cables ornamented with entwining nanofibers upon natural evaporation of the solution in a mixture with a THF/methanol ratio of 3:7. The second part of the work is mainly devoted to the development of new soluble and air-stable n-ytpe semiconducting materials. The synthesis and comprehensive characterization of 20 organic semiconductors comprised of four different sizes of polycyclic aromatic cores and five different fluorinated substituents are described. The influences of the structural modifications of the fluorinated substituent, spacer and central core on the charge mobility were examined. Top contact/botton gate organic thin film transistor devices were constructed by spin-coating process of these derivatives on SiO2/Si wafer that had been pretreated with hexamethyldisilazane (HMDS). The electrical characterization of all devices was accomplished in a nitrogen atmosphere as well as in air. The mobilities of P(1), P(2) and P(3) were measured to be 4.71×10-9, 1.03×10-8, and 4.3×10-8 cm2V-1s-1, respectively. With longer spacer inserted between perylene core and fluorinated dendrons, the mobility is increased. The highest mobilities of P(-) and PCl(-) are 3.88×10-4 and 5.31×10-4 cm2V-1s-1, respectively, as measured in the glove-box. However, only PCl(-) shows good OTFT behavior and comparable mobility of 3.61×10-4 cm2V-1s-1 as measured in air. The result demonstrates that Cl4-PTCDA core (perylene with 4 chloro substituents) can serve as a good candidate for OTFT.