Preparation And Properties Of Polyazomethines As Hole Transport Materials

An'information age'of the 21st century has arrived. Existing technology of information display has been unable to meet the requirements. Organic light emitting devices (OLED) flat panel display technology emerged.Hole transport material is one of the important materials in OLED device. Polymer hole transport materials have developed rapidly in just a few decades. In order to be used in the OLED device, polymer hole transport materials need to meet the following requirements:(1) it should have a higher thermal stability and mechanical processing; (2) it should form a small barrier with anode; (3) it should have a good film-forming ability; (4) it should have a good hole mobility.Polyazomethines are one of the unique classes of all aromatic conjugated polymers, which have good heat resistance and excellent optical performance. It is worth mentioning that the polymerization is at room temperature, and no other reaction occurs during the synthesis, which can be described as saving energy efficiently. Therefore, this study selects polyazomethine as the hole transport materials.As traditional polyazomethines are conjugated polymers, their solubility is poor, which will affect the solution polymerization process and limit its use. Thus we designed and synthesized a novel diamine monomer. After reacting with two dialdehyde monomers separately, we got two polymers having good solubility. We found that both of polyazomethines have good thermal properties.The 5% weight loss temperatures are all above 440℃, and the Tg's of polymers are all above 185℃. It was found that aromatic polyazomethines had better mechanical properties than aliphatic ones. Therefore, we further synthesized Polyazomethines with the main chain of aromatic.On this basis, we have synthesized three diamine monomers whose the main chain were triphenylamine structure. They reacted with three dialdehyde monomers separately to get eight kinds of polymers. These polymers have good thermal stability, improved solubility and good optical properties.According to UV-visible spectroscopy and cyclic voltammetry to calculate the energy levels, we found they are expected to use as hole transport materials. Single device are prepared subsequently. TOF test showed that all of these Polyazomethines have high hole mobility of 10-4 cm2V-1s-1. The introduction of the carbazole ring and thiophene ring is more effect. And the polymer has both carbazole ring and the thiophene ring showed the maximum hole mobility of 4.77×10-4 cm2V-1S-1. According to XRD test,we found all the Polyazomethines are amorphous.In summary, this thesis synthesized a series of polyazomethines. They all have good solubility and high thermal stability. They can be used as hole transport materials. Some of them have good optical properties, and high hole mobility. They may be used in OLED devices as a hole transport material.