Preparation Of Novel Polyimides And Research On Their Memory Characteristics

With the rapid development of information technology, memory devices are becoming faster respondence, higher-density storage, lower cost and so on. The traditional silicon-based memory materials could not meet the demand of the prospective market any more. So looking for alternative memory materials has been a research hotspot. Aromatic polyimides(PIs) have the high and low temperature resistance, low dielectric constant, flexibility and easy film forming ability. The research of memory characteristics of polyimides with new molecular structures is currently popular in the field of aromatic polymers.A series of aromatic diamines have been designed and synthesized base on carbazole. Diamines obtained were characterized by 1H NMR, 13 C NMR,FT-IR and elementary analysis. A series of novel organosoluble aromatic polyimides were successfully synthesized by using of diamines obtained reacting with dianhydrides such as 2,2’,3,3’-biphenyltetracarboxylic dianhydride(BBZPDA), 2,2’-diphenyl-4,4’,5,5’-biphenyltetracarboxylic dianhydride(DPBPDA), 2,2’-bis[4’’-(3’’’,4’’’,5’’’-trifluoro-phenyl)phenyl]-4,4’,5,5’-biphenyltetracarboxylic dianhydride(BTFBPDA). These polyimides were characterized by ultraviolet visible, fluorescence, thermal gravimetric analysis, different scanning calorimetry, cyclic voltammetry, elementary analysis and so on. The HOMOs and LUMOs orbital energy level were calculated from DET at the gaussian 09 with the wb97XD/6-31G(D, P) basis set. Devices with the PI films sandwiched between an ITO bottom electrode and Al top electrode were fabricated and investigated. The main research work of this paper are as follows: 1. 9-[4’-bromo-(1,1’-biphenyl)-4-ylmethyl]-9H-carbazole-3,6-diamine was synthesized by usingcarbazole as the starting material. A series of new aromatic diamines were synthesized by reacting of 9-[4’-bromo-(1,1’-biphenyl)-4-yl]methyl-9H-carbazole-3,6-diamine with kinds of arylboronic acid. The diamines and related intermediates were characterized by means of FT-IR,1H NMR, 13 C NMR and elemental analysis, respectively. 2. A series of new polyimides were synthesized using eight new aromatic diamines reacting with three aromatic dianhydrides by a two-step polycondensation. All polyimides show preferable thermal properties. The glass transition temperatures are in the range from 200 to 310 °C and the temperatures of 10 % gravimetric losses of the polyimides reach over 430 °C under nitrogen. The residual yields at 900 °C for all the polymers are above 60 wt %. The polymers exhibit perfect solubility and optical property due to introduction of fluorine. As potential organic memory materials, we analysised these polyimides by cyclic voltammetry curves, quantum calculation and memory characteristics.