Studies of poly(para-phenylene)s on their structures and properties relationships and of characterization on conformation of single conjugated polymer chain

• Main Authors: An-En Hsiao, 蕭安恩
• Other Authors: Show-An Chen
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/72030730780546300434

碩士 === 國立清華大學 === 化學工程學系 === 95 === My study includes two following parts. The first is to improve Yamamoto polycondensation to yield high molecular weight poly(para-phenylene)s (PPPs) and to characterize their properties. PPPs are one of the most important classes of conjugated polymers and have been the subject of extensive research, particularly as active materials for use in light-emitting diodes (LEDs) and solar cell. These materials have been particular interest as potential blue emitters in such devices. The two main polycondensation methods used are the Suzuki polycondensation of aryl halides with arylboronic acids and the Yamamoto polymerisation of aryl dihalides using nickel(0) reagents. Generally speaking, the Suzuki method yield higher molecular weight than the Yamamoto procedure, but is synthetically more demanding (refer to arylboronic acids). To improve Yamamoto method, Using THF as reaction solvent to substitute for DMF and toluene used in common Yamamoto polycondensation, the reaction reactivity can be increased resulting from good solubility for both Ni catalysts and polymers. We can obtain high-molecular weight PPP as Suzuki polycondensation did. Then we synthesize three high-molecular weight PPP derivatives: mono-substituted alkoxyl group (mR8O-PPP), di-substituted alkoxyl group (dR8O-PPP), and Cz capping on the ends of alkoxyl group (Cz-PPP), and to study their structure-property relationships. The incorporation of long alkyl-chain substitute on side chain can pack in order in thin film as cast from THF and thus increase conjugation; Cz on the ends of alkoxyl group for Cz-PPP can destroy the order pack in thin film and thus reduces conjugation. While doping with 8 wt% Ir-G complex, Cz-PPP has less phase separation because the Cz on the ends of alkoxyl group exhibits excellent chemical compatibility with guest material. The device (ITO/PEDOT/Polymer : dopant /CsF/Ca/Al) based on this material exhibits stable green emission (spectrum remains unchanged upon successive operation) and luminous efficiency of 14.31 cd/A (13.6 V, 0.85 mA/cm2), and the highest luminance of 3882 cd/m2 (24.8 V , 107.6 mA/cm2). And we can obtain better balance of carrier by inserting TPBI as hole-blocking layer. The second is to determine the conformation of single conjugated polymer chain. A technique for grafting a polymer to a solid metal or semiconductor surface is essential for the development of such applications. This is because the chemical and electrical connectivity between a polymer terminus and an electrode surface may have an important influence on effective electron or photon signal transportation. A high density polymer grafted on a surface is commonly called a polymer brush, and such polymers have been well investigated such as surface modification. In contrast, a low-density grafted polymer is useful for observing nanostructures and physical properties at a single polymer chain level. As a methodology for polymer grafting, we use two-phase (water-toluene) reduction of AuCl4- by sodium borohydride in the presence of an alkanethiol, the gold particles of average 2.6 nm diameters bearing a surface of thiol have been prepared and characterized by TEM and UV-Vis absorption. Then we synthesized end-functionalized PFO bearing thiolacetate (SH-PFO). Furthermore, with the chemisorption of thiolacetate modified polymer on a gold particle surface, we visualized the polymer connection onto particle surfaces by AFM and clearly observed dumbbells-type nanohybrids that consisted of the polymer bridging between two Au nanoparticles.