Electronic Memory Characteristics Of Pyrazoline-based Small Molecules And Side-chain Polymers

Over the past few decades, tremendous efforts have been made on the investigation of resistive switching memory for the growing demand of next-generation information and communication technology. As the most promising alternatives to their traditional inorganic counterparts, the memory devices based on resistance-switchable organic/polymer materials have the advantages of low cost, low operation voltage and high packing density. Currently, the investigations on organic storage materials are contained to several compound groups such as azo, naphthalimide and so on. For understanding device physics and improving the device performance, developing new materials is of great importance. Pyrazoline have been widely used as optoelectronic devices, aggregation-induced emission, fluorescence probe and biological activity because of their strong fluorescence and good capability for hole-transporting. However, the application of pyrazoline derivatives in organic electrical memory materials has been rarely reported, to the best of our knowledge. Therefore, we designed and synthesized a series of pyrazoline-based organic small molecules and side-chain polymers, and then studied their electrical memory characteristics. The main research contents include the following aspects:(1) We synthesized a simple three aryl substituted pyrazoline small molecules(ATPP), and investigated their electrical memory characteristics, founding that the prepared devices show “fall” phenomenon that indicates the unstable high conducting state. In order to overcome this defect, we further prepared the ATPP-based hyperbranched polymers(HPPS), and the HPPS-based devices exhibited excellent SRAM memory characteristics.(2) On the basis of ATPP molecule, we introduced naphthalimide group, synthesizing three different R-substituted pyrazoline small molecules(4ac, 4ad, 4ae), and explored the effect of different substituted groups on storage properties. In order to simplify the devices and consider the influence of the conformation change of polymeric side-chain groups under the electric field, we also synthesized three short chain polymers(6ac, 6ad, 6ae) and three long chain polymers(6bc, 6bd, 6be), and investigations indicated that these two kinds of compounds exhibited different electrical memory behaviors.(3) On the basis of pyrazoline small molecules(4ac, 4ad, 4ae), we introduced nitro group into the aryl in three position of pyrazolin ring, preparing the ATRP initiator(IN) with the strong electron withdrawing effect, and initiated the polymerization of carbazole monomer(MCz) with the strong electron donating effect. Finally, the end-functionalized D-A polymers(PMCz-IN) were prepared to compare with the doped polymers(PMCz-IN) on the electrical memory characteristics.Learning from the above system research, we overcome the defects of three aryl substituted pyrazoline in the electric storage performance, making use of the prepared hyperbranched polymer. This provides a good reference for the development of new materials for electric storage stability. In addition, through the investigation of substituent effect of pyrazoline derivatives, the length effect of side-chain polymers and end-functionalized polymers, we improve the research progress of pyrazoline in the field of electrical memory performance.